Causes of Death, Australia methodology

This publication contains statistics on causes of death for Australia, together with selected statistics on perinatal deaths.

Statistics on perinatal deaths for the 2007-2009 reference years were published separately in Perinatal Deaths, Australia, 2009 (cat. no. 3304.0).

Information in Causes of Death, Australia is not comparable with deaths data published in the monthly Provisional Mortality Statistics reports which provides preliminary counts of deaths by date of occurrence in 2021.

In order to complete a death registration, the death must be certified by either a doctor using the Medical Certificate of Cause of Death, or by a coroner. In 2021, 87.7% of deaths were certified by a doctor. The remaining 12.3% were certified by a coroner. There are variations between jurisdictions in relation to the proportion of deaths certified by a coroner, ranging from 6.9% of deaths certified by a coroner and registered in Queensland, to 25.4% of deaths certified by a coroner and registered in the Northern Territory.

In order to complete a perinatal death registration, the death must be certified by either a doctor, using the Medical Certificate of Cause of Perinatal Death, or by a coroner. In 2021, 97.6% of perinatal deaths were certified by a doctor, with the remaining 2.4% certified by a coroner. 

It is the role of the coroner to investigate the circumstances surrounding all reportable deaths and to establish, wherever possible, the circumstances surrounding the death, and the cause(s) of death. Although there is variation across jurisdictions in what constitutes a death that is reportable to a coroner, they are generally reported in circumstances such as:

• where the person died unexpectedly and the cause of death is unknown
• where the person died in a violent or unnatural manner
• where the person died during, or as a result of an anaesthetic
• where the person was 'held in care' or in custody immediately before they died
• where the identity of the person who has died is unknown.

The registration of deaths is the responsibility of the eight individual state and territory Registries of Births, Deaths and Marriages. As part of the registration process, information about the cause of death is supplied by the medical practitioner certifying the death or by a coroner. Other information about the deceased is supplied by a relative or other person acquainted with the deceased, or by an official of the institution where the death occurred. The information is provided to the Australian Bureau of Statistics (ABS) by individual registries for coding and compilation into aggregate statistics. In addition, the ABS supplements this data with information from the National Coronial Information System (NCIS). As a voluntary collaboration between the Australian States and Territories and New Zealand, the NCIS is independent of the coronial system and does not form any part of the coronial investigation process. The NCIS enables access to some documents from the coronial investigation but it is not intended to be a full replica of the coronial brief.

The diagram below outlines the Australian Causes of Death Statistics System. Each death is certified by either a doctor or coroner and the resultant information is provided to the Australian Bureau of Statistics (ABS) through the Registrar of Births, Deaths and Marriages in each state or territory. Information is also provided via the National Coronial Information System for those deaths certified by a coroner. The ABS processes, codes and validates this information, which is then provided in statistical outputs.

Ideally, for compiling annual time series, the number of deaths should be recorded and reported as those which occurred within a given reference period, such as a calendar year. However, there can be lags in the registration of deaths with the state or territory registries and so not all deaths are registered in the year that they occur. There may also be further delays to the ABS receiving notification of the death from the registries due to processing or data transfer lags. Therefore, every death record will have:

• a date on which the death occurred (the date of occurrence)
• a date on which the death is registered with the state and territory registry (date of registration)
• a date on which the registered death is lodged with the ABS and deemed in scope.

With exception to the statistics published by Year of Occurrence (Data Cube 14), all deaths referred to in this publication relate to the number of deaths registered, not those which actually occurred, in the years shown.

The scope for each reference year of the death registrations includes:

• deaths registered in the reference year and received by the ABS in the reference year
• deaths registered in the reference year and received by the ABS in the first quarter of the subsequent year
• deaths registered in the years prior to the reference year but not received by ABS until the reference year or the first quarter of the subsequent year, provided that these records have not been included in any statistics from earlier periods.

From 2007 onwards, data for a particular reference year includes all deaths registered in Australia for the reference year that are received by the ABS by the end of the March quarter of the subsequent year. Death records received by the ABS during the March quarter of 2022 which were initially registered in 2021 (but for which registration was not fully completed until 2022) were assigned to the 2021 reference year. Any registrations relating to 2021 which were received by the ABS from April 2022 will be assigned to the 2022 reference year. Approximately 5% to 8% of deaths occurring in one year are not registered until the following year or later. 

Prior to 2007, the scope for the reference year of the Death Registrations collection included:

• deaths registered in the reference year and received by the ABS in the reference year
• deaths registered in the reference year and received by the ABS in the first quarter of the subsequent year
• deaths registered during the two years prior to the reference year but not received by the ABS until the reference year.

The ABS Causes of Death collection includes all deaths that occurred and were registered in Australia, including deaths of persons whose usual residence was overseas. Deaths of Australian residents that occurred outside Australia may be registered by individual registries, but are not included in ABS deaths or causes of death statistics.

The current scope of the statistics includes:

• all deaths being registered for the first time
• deaths in Australia of temporary visitors to Australia
• deaths occurring within Australian Territorial waters
• deaths occurring in Australian Antarctic Territories or other external territories (including Norfolk Island)
• deaths occurring in transit (i.e. on ships or planes) if registered in the Australian state or territory of 'next port of call'
• deaths of Australian Nationals overseas who were employed at Australian legations and consular offices (i.e. deaths of Australian diplomats while overseas) where able to be identified
• deaths that occurred in earlier reference periods that have not been previously registered (late registrations).

The scope of the statistics excludes:

• repatriation of human remains where the death occurred overseas
• deaths of foreign diplomatic staff in Australia (where these are able to be identified) 
• stillbirths/fetal deaths (these are included in perinatal death statistics (see Perinatal deaths, below)). In 2007-2009 these were published separately in Perinatal Deaths, Australia (cat. no. 3304.0) but are now included in this publication.

Deaths registered on Norfolk Island from 1 July 2016 are included in this publication. This is due to the introduction of the Norfolk Island Legislation Amendment Act 2015. Norfolk Island deaths are included in statistics for "Other Territories" as well as totals for all of Australia. Deaths registered on Norfolk Island prior to 1 July 2016 were not in scope for death statistics. Prior to 1 July 2016, deaths of people that occurred in Australia with a usual residence of Norfolk Island were included in Australian totals, but assigned a usual residence of 'overseas'. With the inclusion of Norfolk Island as a territory of Australia in the Australian Statistical Geography Standard (ASGS) 2016, those deaths which occurred in Australia between January and June 2016 with a usual residence of Norfolk Island were allocated to the Norfolk Island SA2 code instead of the 'overseas' category.  

This publication draws extensively on information provided freely by the state and territory Registries of Births, Deaths and Marriages, and the Victorian Department of Justice who manage the National Coronial Information System (NCIS). Their continued cooperation is very much appreciated: without it, the wide range of vitals statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.

From the Causes of Death Australia, 2015 publication, data has been released approximately six months earlier than previous issues (2014 and prior). This was due to a number of improvements in the processing of demographic and cause of death information.

In compiling causes of death statistics, the ABS employs a variety of measures to improve quality, which include:

• providing certifiers with certification booklets for guidance in reporting causes of death on medical certificates, see Information Paper: Cause of Death Certification Australia, 2008
• seeking detailed information from the National Coronial Information System (NCIS)
• editing checks at the individual record and aggregate levels.

The number of deaths registered in 2021 (171,469) increased by 10,169 compared to 2020 registrations. All jurisdictions recorded an increase in death registrations in 2021. This follows lower death counts in  2020, after the introduction of public health measures to limit the spread of COVID-19.

Deaths that are referred to a coroner can take time to be fully investigated, which subsequently affects the availability of data to the ABS for cause of death coding. Each year, some coroner cases are coded by the ABS before the coronial proceedings are finalised. Coroner cases that have not been closed or had all information made available can impact on data quality as less specific ICD codes often need to be applied.

At the time of coding 2021 data, there was a higher proportion of open coroner cases than at the time of preliminary coding in previous years (67.2% in 2021 versus a 5-year average for 2015-2019 of 56.2%). This is reflected in the 2021 dataset by a higher proportion of deaths due to Other ill-defined and unspecified causes of mortality (R99). Cases coded to R99 made up 9.8% of the coroner certified deaths dataset in 2021, compared with a historical average of 6.3%. Of these cases, 74.6% are open cases that fall within the scope of the ABS causes of death revisions process.

Causes of death data for 2021 would ordinarily be revised in early 2024. In light of the information detailed above, an early revision of 2021 data will be conducted during the upcoming revisions cycle in 2023. This revision will target open cases currently coded to Other ill-defined and unspecified causes of mortality (R99), Exposure to unspecified factor (X59) and Unspecified event, undetermined intent (Y34), with the aim of enhancing the specificity of the codes applied to these cases by capturing additional coronial information made available since initial coding.

Causes of death with a high proportion of coroner certified deaths (e.g., suicide, assault, drug-induced deaths) should be interpreted with caution due to the expectation that these data will change during revisions.

Drug-induced deaths are those which are directly attributable to drug use. They include deaths due to acute drug toxicity (e.g. overdose) and chronic drug use (e.g. drug-induced cardiac conditions).

On average, 97% of drug-induced deaths are certified by a coroner. There are multiple complex factors which need to be considered when a death is certified as drug-induced. The timing between the death and toxicology testing can influence the levels and types of drugs detected, making it difficult to determine the true level of a drug at the time of death. Individual tolerance levels may also vary considerably depending on multiple factors, including sex, body mass and a person’s previous exposure to a drug. Contextual factors around the death must also be considered such as pre-existing natural disease and reports from informants (e.g., friends and families) regarding the circumstances surrounding death. For these reasons, the certification of a death as being drug-induced can take significant time to complete, making these deaths particularly sensitive to the revisions process. 

Drug-induced deaths data is preliminary for 2021 and 2020 - interpretation should take into account that numbers of drug-induced deaths will increase when the ABS revisions process is applied. Revised data for drug-induced deaths in 2021 will be published in early 2023. 

As a result of two reconciliation exercises conducted jointly between the ABS and the Victorian Registry of Births Deaths and Marriages (Victorian RBDM), additional historical death registrations have been added to mortality dataset. This was due to an issue associated with the Registry's previous processing system (replaced in 2019) which resulted in some death registrations not being delivered to the ABS in the year they were registered. 

The first exercise (conducted in the first quarter of 2020) resulted in the identification of an additional 2,812 death registrations from 2017 to 2019 that had not previously been provided to the ABS. Of these, 40.4% were registered in 2017, 57.0% in 2018 and the remainder in 2019 (2.6%). The 2,812 Victorian deaths were in scope of the 2019 reference year and therefore included in 2019 counts of total deaths in both the Deaths, Australia, 2019 and Causes of Death, Australia, 2019 datasets.

Of the 2,739 deaths that were registered in 2017 and 2018 and submitted to the ABS for the 2019 reference year 62.9% were certified by a coroner with the remaining 37.1% certified by a doctor. This led to an increase across a number of causes of death, with those more likely to be referred to a coroner (i.e. external causes of death) experiencing larger effects from the delayed delivery of registrations. A time series adjustment was applied to deaths due to suicide, assault and accidental drug overdose to enable a more accurate comparison of mortality over time for these causes. See Technical note: Victorian additional registrations and time series adjustments in Causes of Death, Australia, 2019 for detailed information on this issue. 

In order to present a more accurate time series, where historical data is presented for Victoria for the years 2017-2019 in the commentary in this publication, the Victorian additional registrations from this first reconciliation exercise have been presented by year of registration across all causes (not just the three causes of suicide, assault and accidental drug overdose). Numbers presented in the commentary may therefore differ from numbers presented in the data cubes and components may not add up to totals.

A subsequent exercise (conducted in the first quarter of 2022) identified a further 1,864 death registrations from 2013 to 2016 that had not previously been provided to the ABS. Of these, 31.7% were registered in 2013, 24.6% in 2014, 7.7% in 2015 and the remainder in 2016 (36.1%). As these deaths occurred more than five years prior to the 2021 reference year, they are not considered to be representative of mortality in 2021 and are excluded from the 2021 reference year counts. In the Deaths, Australia, 2021 publication these additional registrations have been included in tables that are presented by year of occurrence of death only. 

There were 72 deaths of these 1,864 registrations that were due to suicide. These 72 deaths due to suicide have been included according to the year of registration in relevant data tables and commentary. All other registrations are included in year of occurrence outputs only. See Technical note: Victorian additional registrations (2013-2016) for more details on these registrations and how they are reflected in published data. 

Additionally, as part of the implementation of the new registration system in Victoria in February 2019, there was a change in the way coroner referred deaths are reported to the ABS. Previously there was a range of factors that would determine the point at which a coroner referred death was reported to the ABS, often leading to significant delays in reporting. From 2019, this changed and interim registrations (open cases) have been submitted to the ABS resulting in more timely delivery of death registration information to the ABS.

An issue has been identified with cause of death data for Western Australia where some information was not uploading in full to the ABS Mortality processing system. The issue mostly impacts associated cause data for doctor certified deaths in Western Australia from 2016 forward. 2021 data has been updated, and revised data for 2016 to 2020 will be provided in a future update to the 2021 Causes of Death publication. 

Traditionally coroner referred deaths are in scope for revision twice after initial publication, with the latest revision cycle having included finalising 2018 and the first revision of 2019 reference year data. Throughout the coding year 67 coroner referred deaths in the 2017 reference year with an underlying cause due to Other ill-defined and unspecified causes of mortality (R99) were identified to have an updated cause of death description, which would lead to assigning a more specified underlying cause of death.

See the Data quality section of the methodology and Causes of Death Revisions, 2018 Final Data (Technical Note) and 2019 Revised Data (Technical Note) in Causes of Death, Australia, 2020 for more information surrounding the revisions process.

The table below outlines the causes of death the 67 deaths are now assigned to. The majority of deaths (94%) were reassigned to specific natural causes of death (A00-R95), with 29 being reassigned to the Diseases of the circulatory system (I00-I99). Four deaths were reassigned to an external cause.

In 2016 and 2017 there were lower than expected registration counts for New South Wales. The ABS worked with the NSW Registry of Births, Deaths and Marriages (NSW RBDM) to investigate these counts, highlighting that changes to identity requirements in 2016 had prevented some registrations from being finalised. The NSW RBDM worked with parents to finalise these registrations, enabling many to be included in 2018 counts. Other initiatives also contributed to the higher count of births in NSW in 2018, including the implementation of an online birth registration system and a campaign aimed at increasing registrations among Aboriginal and Torres Strait Islander parents.

In 2018, the Northern Territory Registry of Births, Deaths and Marriages identified a processing issue that led to delays in completing the registration of some births that occurred in previous years. These births have since been registered, resulting in 355 additional births being included in 2018 data, the majority of which (339) were of Aboriginal and Torres Strait Islander children. Care should be taken when interpreting changes in birth counts, infant death rates and fertility rates for the Northern Territory in recent years.

In 2020, lockdowns due to the COVID-19 pandemic influenced the number of birth registrations in Australia, with fewer births registered in 2020 compared to recent years. 

In November 2010, the Queensland Registrar of Births, Deaths and Marriages advised the ABS of an outstanding deaths registration initiative undertaken by the registry. This initiative resulted in the November 2010 registration of 374 previously unregistered deaths which occurred between 1992 and 2006 (including a few for which a date of death was unknown). Of these, around three-quarters (284) were deaths of Aboriginal and Torres Strait Islander Australians. A data adjustment is made for tables which include Aboriginal and Torres Strait Islander data for Queensland for 2010. For further information refer to Technical Notes, Registration of Outstanding Deaths, Queensland, 2010 in Deaths, Australia, 2010 and Retrospective Deaths by Causes of Death, Queensland, 2010, in Causes of Death, Australia, 2010.

In September quarter 2011 the high number of death registrations in New South Wales was queried with the New South Wales Registry of Births, Deaths and Marriages. Information provided by the Registry indicates that these fluctuations may be the result of changes in processing rates. This may have contributed to the increase in the number of deaths registered in New South Wales in 2011. New South Wales deaths in 2011 (50,182) were 5.8% higher than in 2010 (47,453).

For coroner certified deaths, the specificity of cause of death coding can be affected by the length of time for the coronial process to be finalised and the coroner case closed. To improve the quality of ICD coding, all coroner certified deaths registered after 1 January 2006 are subject to a revisions process.

Up to and including deaths registered in 2005, ABS Causes of Death processing was finalised at a point in time. At this point, not all coroners' cases had been investigated, the case closed and relevant information loaded into the National Coronial Information System (NCIS). The coronial process can take several years if an inquest is being held or complex investigations are being undertaken. In these instances, the cases remain open on the NCIS and relevant reports may be unavailable. Coroners' cases that have not been closed or had all information made available can impact on data quality as less specific ICD codes often need to be applied.

The revisions process to date has focused on cases that remain open on the NCIS database. ABS coders investigate and use additional information from police reports, toxicology reports, autopsy reports and coroners' findings to assign more specific causes of death. The use of this additional information occurs at either 12 or 24 months after initial processing and the specificity of the assigned ICD-10 codes increase over time. As 12 or 24 months pass after initial processing, many coronial cases are closed, with the coroner having dispensed a cause of death and relevant reports have been made available. This allows ABS coders to assign a more specific cause of death.

These published outputs include 2021 and 2020 preliminary data, and 2019 revised data. Data for reference years up to and including 2018 are considered final and no longer subject to the revisions process. Final data for 2019 and revised data for 2020 will be released in early 2023.

Data cells with small values have been randomly assigned to protect confidentiality. As a result some totals will not equal the sum of their components. Cells with 0 values have not been affected by confidentialisation.

Where figures have been rounded, discrepancies may occur between totals and sums of the component items.

ABS published outputs are available free of charge from the ABS website. Click on 'Statistics' to gain access to the full range of ABS statistical and reference information. For details on products scheduled for release in the coming week, click on the Future Releases link on the ABS homepage.

A range of socio-demographic data is available from the ABS Causes of Death collection including age, sex, and Aboriginal and Torres Strait Islander origin. This data has been coded and presented on standard classifications developed by the ABS. Where these are not released in the Causes of Death published outputs, they can be sourced on request from the ABS. 

The Aboriginal and Torres Strait Islander origin is captured through the death registration process and coded and presented in this publication based on the ABS Indigenous Status classification, see Indigenous Status Standard, 2014.

Since the publication of Causes of Death, Australia, 2011, the ABS has released data based on the Australian Statistical Geography Standard (ASGS). The ASGS is a hierarchical classification system that defines more stable, consistent and meaningful areas than those of the Australian Standard Geographical Classification (ASGC), which was used to define geographical areas for output prior to the release of 2011 reference year data. Under the ASGS, the usual residence of the deceased is coded to the meshblock level. For further information, refer to the Australian Statistical Geography Standard (ASGS) Edition 3, July 2021 - June 2026. 

Causes of death statistics are presented at the state/territory and national level in this publication. These statistics have been compiled based on the state or territory of usual residence of the deceased, regardless of where in Australia the death occurred and was registered. Deaths of persons usually resident overseas which occur in Australia are included in the state/territory in which their death was registered. Usual residence data at the sub-state level for 2001 to 2020 has been revised to reflect the 2021 version of the ASGS. 

The country of birth of the deceased is coded and presented based on the Standard Australian Classification of Countries (SACC). Deaths coded according to the SACC reflect the country of birth of the deceased, as opposed to ancestry. This classification groups neighbouring countries into progressively broader geographic areas on the basis of their similarity in terms of social, cultural, economic and political characteristics. For further information, refer to the Standard Australian Classification of Countries (SACC).

The International Classification of Diseases (ICD) is the international standard classification for epidemiological purposes and is designed to promote international comparability in the collection, processing, classification, and presentation of causes of death statistics. The classification is used to classify diseases and causes of disease or injury as recorded on many types of medical records as well as death records. The ICD has been revised periodically to incorporate changes in the medical field. Currently the ICD 10th revision is used for Australian causes of death statistics.

The ICD-10 is a variable-axis classification meaning that the classification does not group diseases only based on anatomical sites, but also on the type of disease. Epidemiological data and statistical data is grouped according to:

• epidemic diseases
• constitutional or general diseases
• local diseases arranged by site
• developmental diseases
• injuries.

For example, a systemic disease such as sepsis is grouped with infectious diseases; a disease primarily affecting one body system, such as a myocardial infarction, is grouped with circulatory diseases; and a congenital condition, such as spina bifida, is grouped with congenital conditions.

For further information and access to versions of the ICD refer to WHO International Classification of Diseases (ICD).

The Update and Revision Committee (URC), a WHO advisory group on updates to ICD-10, maintains the cumulative and annual lists of approved updates to the ICD-10 classification. The updates to ICD-10 are of numerous types including the addition and deletion of codes, changes to coding instructions and modification and clarification of terms.

From the 2013 reference year, the ABS implemented a new automated coding system called Iris. The 2013-2021 data coded in the Iris system applied updated versions of the ICD-10 when coding multiple causes of death, and when selecting the underlying cause of death. The 2021 reference year causes of death data presented in this publication was coded using version 5.8.0 of Iris software which applied the WHO ICD-10 updates (2020 version). For coding of 2021 data, the dictionary was updated to reflect new codes added including for vaccine deaths and long COVID-19. More information on Iris and ICD-10 versioning can be found in the table below. For details of further impacts of this change from 2013 data onwards, see the ABS Implementation of the Iris Software: Understanding Coding and Process Improvements Technical Note, in the Causes of Death, Australia, 2013 publication.

In response to the COVID-19 pandemic, the World Health Organization (WHO) issued the ICD emergency codes U07.1 COVID-19, virus identified and U07.2 COVID-19, virus not identified. A death directly due to COVID-19 is defined by the WHO as a death resulting from a clinically compatible illness, in a probable or confirmed COVID-19 case, unless there is a clear alternative cause of death that cannot be related to COVID disease (e.g. trauma). There should be no period of complete recovery from COVID-19 between illness and death. 

In 2021, COVID-19 vaccinations were introduced globally. The World Health Organization subsequently issued the ICD-10 emergency code U12.9 (COVID-19 vaccines causing adverse effects in therapeutic use, unspecified) to capture adverse effects of COVID-19 vaccines in therapeutic use. This code allows COVID-19 vaccine-related deaths to be identified separately from deaths involving adverse reactions to other vaccines and biological substances. 

In summary, the following new emergency codes have been issued by WHO since 2020 in response to the emergence of COVID-19 to be used when coding causes of death for statistical purposes: 

• U07.1 COVID-19 virus identified - This code is used when COVID-19 is confirmed by laboratory testing.
• U07.2 COVID-19 virus not identified - This code is used for suspected or clinical diagnoses of COVID-19 where testing is not completed or inconclusive.
• U08 Personal history of COVID-19 - This code is used when a person has recovered from COVID-19 and no long-term effects have been certified as contributing to an individual’s death and/or COVID-19 is listed on the death certificate but it did not contribute to the death. These deaths are not included in COVID-19 mortality tabulations.
• U09 Post COVID-19 condition -This code is used to link long term conditions including chronic lung conditions that are the result of the virus. These deaths are included in COVID-19 mortality tabulations as associated causes of death. 
• U10 Multisystem inflammatory syndrome associated with COVID-19 - This code is used to identify people who have died from COVID-19 where the virus has led to a multi-inflammatory response syndrome. 
• U11 Need for immunization against COVID-19 - This code has been assigned to deaths where an incidental mention of a COVID-19 vaccine has been listed on the death certificate. An incidental mention is where the doctor has stated that a person recently received a vaccine but it did not have any contribution to death. 
• U12 COVID-19 vaccines causing adverse effects in therapeutic use - This code allows COVID-19 vaccine-related deaths to be identified separately from deaths involving adverse reactions to other vaccines and biological substances.

A further code ‘Z03.8 Examination for observation and other specified reasons’ can be used to record a negative test result in order to capture this information on the death certificate. These deaths are not tabulated as being due to COVID-19. 

With the introduction of 2019 ICD-10 updates there was a change to the code for deaths due to poisoning by and exposure to carbon monoxide and other gases and vapours. This change was applied to poisoning across multiple intents including accident (X47), intentional (X67), assault (X88) and undetermined intent (Y17). There are now multiple fourth-digit options for X47, X67, X88 and Y17. Previously, when a death occurred as a result of poisoning by and exposure to carbon monoxide and other gases and vapours, there was no option to further identify carbon monoxide from other gases and vapours as well as to specify the source of the carbon monoxide. ABS mortality coders are now required to choose from multiple fourth-digit options to further specify the death:

• X47.0/X67.0/X88.0/Y17.0 carbon monoxide from combustion engine exhaust 
• X47.1/X67.1/X88.1/Y17.2 carbon monoxide from utility gas
• X47.2/X67.2/X88.2/Y17.2 carbon monoxide from other domestic fuels
• X47.3/X67.3/X88.3/Y17.3 carbon monoxide from other sources
• X47.4/X67.4/X88.4/Y17.3 carbon monoxide from unspecified sources 
• X47.8/X67.8/X88.8/Y17.8 other specified gases and vapours 
• X47.9/X67.9/X88.9/Y17.9 unspecified gases and vapours 

Prior to the 2013 reference year, the 2006 version of the ICD-10 was the most recent version used for coding deaths, with the exception of two updates that were applied after the 2006 reference year. The first update was implemented in 2007 and related to the use of mental and behavioural disorders due to psychoactive substance use, acute intoxication (F10.0, F11.0...F19.0) as an underlying cause of death. If the acute intoxication initiated the train of morbid events it is now assigned an external accidental poisoning code (X40-X49) corresponding to the type of drug used. For example, if the death had been due to alcohol intoxication, the underlying cause before the update was F10.0, and after the update the underlying cause is X45, with poisoning code T51.9. The second update implemented from the 2009 reference year was the addition of Influenza due to certain identified virus (J09) to the Influenza and Pneumonia block. This addition was implemented to capture deaths due to Swine flu and Avian flu, which were reaching health epidemic status worldwide.

The cumulative list of ICD-10 updates can be found online.

Conditions on the medical certificate of cause of death are coded to the International Classifications of Diseases, 10th revision (see Classifications section of the methodology for more information). All causes of death can be grouped to describe the type of death, whether it be from a disease or condition, or from an injury, or whether the cause is unknown. These are generally described as:

• Natural Causes - deaths due to diseases (for example diabetes, cancer, heart disease etc.) (A00-Q99, R00-R98)
• External Causes - deaths due to causes external to the body (for example intentional self-harm, transport accidents, falls, poisoning etc.) (V01-Y98)
• Unknown Causes - deaths where it is unable to be determined whether the cause was natural or external (R99).

Where an accidental or violent death occurs, the underlying cause is classified according to the circumstances of the fatal injury, rather than the nature of the injury, which is coded separately. For example, a motorcyclist may crash into a tree (V27.4) and sustain multiple fractures to the skull and facial bones (S02.7), which leads to death. The underlying cause of death is the crash itself (V27.4), as it is the circumstance which led to the injuries that ultimately caused the death.

From the 2013 reference year, the ABS implemented a new automated coding system called Iris. The 2013-2021 data coded in the Iris system applied updated versions of the ICD-10 when coding multiple causes of death, and when selecting the underlying cause of death. The 2021 reference year causes of death data presented in this publication was coded using version 5.8.0 of Iris software which applied the WHO ICD-10 updates (2020 version). For coding of 2021 data, the dictionary was updated to reflect new codes added including for vaccine deaths and long COVID-19. More information on Iris and ICD-10 versioning can be found in the table below. For details of further impacts of this change from 2013 data onwards, see the ABS Implementation of the Iris Software: Understanding Coding and Process Improvements Technical note, in the Causes of Death, Australia, 2013 publication and Updates to Iris coding software: Implementing WHO updates and improvements in coding processes Technical note, in the Causes of Death, Australia, 2018 publication.

The quality of causes of death coding can be affected by changes in the way information is reported by certifiers, by lags in completion of coroner cases and the processing of the findings. While changes in reporting and lags in coronial processes can affect coding of all causes of death, those coded to Chapter XVIII: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified and Chapter XX: External causes of morbidity and mortality are more likely to be affected because the code assigned within the chapter may vary depending on the coroner's findings (in accordance with ICD-10 coding rules).

Where a case remains open on the NCIS at the time the ABS ceases processing, and insufficient information is available to code a cause of death (e.g. a coroner certified death was yet to be finalised by the coroner), less specific ICD codes are assigned, as required by the ICD coding rules.

The specificity with which open cases are able to be coded is directly related to the amount and type of information available on the NCIS. The amount of information available for open cases varies considerably from no information to detailed police, autopsy and toxicology reports. There may also be interim findings of 'intent'.

The manner or intent of an injury which leads to death, is determined by whether the injury was inflicted purposefully or not. When it was inflicted purposefully (intentional), a determination should be made as to whether the injury was self-inflicted (suicide) or inflicted by another person (assault). However, intent cannot be determined in all cases.

ICD-10 codes are assigned to all conditions on a medical certificate of cause of death and rules applied to select an underlying cause of death. The WHO defines the underlying cause of death as the disease or injury that initiated the train of morbid events leading directly to death. Accidental and violent deaths are classified according to the external cause, that is, to the circumstances of the accident or violence which produced the fatal injury rather than to the nature of the injury. The majority of data presented in the data cubes in this publication is tabulated according to the underlying cause of death. 

Multiple causes of death include all causes and conditions reported on the death certificate (i.e. both underlying and associated causes; see the Glossary for further details). As all entries on the death certificate are taken into account, multiple causes of death statistics are valuable in recognising the impact of conditions and diseases which are less likely to be an underlying cause, highlighting relationships between concurrent disease processes, and giving an indication of injuries which occur as a result of specific external events. These features of multiple causes of death data provide a more in depth picture of mortality in Australia.

When analysing data on multiple causes of death, data can be presented in two ways: by counts of deaths or by counts of mentions. When analysis is conducted by counts of death, the figures are describing the number of people who have died with a particular disease or disorder. Multiple Causes of Death data derived from counts of mentions is the total number of incidences of a particular disease or disorder on the death certificate. For example, an individual may have had Breast cancer (C50) and then developed Secondary lung cancer (C78.0). This individual would be counted once if counts were by the number of deaths from cancer, but twice if the counts were by the number of mentions of cancer. Care should be taken to differentiate between counts and mentions when analysing multiple causes of death data.

Changes in patterns of mortality are studied by policy makers and researchers to improve health outcomes for all Australians. However, changes in patterns of mortality can occur for many reasons. Changes can reflect a real increase or decrease in the prevalence of a disease or disorder, or a change in medical treatment. Mortality data changes can also be a result of administrative processes which can potentially impact on the data, for example, International Classification of Disease (ICD) coding classification changes and updates, and differences in how deaths are certified. Analysis of the multiple causes of death data can give a deeper understanding of how the complete dataset may be affected by both real and administrative changes. For example, in 2009, the World Health Organization (WHO) recommended introducing code J09 (Influenza due to certain identified influenza virus) to the ICD-10 in response to the worldwide epidemics of swine flu and avian flu. There were 98 people who died as a direct consequence of contracting these strains of the flu across 2009 and 2010. In addition there were 51 people who had this flu when they died and for whom this would have been a complicating factor. Additional health risk factors may also be identified. When swine or avian flu was the underlying cause of death, multiple causes data shows obesity and respiratory problems as a common associated cause. In this way, multiple causes data provides policy makers and researchers a greater insight beyond the underlying cause of death. 

As part of a collection-wide initiative by the ABS to improve specificity of cause of death coding in the 2008 and 2009 reference years, doctor certified deaths due to Pneumonia, organism unspecified (J18) reduced substantially. This was as a result of the ABS manually interrogating conditions located in Part 2 of the Medical Certificate Cause of Death (MCCD), reallocating them to a more specific cause of death code.

In 2010 there was a shift in this pattern. The number of doctor certified deaths assigned to J18 increased by 690 deaths, or 49.5%. The reason for the 2010 data movement was a more consistent use of coding software decision tables throughout both coding and quality assurance processes. These decision tables provide clear rules for when Pneumonia can be selected as an underlying cause of death, in relation to the information listed in Part 2 of the MCCD.

The 2010 increase represented a return to counts observed prior to 2008. In 2007, 2,293 doctor certified deaths were assigned to J18, therefore the 2010 count for this cause of death (2,085) is considered a return to the trend which existed prior to the coding of 2008 and 2009 data. The data from 2011 onwards has been consistent with this trend.

There were 1,264 deaths attributed to road crashes (V01-V79, V89.2, X82, Y32) in 2021. Of these, 41 were of suicidal intent (X82) and there were a further 17 where the intent could not be determined (Y32). When making comparisons between road deaths from the ABS Causes of Death collection and road deaths from other sources, the scope and coverage rules applying to each collection should be considered. It should be noted that the number of road-traffic-related deaths attributed to transport accidents for 2021 is expected to change as data is subject to the revisions process.

There were 77 transport accidents (V00-V99) that were registered in Victoria in 2017 and 2018 but not supplied to the ABS as an official death registration until 2019. These 77 deaths are included in the 2019 reference year data for Victoria and Australia totals of transport accidents. For more information refer to Technical note: Victorian additional registrations and time series adjustments in Causes of Death, Australia, 2019. 

The number of deaths attributable to Accident to watercraft causing drowning and submersion (V90) increased from 26 in 2010 to 75 in 2011. This increase is primarily due to deaths resulting from an incident in December 2010 when a boat collided with cliffs on Christmas Island. These deaths were registered with the Western Australian Registry of Births, Deaths and Marriages in January 2011, resulting in an increase in the number of deaths coded to V90 in Western Australia.

The number of deaths recorded as Assault (X85-Y09, Y87.1) i.e. murder, manslaughter and their sequelae, published in the ABS Causes of Death publication, differ from those published by the ABS in Recorded Crime - Victims, Australia. Reasons for the different counts include differences in scope and coverage between the two collections, as well as legal proceedings that are pending finalisation. It is important to note that the number of deaths attributed to assault for 2021 is expected to change as data is subject to the revisions process. See Causes of Death Revisions, 2018 Final Data (Technical Note) and 2019 Revised Data (Technical Note) in Causes of Death, Australia, 2020.

There were 28 deaths due to assault that were registered in Victoria in 2017 (13 deaths) and 2018 (15 deaths) that were not submitted to the ABS until the 2019 reference year. These deaths are included in the total number of all cause deaths for 2019 in line with ABS scope of mortality data. When analysing assaults as an individual cause of death a time series adjustment has been applied and these 28 deaths have been reassigned to their respective registration years in the data cubes of this publication. 

The source of all cause of death data for the ABS is collected through the civil registration system either by the Medical Certificate of Cause of Death (MCCD) for doctor certified deaths or the pathology report or coronial findings for coroner referred deaths (accessed via the National Coronial Information System). This enables identification of the underlying cause of death and other associated causes. Civil registration based data is not directly comparable with that released from disease surveillance systems which are designed to release information rapidly on both infections and mortality. Information about mortality sourced from the registration-based system takes longer to receive than information reported through the surveillance system, but it is more comprehensive and can provide important additional insights into deaths from COVID-19. 

The civil registration system also captures deaths which may be caused by the COVID-19 vaccine. Deaths due to the vaccine identified by the ABS are certified by a medical practitioner or a coroner. Independent analysis and interpretation of deaths data by authorities such as the Therapeutic Goods Administration (TGA) is not conveyed to the ABS or reflected in coding outputs. Due to the scope of the ABS deaths collection, data received and published by the ABS may differ from data collected through the TGA's independent investigations into COVID-19 vaccine-related deaths.

Ranking causes of death is a useful method of describing patterns of mortality in a population and allows comparison over time and between populations. However, different methods of grouping causes of death can result in a vastly different list of leading causes for any given population. A ranking of leading causes of death based on broad cause groupings such as 'cancers' or 'heart disease' does not identify the leading causes within these groups, which is needed to inform policy on interventions and health advocacy. Similarly, a ranking based on very narrow cause groupings or including diseases that have a low frequency, can be meaningless in informing policy.

Tabulations of leading causes presented in this publication are based on research presented in the Bulletin of the World Health Organization, Volume 84, Number 4, April 2006, 297-304. The determination of groupings in this list is primarily driven by data from individual countries representing different regions of the world. Other groupings are based on prevention strategies, or to maintain homogeneity within the groups of cause categories. Since the aforementioned bulletin was published, a decision was made by WHO to include deaths associated with the H1N1 influenza strain (commonly known as swine flu) in the ICD-10 classification as Influenza due to certain identified influenza virus (J09). This code has been included with the Influenza and Pneumonia leading cause grouping in the Causes of Death publication since the 2009 reference year.

Since 2015, the ABS includes C26.0 (malignant neoplasm of the intestinal tract, part unspecified) in the WHO leading cause grouping for Malignant neoplasm of colon, sigmoid, rectum and anus (now C18-C21, C26.0). For further details on the reasoning behind the inclusion of C26.0 in this leading cause grouping, see Complexities in the measurement of bowel cancer in Australia, in Causes of Death, Australia, 2015. This change has been applied in this publication to data for all reference years that appear in tables involving leading cause tabulations. This differs to publications prior to 2015, for which C26.0 was not included in this leading cause grouping, and also differs to the suggested WHO tabulation of leading causes for these cancers. Comparisons with data for this leading cause, and associated leading cause rankings, as they appear in previous publications should therefore be made with caution. Time-series data by leading causes has been published in Australia's leading causes of death in this publication.

The ABS now includes Y87.0 (Sequelae of intentional self-harm), Y87.1 (Sequelae of assault) and Y85 (Sequelae transport accidents) in the WHO leading cause grouping for Intentional self-harm (now X60-X84, Y87.0), Assault (now X85-Y09, Y87.1) and Land transport Accidents (V01-V89, Y85). This change has been applied to harmonise data between the WHO leading cause grouping and subject specific data cubes for intentional self-harm, assault and transport accidents which is published as part of the ABS Causes of Death collection. This change applies to publication data for all reference years that appear in tables involving leading cause tabulations. This differs to previous publications, where Y87.0, Y87.1 and Y85 were not included in these leading cause groupings, and also differs to the suggested WHO tabulation of leading causes. Comparisons with data for these leading causes, and associated leading cause rankings, as they appear in previous publications should therefore be made with caution. Time-series data by leading causes has been published in Australia's leading causes of death in this publication.

Deaths coded to Chapter XVIII: Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99) are not included in tabulations of leading causes due to the unspecified nature of these causes. Many deaths coded to this chapter are likely to be affected by revisions, and hence recoded to more specific causes of death as they progress through the revisions process. An exception to this is Ill-defined and unknown causes of mortality (R95-R99), which is included in the analysis for deaths of those under the age of one year, as Sudden Infant Death Syndrome (R95) and Sudden Unexpected Death in Infancy (R99) is included in this cause grouping. A further exception is any comparisons between the Aboriginal and Torres Strait Islander and non-Indigenous populations. For these comparisons the Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99) grouping is included. This aligns with the WHO recommendation to include this grouping when comparing smaller populations that may have higher numbers of deaths due to this cause grouping. As deaths in this grouping are likely to be affected by revisions, the leading cause rankings may change once the data has been revised.

Age-standardised death rates enable the comparison of death rates over time and between populations of different age-structures. Along with adult, infant and child mortality rates, they are used to determine whether the mortality rate of the Aboriginal and Torres Strait Islander population is declining over time, and whether the gap between Aboriginal and Torres Strait Islander and non-Indigenous populations is narrowing. However, there have been inconsistencies in the way different government agencies have calculated age-standardised death rates in the past. The ABS uses the direct method of age-standardisation as it allows for valid comparisons of mortality rates between different study populations and across time. This method was agreed to by the ABS, Australian Institute of Health and Welfare (AIHW) and other stakeholders. For further information see: AIHW (2011) Principles on the use of direct age-standardisation in administrative data collections: for measuring the gap between Indigenous and non-Indigenous Australians. Cat. no. CSI 12. Canberra: AIHW.

The direct method has been used throughout the publication and data cubes for age-standardised death rates. Age-standardised death rates for specific causes of death with fewer than a total of 20 deaths have not been published due to issues of robustness.

For further information, see Appendix: Principles on the use of direct age-standardisation, from Deaths, Australia, 2010.

In this publication, age-standardised and age-specific death rates for all persons for the 2012-2021 reference years have been calculated using preliminary 2021 Census-based population estimates. Rates for Aboriginal and Torres Strait Islander persons for the 2012-2021 reference years have been calculated using 2016 Census-based population estimates (projections and backcasts). Non-Indigenous estimates have been derived by subtracting the 2016 Census based Aboriginal and Torres Strait Island population estimates from the total 2021 Census-based estimated resident population (ERP). Rates calculated from population denominators derived from different Censuses may cause artificially large rate differences. Rate comparisons should not be made with previous publications for Aboriginal and Torres Islander data. See Estimates and Projections, Aboriginal and Torres Strait Islander Australians for more information.

For more details on data used in calculating death rates, refer to the Appendix - data used in calculating death rates. 

The ABS accesses the National Coronial Information System (NCIS) to obtain causes of death information for coroner referred deaths including suicides. Information regarding the causes of death and associated factors is obtained from various reports including police, toxicology, autopsy and coronial findings.

The number of deaths attributed to intentional self-harm for 2021 is expected to increase as data is subject to the revisions process. At the time of coding 2021 data, there was a higher proportion of open coroner cases at preliminary coding than seen in previous years (67.2% in 2021 versus a 5-year average for 2015-2019 of 56.2%). This is reflected in the 2021 dataset by a higher rate of deaths due to other ill-defined and unspecified causes of mortality (R99). For further information, see the Data quality section of the methodology and the Causes of Death Revisions, 2018 Final Data (Technical Note) and 2019 Revised Data (Technical Note) in Causes of Death, Australia, 2020.

From 2006 onwards, the ABS implemented a revisions process for coroner certified deaths (such as suicides), which has enabled additional suicide deaths to be identified beyond initial processing. It is recognised that in the four years prior to the implementation of the revisions process (2002-2005), suicide deaths may have been understated as the ABS began using the National Coronial Information System as the sole source for coding coroner referred deaths.

In addition to the revisions process, new coding guidelines were applied for deaths registered from 1 January 2007. The new guidelines improve data quality by enabling deaths to be coded to suicide if evidence indicates the death was from intentional self-harm. Previously, coding rules required a coroner to determine a death as intentional self-harm for it to be coded to suicide. However, in some instances the coroner does not make a finding on intent. The reasons for this may include legislative or regulatory barriers around the requirement to determine intent, or sensitivity to the feelings, cultural practices and religious beliefs of the family of the deceased. Further, for some mechanisms of death it may be very difficult to determine suicidal intent (e.g. single vehicle incidents, drowning). In these cases the burden of proof required for the coroner to establish that the death was as a result of intentional self-harm may make a finding of suicide less likely.

Under the new coding guidelines, in addition to coroner-determined suicides, deaths may also be coded to suicide following further investigation of information on the NCIS. Further investigation of a death would be initiated when the mechanism of death indicates a possible suicide and the coroner does not specifically state the intent as accidental or homicidal. Information that would support a determination of suicide includes indications by the person that they intended to take their own life, the presence of a suicide note, or knowledge of previous suicide attempts. The processes for coding open and closed coroner cases are illustrated in the below diagrams (open/closed case coding decision trees).

Over time, the NCIS has worked with jurisdictions to improve the timeliness and completeness of information flowing from the coronial systems to the NCIS database. These improvements lead to changes in the information available to ABS coding staff. It is therefore important that data users are aware of any significant improvements in the management of coronial data to enable better interpretation of data within, and between, reference periods.

Coronial cases are more likely to be affected by a lag in registration time, especially those which are due to external causes, including suicide, homicide and drug-related deaths. Due to small numbers these lagged coroner referred registrations can create large yearly variation in some causes of deaths of Aboriginal and Torres Strait Islander people. Caution should be taken when making year to year analysis.

More broadly, change in administrative systems highlights how various factors (including administrative and system changes, certification practices, classification updates or coding rule changes) can impact on the mortality dataset. Data users should note this particular change and be cautious when making comparisons between reference periods. The change does not explain away differences between years, but is a factor to consider. It should also be noted as a factor that may influence the magnitude of any increases in suicide numbers as revisions are applied.

The two flow charts below highlight the guidelines used by the ABS when coding a death to intentional self-harm for open and closed coroner cases, where the intent status at the time of coding is neither intentional self-harm nor assault. In these cases, the ABS considers additional information available on NCIS, such as the mechanism and other available data (e.g. the presence of a suicide note or previous suicide attempts) when determining the intent of such deaths for coding purposes.

As a result of two reconciliation exercises conducted jointly between the ABS and the Victorian Registry of Births Deaths and Marriages (Victorian RBDM), additional historical registrations of suicide were identified that had not been previously provided to the ABS. To best reflect a more accurate time series, deaths due to suicide are presented by registration year throughout this publication. As a result, some totals may not equal the sum of their components and suicide data presented in this publication may not match that previously published by reference year. Time series adjustments have been made to Victorian suicides to more accurately reflect the pattern of registration of suicide deaths as follows:

• the first exercise (conducted in the first quarter of 2020) resulted in the identification of an additional 180 suicides that were registered in Victoria in 2017 (88 suicides) and 2018 (92 suicides) but not previously supplied to the ABS. Whilst these are included in overall total numbers of all cause deaths for 2019 in line with ABS scope rules, a time series adjustment has been made whereby these suicide deaths have been re-allocated to the year in which they were registered. See Technical note: Victorian additional registrations and time series adjustment in Causes of Death, Australia, 2019 for more information. 
• the second exercise (conducted in the first quarter of 2022) resulted in the identification of an additional 72 suicides that were registered in Victoria in 2013 (20 suicides), 2014 (14 suicides), 2015 (8 suicides) and 2016 (30 suicides) that were not previously supplied to the ABS. These registrations are not included in the total numbers of all cause deaths. However, a time series adjustment has been made whereby these suicide deaths have been re-allocated to the year in which they were registered. See Technical note: Victorian additional registrations (2013-2016) for more information. 

In 2012, the implementation of JusticeLink in the NSW coronial system significantly changed how information is exchanged between the NSW coroners courts and the NCIS. This system enables nightly uploads of all new information to the NCIS, and as a result information pertaining to NSW coronial cases is available earlier in the investigation process and the information is more complete for the purposes of coding causes of death.

There is evidence that the system change in NSW has improved the quality of preliminary coding in relation to deaths due to intentional self-harm. There has been an increase in the number of preliminary intentional self-harm deaths registered in NSW when comparing counts for 2012 onwards with those of 2011, coupled with fewer cases of deaths of undetermined intent (Y10-Y34).

The Aboriginal and Torres Strait Islander origin of a deceased person is captured through the death registration process. It is noted on the Death Registration Form and the Medical Certificate of Cause of Death. However it is recognised that not all such deaths are captured through these processes, leading to under-identification. While data is provided to the ABS for the Aboriginal and Torres Strait Islander origin of the deceased for around 99% of all deaths, there are concerns regarding the accuracy of the data.

The ABS Death Registrations collection identifies a death as being of an Aboriginal and Torres Strait Islander person where the deceased is recorded as Aboriginal, Torres Strait Islander, or both on the Death Registration Form (DRF). The Aboriginal and Torres Strait Islander origin is also derived from the Medical Certificate of Cause of Death (MCCD) for South Australia, Western Australia, Tasmania, the Northern Territory and the Australian Capital Territory from 2007. From 2015 data onwards, the Queensland Registry of Births, Deaths and Marriages also used MCCD information to derive the Aboriginal and Torres Strait Islander origin. For New South Wales and Victoria, the Aboriginal and Torres Strait Islander origin of the deceased is derived from the DRF only. If the Aboriginal and Torres Strait Islander origin reported in the DRF does not agree with that in the MCCD, an identification from either source that the deceased was an Aboriginal and/or Torres Strait Islander person is given preference over non-Indigenous or an unknown status.

There are several data collection forms on which people are asked to state whether they are of Aboriginal and Torres Strait Islander origin. Due to a number of factors, the results are not always consistent. The likelihood that a person will identify, or be identified, as an Aboriginal and Torres Strait Islander person on a specific form is known as their propensity to identify.

Propensity to identify as an Aboriginal and Torres Strait Islander person is determined by a range of factors, including:

• how the information is collected (e.g. census, survey, or administrative data);
• who provides the information (e.g. the person in question, a relative, a health professional, or an official);
• the perception of why the information is required, and how it will be used;
• educational programs about identifying as an Aboriginal and Torres Strait Islander person; and
• cultural aspects and feelings associated with identifying as Aboriginal and Torres Strait Islander Australian.

In addition to those deaths where the deceased is identified as an Aboriginal and Torres Strait Islander person, a number of deaths occur each year for which the Aboriginal and Torres Strait Islander origin is not stated on the death registration form. In 2021, there were 1,106 deaths registered in Australia for whom the Aboriginal and Torres Strait Islander origin was not stated, representing 0.6% of all deaths registered, a slight decrease from 2020 (0.7%). This difference was largely driven by fewer deaths with a not stated Aboriginal and Torres Strait Islander origin registered in New South Wales (from 538 in 2020 to 463 in 2021). 

Data presented in this publication may therefore underestimate the level of Aboriginal and Torres Strait Islander deaths and mortality in Australia. Caution should be exercised when interpreting data for Aboriginal and Torres Strait Islander Australians presented in this publication, especially with regard to year to year changes. 

Information on causes of death relating to Aboriginal and Torres Strait Islander persons is included in articles throughout this publication. Data cube 12 also provides information on causes of death for Aboriginal and Torres Strait Islander Australians. In Data cube 12, numbers and rates of death are reported by jurisdiction of usual residence for New South Wales, Queensland, South Australia, Western Australia and the Northern Territory only. Data for Victoria, Tasmania and the Australian Capital Territory has been excluded in line with national reporting guidelines. 

Individual state/territory disaggregations of deaths of Aboriginal and Torres Strait Islander Australians by WHO Leading Causes for the 2020 reference year are presented for New South Wales, Queensland, Western Australia and the Northern Territory only. No data is presented for South Australia, due to the small number of deaths by WHO leading causes - most causes have a count of fewer than 20 deaths, which is too small for the production of robust age-standardised death rates (SDRs). 

In this publication, age-standardised and age-specific death rates for Aboriginal and Torres Strait Islander persons for the 2012-2021 reference years have been calculated using 2016 Census-based population estimates (projections and backcasts). Non-Indigenous estimates have been derived by subtracting the 2016 Census-based Aboriginal and Torres Strait Islander population estimates from the total 2021 Census-based estimated resident population (ERP).  Rates calculated from population denominators derived from different Censuses may cause artificially large rate differences. Rate comparisons should not be made with previous publications for Aboriginal and Torres Islander data. See Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 2006 to 2031 for more information.

Coronial cases are more likely to be affected by a lag in registration time, especially those which are due to external causes, including suicide, homicide and drug-induced deaths. Due to small numbers these lagged coroner referred registrations can create large yearly variation in some causes of deaths of Aboriginal and Torres Strait Islander people. Caution should be taken when making year to year comparisons.

The ABS undertakes significant work aimed at improving Aboriginal and Torres Strait Islander identification. The ABS works closely with the state and territory RBDMs through the Civil Registration and Vital Statistics Australasia committee (CRVSA) to progress strategies aimed at improving Indigenous identification in a nationally consistent way.

Quality studies conducted as part of the Census Data Enhancement (CDE) project have investigated the levels and consistency of Aboriginal and Torres Strait Islander identification between the 2011 Census and death registrations. See Information Paper: Death registrations to Census linkage project - Methodology and Quality Assessment, 2011-2012 (cat. no. 3302.0.55.004).

An assessment of various methods for adjusting incomplete Aboriginal and Torres Strait Islander death registration data for use in compiling Aboriginal and Torres Strait Islander life tables and life expectancy estimates is presented in Discussion Paper: Assessment of Methods for Developing Life Tables for Aboriginal and Torres Strait Islander Australians, 2006 (cat. no. 3302.0.55.002), released on 17 November 2008. Final tables based on feedback received from this discussion paper, using information from the Census Data Enhancement (CDE) study, can be found in Life Tables for Aboriginal and Torres Strait Islander Australians, 2010-2012 (cat. no. 3302.0.55.003).

The scope of the perinatal death statistics includes all registered fetal deaths (at least 20 weeks' gestation or at least 400 grams' birth weight) and all registered neonatal deaths (all live born babies who die within 28 completed days of birth, regardless of gestation or birth weight). The ABS scope rules for fetal deaths are consistent with the legislated requirement for all state and territory Registries of Births, Deaths and Marriages to register all fetal deaths which meet the above-mentioned gestation and birth weight criteria. Based on this legislative requirement, in the case of missing gestation and/or birth weight data, the fetal record is considered in scope and included in the dataset. A record is only considered out of scope if both gestation and birth weight data are present, and both fall outside the scope criteria (i.e. gestation of 19 weeks or less and birth weight of 399 grams or fewer). This scope was adopted for the 2007 Perinatal Deaths collection, and was applied to historical data for 1999-2006. For more information on the changes in scope rules see Perinatal Deaths, Australia, 2007 (cat. no. 3304.0) Explanatory Notes 18-20. These rules have been applied to all perinatal data presented in this publication.

The World Health Organization (WHO) definition of a perinatal death differs to that used by the ABS. The WHO definition includes all neonatal deaths, and those fetuses weighing at least 500 grams or having a gestational age of at least 22 weeks. A summary table based on the WHO definition of perinatal deaths is included in the Perinatal data cube in this release. See Coding of perinatal deaths below for more details on the interpretation of this table.

Fetal deaths are registered only as a stillbirth, and are not in scope of either the Births, Australia or Deaths, Australia collections. Fetal deaths are part of the Perinatal collection, but not the Causes of Death collection. Neonatal deaths are in scope of the Deaths, Causes of Death and Perinatal collections.

Given the small number of perinatal deaths which occur in some states and territories, some data provided on a state/territory basis in this publication has been aggregated for South Australia, Western Australia, the Northern Territory, the Australian Capital Territory and Other Territories.

This publication only includes information on registered fetal and neonatal deaths. Registered deaths are sourced through jurisdictional Registries of Births, Deaths and Marriages. This scope differs from other Australian data sources on perinatal deaths. For this reason alternative datasets are not directly comparable and caution should be taken when using multiple sources for analysis.

Perinatal death data reported by the ABS is not comparable with the National Perinatal Mortality Data Collection (NPMDC) coordinated by the AIHW. The ABS data is sourced from state and territory Registries of Births, Deaths and Marriages. This differs from the NPMDC whose data is sourced from health systems, including clinical records. The table below was published in the Australia's mothers and babies: Stillbirths and neonatal deaths - Australian Institute of Health and Welfare. The table shows that the ABS perinatal dataset is affected by delayed registrations which results in an under count of perinatal deaths, especially those of stillbirths. Caution should be taken when interpreting these data.

For perinatal data output in the Causes of Death, Australia, 2013 publication, the ABS began a review of its method of coding perinatal deaths, which resulted in an interim change to how this data was output. One significant change was that neonatal deaths were not assigned an underlying cause of death when output in tables of all ages, as had previously occurred. (Details of this change can be found in the Changes to Perinatal Death Coding Technical Note in Causes of Death, Australia, 2013 (cat. no. 3303.0)). Further review and consultation has now been undertaken with the national and international coding community, and has resulted in the ABS applying a new method of coding perinatal deaths. The new method creates a sequence of causes on a Medical Certificate of Cause of Perinatal Death which allows for an underlying cause of death to be assigned to a neonatal death. This aligns the output for neonatal deaths to deaths of the general population which are certified using the Medical Certificate of Cause of Death. The change in coding method reinstates the condition arising in the mother being assigned as an underlying cause of death. This method has been applied to the 2014 data onwards, and has also been applied retrospectively to the 2013 neonatal data that is output in tables of all ages in this publication, thus enabling a consistent time-series. Please see the Changes to Perinatal Death Coding Technical Note in Causes of Death, Australia, 2014 (cat. no. 3303.0) for further details.

From the 2013 reference year onwards, process changes have led to a reduction in the number of both stillbirths and neonatal deaths where a 'main condition in mother' was recorded, compared to previous years. This has led to a reduction in the number of records assigned within the code block P00-P04: Fetus and newborn affected by maternal factors and by complications of pregnancy, labour and delivery, as main condition in the mother. These changes will affect data output in the Perinatal data cube of this publication only.

Doctor certified neonatal deaths with no causes of death information are coded to Conditions originating in the perinatal period, unspecified (P969). As these deaths have been certified by a doctor, the assumption is made that the neonate died of natural causes. Where a neonatal death is referred to a coroner, but no causes of death information is available, these deaths are coded to Other ill-defined and unspecified causes of mortality (R99). As a reportable death, it cannot be determined whether the neonate died of natural or external causes, in the absence of further information.

The count of fetal deaths in scope for the World Health Organization (WHO) definition of perinatal deaths differs to those previously published for 2012 and 2015. This is due to an enhancement to birth weight and gestation information, which resulted in some deaths no longer meeting the World Health Organization definition of a fetal death (that is, a gestational age of at least 22 weeks or weighing at least 500 grams). For 2012, there are two fewer fetal deaths than previously published (1 male and 1 female). For 2015, there are 38 fewer fetal deaths than previously published (18 males, 19 females, 1 death where sex was not specified). Some corresponding death rates have also been affected. Table 14.21 in the Perinatal data cube presents fetal and neonatal data according to the WHO scope. No other tables in the Perinatal data cube are affected by these changes.

Live births and the number of fetal deaths are used as the denominator in the calculation of mortality rates for perinatal deaths. See the 'Data Used in Calculating Death Rates' Appendix for details of the number of live births registered which have been used to calculate the fetal, neonatal and perinatal death rates shown in this publication. This Appendix also provides data on fetal deaths used in the calculation of fetal and perinatal death rates. These also enable further rates to be calculated.

In 2019 an issue was identified with the derivation of the Aboriginal and Torres Strait Islander origin for fetal deaths registered in South Australia. As a consequence, there was an undercount of Aboriginal and Torres Strait Islander fetal deaths in South Australia in ABS outputs over a number of years. The ABS worked with the SA RBDM to revise the Aboriginal and Torres Strait Islander origin of all fetal deaths for the years 2014 to 2018. Data for these years presented in Tables 19 and 20 of the Perinatal data cube in this publication was revised in the 2019 issue. 

There are a very small number of stillbirth (fetal deaths) registrations provided to the ABS each year where the sex of the infant has not  been specified as male or female. This can be due to administrative processes where the sex of the stillbirth has not been supplied to the ABS. Additionally, in a small number of births a clinical determination of sex may not be able to be clearly determined. This may be due to a number of reasons and may include extreme prematurity or some congenital conditions. Where the sex of an infant has not been specified for a stillbirth, these deaths are included in total person counts only for tabulations by fetal deaths and all perinatal deaths (both fetal and neonatal deaths). There were 18 stillbirths registered in 2021 where the sex of the infant was not specified.

1. As a result of two reconciliation exercises conducted jointly between the ABS and the Victorian Registry of Births Deaths and Marriages (Victorian RBDM), additional historical Victorian death registrations have been added to the Causes of Death dataset. This was due to an issue associated with the Registry's previous processing system (replaced in 2019) which resulted in some death registrations not being delivered to the ABS in the year they were registered. 

2. Details of the first reconciliation exercise, which resulted in an additional 2,812 death registrations from 2017 to 2019 being included in the 2019 reference year and a time series adjustment being applied to selected causes, are provided in Technical note: Victorian additional registrations and time series adjustments in Causes of Death, Australia, 2019.  

3. A subsequent exercise was conducted in the first quarter of 2022 with the aim of identifying if there were any further registrations that had not been provided to the ABS prior to 2017 as a result of the same system issue. This exercise identified a further 1,864 deaths that had been registered between 2013 to 2016 that had not previously been provided to the ABS. While these registrations are in scope for the 2021 reference year counts according to the ABS deaths collection scope (see Scope of causes of death statistics section in the methodology), they are not considered representative of 2021 deaths and have been excluded from current year counts. Instead the 1,864 death registrations are included only in outputs disseminated by year of occurrence and historical time series for deaths due to suicide. This technical note provides details of these registrations, how they are reflected in published data and time series considerations for datasets disseminated by reference year. 

4. Of the 1,864 additional deaths reported to the ABS, 31.7% were registered in 2013, 24.6% in 2014, 7.7% in 2015 and the remainder in 2016 (36.1%). These deaths occurred across the years 2012 to 2016. The table below shows the year of registration and year of occurrence of these deaths.

5. The majority of additional registrations (1,162 or 62.3%) were certified by a doctor with the remaining 702 (37.7%) certified by a coroner. The number of coroner certified deaths were over-represented in these registrations - on average annually approximately 13% to 16% of all deaths registered in Victoria are certified by a coroner. 

6. Conditions that are more likely to be certified by a coroner including external causes and ischaemic heart diseases are prevalent in the additional registrations. The table below shows the distribution of the Victorian additional registrations by ICD-10 chapter. 

7. As the additional 1,864 deaths occurred more than five years prior to the 2021 reference year, they are not considered to be representative of mortality in 2021 and are excluded from the 2021 reference year counts. These death registrations are presented in the publication in the following outputs: 

• In the year of occurrence data cubes. 
• For the 72 deaths which were due to suicide, these deaths are presented in the time series in the year in which they were registered in both the data cubes and commentary. 
• The Victorian additional registrations are excluded from all other tables and commentary.

8. For most causes, changes in the coded data at the ICD-10 chapter level would have a small impact on the mortality rate and not have any great impact on the time series continuity, at both the Victoria and national level. There are other deaths such as accidental drug overdose and assaults where the proportional increase is higher and consideration should be given as to the impact of the additional registrations on a topic of interest. The table below provides an adjusted time series where the additional death registrations are included in the year in which they were registered. It also shows the percentage increase of each cause of death if the additional registrations were included. 
 

9. Data on suicide from the national mortality dataset is used extensively by government, researchers and non-governmental organisations to inform policy and planning. Time series data looking at changes in these causes of death over time is often used as a measure to understand the impacts of policy including prevention and intervention activities. It is important that the dataset accurately represent patterns of mortality over time in order to be a useful resource for informing these important decisions. For preventable causes of death with high policy impact such as suicide, it is important that information is represented correctly and easily understood by its users. 

10. In acknowledgement of this the ABS has made an adjustment to all statistics presented in this publication for deaths due to suicide. For this cause, the additional death registrations received from the Victorian RBDM for 2013 to 2016 have been included in their respective registration years for all outputs in this publication. This adjustment creates a more accurate time series for the 2013 to 2016 reference period for this cause of death. The table below shows the unadjusted and adjusted time series for deaths due to suicide for Victoria and Australia.
 

Customised tables based on the data available in this publication is available through a paid data consultancy. Provide details through a Consultancy Request Form to find out more information. Access to a cause of death unit record file with data compiled and coded using ICD-10 is available for research purposes to eligible agencies. Applications for access can be made through the Australian Coordinating Registry. 

1. Deaths that are referred to a coroner can take time to be fully investigated. To account for this, the ABS implemented a revisions process for those deaths where coronial investigations remained open at the time preliminary cause of death codes were assigned. Typically, the revisions process is commenced 12 and 24 months after data is first published. Data are deemed preliminary when first published, revised when published the following year and final when published after a second year.

2. The revisions process has been applied to all reference periods from 2006 onwards. Revisions are one of two measures implemented to enable timely data to be released on coroner certified deaths (see 'Revisions process' under the Data quality section of methodology for further information). The second measure, referred to as 'open coding', ensures that all available documentation is considered when assigning a cause of death to coronial cases that are yet to be finalised. The combination of these two measures, along with ongoing enhancements in the timeliness and completeness of documentation available on the National Coronial Information System (NCIS), have resulted in significant improvements to the quality of preliminary Causes of Death data. 

3. There are key improvements to Causes of Death data gained through the revisions process: 

• For deaths from natural causes a more specified condition may be identified. For example, a death may have a preliminary code of unspecified heart disease (I51.9), but with the later addition of an autopsy report, coronary artery disease (I25.1) is identified with the updated code applied through the revisions process.
• For deaths from external causes (accidents, assaults and suicides) more information might be provided on mechanism. For example, a death coded to an unspecified accident with a fracture of hip, may later be updated to report the injury as being caused by a fall down steps.
• External causes may also have the intent of death updated through revisions. For example, a drug-induced death where the intent of death was not determined at preliminary coding, may be updated to an intentional drug-induced death (i.e., suicide) when a coronial finding has been made.
• Injury and poisoning information may be updated. For example, at preliminary coding a drug-induced death may not yet have the specific drugs contributing to death documented. While the death will be counted as drug-induced in nature, the drug code will remain unspecified (T509, unspecified drugs, medicaments and biological substances). The death may later be found to be a mixed drug toxicity with heroin, benzodiazepine and alcohol involvement.
• Deaths caused by Accidental drug poisoning (X40-X44), Intentional self-harm by mechanism of drug poisoning (X60-X64) and Sudden Infant Death Syndrome (SIDS) (R95) are particularly sensitive to the revisions process. Deaths from these causes require intensive investigations to accurately determine the cause and manner in which the death occurred. Therefore, some key reports may not be available on the NCIS when preliminary coding of these deaths occurs. As investigations progress and reports are uploaded to the NCIS, more detailed information regarding the context of the death can be captured.
• Associated cause and risk factor information may also be added as part of the revisions process. For  example, a death may be coded as due to suicide. At the completion of a coronial investigation further information may be made available regarding personal circumstances of the deceased including presence of chronic disease, mental health conditions and drug and alcohol use. Since 2017, psychosocial risk factors (e.g. financial issues, relationship issues) relating to the deceased have been coded alongside other co-morbidities. These factors may also be added to a death record as part of the revisions process.

4. Included in the scope of revisions for a given reference period are:

• Deaths referred to the coroner where the investigation remains open,
• Coroner certified deaths where the investigation has closed since the last revisions cycle,
• Coroner certified deaths where additional information has been added to the NCIS since last coded, and
• Doctor certified deaths where updated or corrected cause of death information has been supplied to and processed by the ABS.

5. For further information regarding the scope of cause of death statistics, see Data collection in the methodology section of this publication. 

6. Various improvements to the availability and timeliness of national mortality information have been undertaken over several years. One major improvement is the more timely upload of reports and information for open coroner cases to the NCIS. This information can then be used at an earlier point by the ABS to improve the quality of open coding for deaths referred to the coroner. Earlier availability of reports can reduce the number of deaths from Ill-defined causes of mortality (R99) and Event of undetermined intent (Y10-Y34) present in the dataset at preliminary coding.

7. Until the 2014 processing cycle, the ABS released the annual Causes of Death dataset 15 months after the end of each reference period (i.e. data for the 2014 reference period was published in March 2016). Causes of Death, Australia, 2015 was released 6 months earlier, representing a significant change in processing of the national mortality dataset. The improved timeliness in report attachment on the NCIS was a key factor in enabling the ABS to bring forward the publication of annual causes of death data.

8. Bringing forward the release of Causes of Death data meant that preliminary coding of coroner certified deaths occurred approximately 6 months earlier than in previous years. As the timeliness of report availability on the NCIS is critical to the ABS's ability to assign specific cause of death codes, considerable analysis was undertaken to ensure the preliminary dataset would be of sufficient quality to be fit for purpose. See Technical Note 1 A More Timely Annual Collection: Changes to ABS Processes in the 2015 publication.

9. The earlier release of data resulted in a higher number of deaths assigned to Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99) at preliminary coding. Subsequently, since the change to the revisions process in 2015, there has been a larger proportional decrease in deaths coded to R00-R99 after the first round of revisions coding has occurred. The table below shows the proportional change at the ICD-10 chapter level by year after the revisions process has been applied.

10. At the time of coding, 2021 data had a higher proportion of open coroner cases than at the time of preliminary coding in previous years.  This is evident in the preliminary 2021 dataset by a higher proportion of deaths due to Other ill-defined and unspecified causes of mortality (R99). To address this, an early targeted revision of 2021 deaths referred to a coroner has been conducted with the aim of assigning more specified causes to three underlying causes that are ill-defined in nature. These codes are Other ill-defined and unspecified causes of mortality (R99), Exposure to unspecified factor (X59) and Unspecified event, undetermined intent (Y34). Data for 2021 is considered to be a preliminarily revised. For further information on the scope and outcomes of this early revision to 2021 data, see Technical note: Causes of death revisions, 2021 preliminary revisions.

1. This technical note focuses specifically on the cause of death revisions process applied to deaths registered in 2019. This is the second revision to this dataset meaning 2019 registration year data is now considered final. The methods and scope of the revisions process are outlined in Technical note: Causes of death revisions methodology in this publication.

Doctor certified deaths

2. An issue was identified with cause of death data for doctor certified deaths registered between 2016-2020 in Western Australia. Information originating from Part II of the Medical Certificate of Cause of death (MCCD) or Medical Certificate of Cause of Perinatal Death (MCCPD) was not uploaded into the ABS Mortality processing system. Consequently, conditions certified in Part II of these records were not assigned an ICD-10 code and were not taken into account when applying mortality coding rules to assign the underlying cause of death. There were 7,110 records affected in 2019. The majority of these records did not have a change in the underlying cause of death, but instead had additional associated causes added. Specific details on these records are included in Technical note: Updates to doctor certified causes of death, Western Australia, 2016-2020 and presented in data cubes 16 and 17 in this publication (accessed via data downloads from the Causes of Death, Australia topic page).

3. An issue was identified with cause of death data for Queensland where information originally provided to the ABS in Part II of the Medical Certificate of Cause of Death (MCCD) was moved to Part I of the MCCD when uploaded into the ABS Mortality processing system. As a consequence, some cause information did not align with the original certificate and the change in sequence altered the application of the ICD-10 coding rules when assigning the underlying cause of death. This impacted 342 (1.1%) Queensland doctor certified records in the 2019 reference year.

After recoding, key changes for these records were: 

• 132 were reassigned to a different underlying cause of death,
• There was a net increase of 100 associated causes of death, and
• The greatest impact on underlying cause was for deaths due to diabetes mellitus (E10-E14), which decreased in frequency. The majority of these deaths were reassigned to diseases of the circulatory system (I00-I99).

The cause information for the impacted records has now been recoded and these updates are presented in the final 2019 data in this revisions technical note and data cube 16 in Causes of Death, Australia 2021.

Victorian additional registrations

4. In the 2019 reference period, an additional 2,739 Victorian death registrations from 2017 and 2018 were identified that had not been previously provided to the ABS. Of those additional deaths, 1135 (41.4%) were registered in 2017 and 1604 (58.6%) were registered in 2018. Victorian additional deaths that were registered in 2017 or 2018 and referred to a coroner were in scope for the 2019 revisions process. This included 905 registrations from 2017 and 819 registrations from 2018.

5. A time series adjustment was made to the data cubes attached to this publication, where the additional Victorian registrations for 2017 and 2018 have been placed back in their respective registration years for deaths due to suicide, assault and accidental drug poisoning (see Technical note: Victorian additional registrations and time series adjustment in the Causes of Death, Australia, 2019 Methodology for more information).

6. In the technical notes in this publication, all additional Victorian registrations are presented in their respective registration years to maintain consistency of time series and enable more meaningful comparisons. Therefore, data presented in technical notes (redistributed for all causes of death) may differ from that presented in the attached data downloads (redistributed for deaths due to suicide, assault and accidental drug poisoning only).

7. Further information on specific coding changes to the Victorian additional registrations through the revisions process are discussed in paragraphs 28 – 30 of this technical note.

Coroner referred deaths

8. Most changes during a revisions process occur to deaths that were referred to a coroner. This is due to updates and changes to information and reports available to the ABS as the coronial investigation progresses. The remainder of this technical note will focus on changes to coroner referred deaths.

9. Table 1 provides the counts of coroner certified deaths by ICD-10 chapter for the 2019 reference period across the revisions process. Revisions are most likely to result in decreases in the number of deaths assigned to Symptoms and signs (R00-R99) with corresponding increases in other chapters.

10. Deaths which are originally coded to the Symptoms and signs (R00-R99) chapter can be reassigned to specific natural or external causes of death. In 2019, over three quarters of those reassigned from R00-R99 were found to be deaths from natural causes, with Diseases of the circulatory system (I00-I99) being the most common natural cause chapter for deaths to be reassigned to.

Of those reassigned from Symptoms and signs (R00-R99) chapter to external causes of death: 

• 65 were found to be accidental drug-induced deaths (X40-X44),
• 34 were deaths due to accidents with a specified mechanism (V00-X39, X45-X58), and
• 5 were deaths due to intentional self-harm (suicide) (X60-X84, Y87.0).

11. There were also 220 records that were updated from being coroner certified to doctor certified across the 2019 revisions cycle. When a death occurs, it may be referred to a coroner for investigation. During this time the death record may be sent to the ABS and be flagged as a coronial death. At a later point in the process the death may be deemed as non-reportable, and a doctor completes a medical certificate of cause of death. The ABS may not be informed immediately of the change, meaning the certifier type may be updated at a later time and incorporated as part of the revisions process. As a result, the total number of coroner certified deaths may differ from preliminary to revised and revised to final data.

12. The purpose of the revisions process is to improve data quality. Enhancements to the quality of underlying cause data may include improvements to either mechanism or intent or identifying an underlying cause where not previously possible. While the revisions process has some impact on statistical output at the chapter level of the ICD-10 (particularly for R00-R99), data improvements become more apparent when considering movements within individual chapters.

13. Table 2 shows data for coroner certified deaths only at the sub-chapter level. There were key data improvements for specification of mechanism for external causes of deaths over the 2019 revisions period. There were 222 deaths where intent was specified at preliminary coding but the mechanism of death was unknown. This decreased by 148 deaths (66.7%) through the revisions process. The majority of these 148 records did not change intent. For example, a death due to suicide where the mechanism was unspecified at preliminary coding (Intentional self-harm by unspecified means (X84)) may be revised to a suicidal drowning (Intentional self-harm by drowning (X71)) as an autopsy becomes available for analysis.

14. Cases assigned to Ill-defined and unspecified causes of mortality (R99) decreased by 41.0% over the full 2019 revisions process (preliminary to final).

15. Table 3 provides information on changes at the sub-chapter level for the 2019 reference period, with a focus on the External causes of morbidity and mortality (V01-Y98) chapter. Deaths due to external causes often require more extensive investigations to accurately determine the cause, manner, and intent of the death, and can be subject to greater change across revisions cycles. As investigations are finalised, more information generally becomes available on the NCIS and coders may use this information to further specify or update causes of death.

16. Notable increases in deaths due to external causes over the full revisions process include: 

• Accidental drug-induced deaths (X40-X44) increased by 103 deaths.
• Accidental falls increased by 40 deaths.
• Intentional self-harm (X60-X84, Y87.0) increased by 58 deaths. The majority of these 58 deaths were originally assigned to an event of undetermined intent (Y10-Y34).
• Car occupant injured in transport accident (V40-V49) increased by 28 deaths. Most of these deaths were reassigned from Unspecified vehicle accident (V89) and Crashing of motor vehicle, undetermined intent (Y32).

Drug-induced deaths

17. Over the revisions process there was a net increase of 109 coroner certified drug-induced deaths (includes all intents: Accidental (X40-X44), Intentional (X60-X64), Assault (X85) and Undetermined (Y10-Y14)). Accidental drug-induced deaths (X40-X44) accounted for 76.3% of the increase.

18. There are multiple complex factors which need to be considered when a death is certified as drug-induced. The timing between the death and toxicology testing can influence the levels and types of drugs detected, making it difficult to determine the true level of a drug at the time of death. Individual tolerance levels may also vary considerably depending on multiple factors, including sex, body mass and a person’s previous exposure to a drug. Contextual factors around the death must also be considered such as pre-existing natural disease and reports from informants (e.g., friends and families) regarding the circumstances surrounding death. For these reasons, the certification of a death as being drug-induced can take significant time to complete, making these deaths particularly sensitive to the revisions process.

19. There were 139 records that were reassigned as Accidental drug-induced deaths (X40-X44) over the revisions period. Of these: 

• 65 (46.8%) were initially coded to Other ill-defined and unspecified causes of mortality (R99). These deaths typically had only a police report available at preliminary coding, where circumstances surrounding death can be unclear and often present similarly to deaths from natural causes.
• 25.2% were initially coded to a drug-induced death of undetermined intent (Y10-Y14).

20. There were 56 records that were reassigned as Intentional (i.e. suicide) drug-induced deaths (X60-X64). Of these:

• 32.1% were initially coded as death due to suicide with a mechanism other than drug poisoning. With additional reports available the mechanism of death was updated.  
• A quarter were initially coded to a drug-induced death of undetermined intent (Y10-Y34).

21. Coronial investigations can also result in changes to the intent of death as well as type of drug identified for deaths that were already established as drug-induced during preliminary coding.

• Over half (50.2%) of the records changed within the drug-induced death category during the 2019 revisions reference period were already established as drug-induced at preliminary coding. These deaths had an update to the either the intent of death or drug type contributing to death.
• Accidental drug-induced deaths (X40-X44) most frequently had an update to the drug type during the revisions process. Over half of those updated changed from a single drug overdose to a multi-drug overdose.
• For drug-induced deaths of undermined intent (Y10-Y14) that had an underlying cause change, 94.2% were reassigned to a drug-induced death of a different intent type (67.3% to accidental 26.9% to intentional self-harm). The majority of these retained the same drug types assigned during preliminary coding. For example, an opioid-induced death of undetermined intent may have changed to an accidental opioid-induced death.

22. The revisions process has traditionally focused on improving specificity of the underlying cause of death. Timeliness of NCIS report attachment means preliminary underlying cause coding has improved over time, with fewer changes to underlying causes between revision iterations. As a result, the majority of changes that occur in the revisions process are additions to the associated cause dataset. Associated causes include the type of injuries sustained by a deceased person, drug type in a drug-induced death (e.g., heroin, cannabis), chronic disease (e.g., cancer), mental and behavioural disorders (e.g., depression, anxiety) and psychosocial risk factors. Associated cause statistics are used extensively in policy formulation. Revisions to associated causes typically focus on enhancements for three key areas - drug specification in drug-induced deaths, mental and behavioural disorders, and psychosocial risk factors implicated in deaths from external causes.

Associated causes for drug-induced deaths

23. Policies directed at reducing drug-induced deaths employ a variety of strategies which can be dependant on drug type. Information regarding the type of drug(s) in a drug-induced death can be reliant on the availability of an autopsy, toxicology or coronial finding report. When these reports are not available, the drug type may be unknown to the ABS and coded to Other and unspecified drugs, medicaments and biological substances (Unspecified drug) (T50.9). Importantly, deaths coded with an Unspecified drug (T509) are still counted as a drug-induced death at preliminary output, but they may be enhanced with more specific information about drug type via the revisions process.

24. From preliminary to final, the number of drug-induced deaths in 2019 where drug type was not specified (T50.9) decreased from 87 to 7. As a result, there was an increase in the number of specified drug types (see Table 4).  Benzodiazepines (T42.4) recorded the largest increase (124 additional mentions) when analysed by single drug type (four-digit ICD-10 code). This was followed by Other opioids (T40.2) (68 additional mentions) and Psychostimulants with abuse potential (T43.6) (53 additional mentions).

25. Associated causes of death may also provide critical insights into risk factors for drug-induced deaths, and these factors may differ by intent of death. Table 5 shows the most common associated causes of death and psychosocial risk factors (excluding drug types), added to accidental drug-induced deaths over the revisions process. Of note:

• Chronic substance use disorders were identified in an additional 122 accidental drug-induced deaths over the revisions process.
• Mood disorders (F30-F39) were identified in an additional 79 deaths.
• Problems related to legal circumstance (Z65.0-Z65.4) was the most commonly mentioned psychosocial risk factor associated with accidental drug-induced deaths, and increased by 45 mentions from preliminary to final.

Associated causes for intentional self-harm (suicide)

26. Associated causes of death can provide important contextual information for deaths due to Intentional self-harm (X60-X84, Y87.0). At preliminary coding, 87.6% of suicides had associated causes (including chronic conditions and psychosocial risk factors) mentioned in coronial investigation documentation on the NCIS. Through the revisions process, this proportion increased to 92.9%. Table 6 shows the most common associated causes of death added over the revisions process as they relate to Intentional self-harm (X60-X84, Y87.0).

27. Notable changes in associated causes for deaths due to intentional self-harm across the 2019 revisions process include the following:

• Suicide ideation (R45.8) had the greatest increase in frequency through revisions, identified in an additional 176 deaths.
• Mood disorders (F30-F39) were the most common associated cause overall for deaths due to suicide, identified in an additional 174 deaths.
• Problems in relationships (Z63.0, Z63.5) (which refers to spousal relationship issues including conflict and separation), was the most common psychosocial risk factor in deaths due to suicide, and were identified in an additional 120 deaths over the revisions period.
• Chronic substance use disorders were identified in an additional 107 deaths.

28. Of the 1,724 coroner referred deaths that were registered in Victoria between 2017 and 2018 and lodged with the ABS in the 2019 reference year, the underlying cause of death changed for 43 records. A further 36 records had associated causes added with no change to the underlying cause.

29. For those registered in 2017:

• 21 records were reassigned to a different underlying cause during the revisions process.
• 11 were reassigned from one natural cause to another.
• One death was reassigned from an event of undetermined intent to intentional self-harm. This change is considered in scope for redistribution in data cubes (i.e., coded to an underlying cause of intentional self-harm, accidental drug poisoning, or assault).

30. For those registered in 2018:

• 22 records were reassigned to a different underlying cause during the revisions process.
• 10 were reassigned from one natural cause to another.
• Two deaths were reassigned from accident to assault, bringing them into scope for redistribution in data cubes. There was no change to mechanism for these deaths. 
• One death was reassigned from intentional self-harm to a natural cause, removing it from scope for redistribution in data cubes (i.e., no longer coded to an underlying cause of intentional self-harm, accidental drug poisoning, or assault).

1. This technical note focuses specifically on the revisions process applied to deaths registered in 2020. This is the first revision to this dataset meaning 2020 registration year data is now considered revised. The methods and scope of the revisions process are outlined in Technical note: Causes of death revisions methodology in this publication.

Doctor certified deaths

2. An issue was identified with cause of death data for doctor certified deaths registered between 2016-2020 in Western Australia. Information originating from Part II of the Medical Certificate of Cause of death (MCCD) or Medical Certificate of Cause of Perinatal Death (MCCPD) was not uploaded into the ABS Mortality processing system. Consequently, conditions certified in Part II of these records were not assigned an ICD-10 code and were not taken into account when applying mortality coding rules to assign the underlying cause of death. There were 6,966 records affected in 2020. The majority of these records did not have a change in the underlying cause of death, but instead had additional associated causes added. Specific details on these records are included in Technical note: Updates to doctor certified causes of death, Western Australia, 2016-2020 and presented in data cubes 16 and 17 in this publication (accessed via data downloads from the Causes of Death, Australia topic page).

3. An issue was identified with cause of death data for Queensland where information originally provided to the ABS in Part II of the Medical Certificate of Cause of Death (MCCD) was moved to Part I of the MCCD when uploaded into the ABS Mortality processing system. As a consequence, some cause information did not align with the original certificate and the change in sequence altered the application of the ICD-10 coding rules when assigning the underlying cause of death. This impacted 306 (1.0%) Queensland doctor certified records in the 2020 reference year.

After recoding, key changes for these records were:

• 107 were reassigned to a different underlying cause of death,
• There was a net increase of 92 associated causes of death, and
• The greatest impact on underlying cause was for deaths due to diabetes mellitus (E10-E14), which decreased in frequency. The majority of these deaths were reassigned to diseases of the circulatory system (I00-I99).

The cause information for the impacted records has now been recoded and these updates are presented in the revised 2020 data in this revisions technical note and data cube 16 in Causes of Death, Australia 2021.

4. In 2022 the ABS received updates to the causes of death for some doctor certified neonatal deaths registered in New South Wales in 2020. These updates meant that neonatal deaths with an unspecified cause of death (P969) were able to be assigned to a more specified underlying cause. These updates are presented in this technical note and data cube 16 in this publication.

Coroner referred deaths

5. Most changes during a revisions process occur to deaths that were referred to a coroner. This is due to updates and changes to information and reports available to the ABS as the coronial investigation progresses. The remainder of this technical note will focus on changes to coroner referred deaths.

6. Table 1 provides the counts of coroner certified deaths by ICD-10 chapter for the 2020 reference period from preliminary to revised. Revisions are most likely to result in decreases in the number of deaths assigned to Symptoms and signs (R00-R99) with corresponding increases in other chapters.

7. Deaths which are originally coded to the Symptoms and signs (R00-R99) chapter can be reassigned to specific natural or external causes of death. In 2020 the majority of those reassigned from R00-R99 were subsequently found to be deaths from natural causes (70.5%), with Diseases of the circulatory system (I00-I99) being the most common natural cause chapter for deaths to be reassigned to.

Of those reassigned to external causes of death:

• 85 were found to be accidental drug-induced deaths (X40-X44),
• 62 were deaths due to accidents with a specified mechanism (V00-X39, X45-X58), and
• 15 were deaths due to Intentional self-harm (suicide) (X60-X84, Y87.0).

8. There were also 133 records that were updated from being coroner certified to doctor certified in 2020. When a death occurs, it may be referred to a coroner for investigation. During this time the death record may be sent to the ABS and be flagged as a coronial death. At a later point in the process the death may be deemed as non-reportable, and a doctor completes a medical certificate of cause of death. The ABS may not be informed immediately of the change, meaning the certifier type may be updated at a later time and incorporated as part of the revisions process. As a result, the total number of coroner certified deaths may differ from preliminary to revised and revised to final data.

9. The purpose of the revisions process is to improve data quality. Enhancements to the quality of underlying cause data may include improvements to either mechanism or intent or identifying an underlying cause where not previously possible. While the revisions process has some impact on statistical output at the chapter level of the ICD-10 (particularly for R00-R99), data improvements become more apparent when considering movements within individual chapters.

10. Table 2 shows data for coroner certified deaths only at the sub-chapter level. There were key data improvements for specification of mechanism for external causes of deaths over the over the 2020 revisions period. There were 171 deaths where intent was specified at preliminary coding but the mechanism of death was unknown. This decreased by 101 deaths (59.1%) through the revisions process.  The majority of these 101 records did not change intent. For example, a death due to suicide where the mechanism was unspecified at preliminary coding (Intentional self-harm by unspecified means (X84)) may be revised to a suicidal drowning (Intentional self-harm by drowning (X71)) as an autopsy becomes available for analysis.

11. For deaths certified by a coroner, cases assigned to Ill-defined and unspecified causes of mortality (R99) decreased by 32.7% over the first revision period (preliminary to revised).

12. Table 3 provides information on changes at the sub-chapter level for the 2020 reference period, with a focus on the External causes of morbidity and mortality (V01-Y98) chapter. Deaths due to external causes often require more extensive investigations to accurately determine the cause, manner, and intent of the death, and can be subject to greater change across revisions cycles. As investigations are finalised, more information generally becomes available on the NCIS and coders may use this information to further specify or update causes of death.

13. Over the first revisions the number of deaths due to external causes increased by 225 deaths. Changes during the first revision period include:

• Accidental drug-induced deaths increased by 111 deaths (X40-X44).
• Accidental falls increased by 47 deaths.
• Intentional self-harm (X60-X84, Y870) increased by 57 deaths. The majority of these 57 deaths were originally assigned to an event of undetermined intent (Y10-Y34).
• Deaths with an undetermined intent decreased by 93. Generally a more specific intent was able to be assigned with the availability of more information in coronial reports.

Drug-induced deaths

14. From preliminary to revised there was a net increase of 103 coroner certified drug-induced deaths (includes all intents: Accidental (X40-X44), Intentional (X60-X64), Assault (X85) and Undetermined (Y10-Y14)). Accidental drug-induced deaths (X40-X44) contributed the largest increase across intent types for 2020, accounting for 77.6% of the increase.

15. There are multiple complex factors which need to be considered when a death is certified as drug-induced. The timing between the death and toxicology testing can influence the levels and types of drugs detected, making it difficult to determine the true level of a drug at the time of death. Individual tolerance levels may also vary considerably depending on multiple factors, including sex, body mass and a person’s previous exposure to a drug. Contextual factors around the death must also be considered such as pre-existing natural disease and reports from informants (e.g., friends and families) regarding the circumstances surrounding death. For these reasons, the certification of a death as being drug-induced can take significant time to complete, making these deaths particularly sensitive to the revisions process.

16. There were 138 records which were reassigned to Accidental drug-induced deaths (X40-X44) over the first revision. Of these:

• 61.6% were initially coded to Other ill-defined and unspecified causes of mortality (R99). These deaths typically had only a police report available at preliminary coding, where circumstances surrounding death can be unclear and often present similarly to deaths from natural causes.
• 26.8% were initially coded to a drug-induced death of undetermined intent (Y10-Y14).

17. There were 46 records that were reassigned to Intentional (i.e. suicide) drug-induced deaths (X60-X64). Of these:

• 34.8% deaths were initially coded as accidental drug-induced deaths (X40-X44). These deaths often only have police reports available on NCIS at the time of preliminary coding where the intent of death may still be unclear to investigators.
• A further 28.3% were initially coded to a drug-induced death of undetermined intent (Y10-Y34).
• 13.0% were initially coded as death due to suicide with a mechanism other than drug poisoning. As additional reports became available the mechanism of death was updated.

18. The revisions process has traditionally focused on improving specificity of the underlying cause of death. Timeliness of NCIS report attachment means preliminary underlying cause coding has improved over time, with fewer changes to underlying causes between revision iterations. As a result, the majority of changes that occur in the revisions process are additions to the associated cause dataset. Associated causes include the type of injuries sustained by a deceased person, drug type in a drug-induced death (e.g., heroin, cannabis), chronic disease (e.g., cancer), mental and behavioural disorders (e.g., depression, anxiety) and psychosocial risk factors. Associated cause statistics are used extensively in policy formulation. Revisions to associated causes typically focus on enhancements for three key areas - drug specification in drug-induced deaths, mental and behavioural disorders and psychosocial risk factors implicated in deaths from external causes.

Associated causes for drug-induced deaths

19. Policies directed at reducing drug-induced deaths employ a variety of strategies which can be dependant on drug type. Information regarding the type of drug(s) in a drug-induced death can often depend on the availability of an autopsy, toxicology or coronial finding report. When these reports are not available, the drug type may be unknown to the ABS and coded to Other and unspecified drugs, medicaments and biological substances (Unspecified drug) (T50.9). Importantly, deaths coded with an Unspecified drug (T50.9) are still counted as a drug-induced death at preliminary output, but they may be enhanced with more specific information about drug type via the revisions process.

20. From preliminary to revised, the number of drug-induced deaths in 2020 where drug type was not specified (T50.9) decreased from 89 to 11. As a result, there was an increase in the number of specified drug types (see Table 4). Benzodiazepines (T42.4) recorded the largest increase (112 additional mentions) when analysed by single drug type (four-digit ICD-10 code). This was followed by Other opioids (T40.2) (71 additional mentions) and Psychostimulants with abuse potential (T43.6) (63 additional mentions).

21. Associated causes of death may also provide critical insights into risk factors for drug-induced deaths, and these factors may differ by intent of death. Table 5 shows the most common associated causes of death and psychosocial risk factors (excluding drug types), added to accidental drug-induced deaths over the first revisions. Of note:

• Chronic substance use disorders were identified in an additional 133 accidental drug-induced deaths.
• Mood disorders (F30-F39) were identified in an additional 91 deaths.
• There were an additional 79 accidental drug-induced deaths where anxiety and stress-related disorders (Z73.3, F40-F48 excl. F41.8, F45.4) were identified.
• Problems related to legal circumstance (Z65.0-Z65.4) was the most commonly mentioned psychosocial risk factor associated with accidental drug-induced deaths, and increased by 44 mentions from preliminary to revised.

Associated causes for intentional self-harm (suicide)

22. Associated causes of death and psychosocial risk factors can provide important contextual information for deaths due to Intentional self-harm (X60-X84, Y870). At preliminary coding, 89.2% of suicides in 2020 had associated causes (including chronic conditions and psychosocial risk factors) mentioned in coronial investigation documentation on the NCIS. Over the first revision, this proportion increased to 93.8%. Table 6 shows the most common associated causes of death added over the revisions process as they relate to Intentional self-harm (X60-X84, Y87.0).

23. For deaths due to suicide, mental and behavioural disorders (F00-F99) and Psychosocial risk factors (Z00-Z99) were commonly added as additional contextual information over the first revision period. 

24. Notable updates for associated causes and risk factors added for deaths due to intentional self-harm over the first revision period in 2020 were:

• Mood disorders (F30-F39), including depression and bipolar affective disorder, were identified in an additional 125 deaths.
• Suicide ideation (R45.8) and personal history of self-harm (Z91.5) were identified in an additional 115 and 84 deaths respectively.
• An additional 78 deaths identified anxiety and stress-related disorders (Z73.3, F40-F48 excl. F41.8, F45.4).
• Problems in relationships (Z63.0, Z63.5), (which refers to spousal relationship issues including conflict and separation), were identified in an additional 74 deaths.

1. Typically, coroner referred death data are revised 12 months and 24 months after data are first published. The ABS revisions process was implemented to update cause of death data for deaths that had open coronial investigations or limited information available at preliminary coding. Data is considered preliminary when first published, revised when published the following year and final when published after a second year. 

2. Following a usual revisions cycle, this would mean that coronial cases for 2021 would be first reviewed in early 2024. At the time of coding the preliminary 2021 data there was a higher proportion of open coroner cases than compared to previous years (67.2% in 2021 versus a 5-year average for 2015-2019 of 56.2%). This is evident in the preliminary 2021 dataset by a higher proportion of deaths due to Other ill-defined and unspecified causes of mortality (R99). Cases coded to R99 made up 9.8% of the coroner referred deaths dataset in 2021, compared with a historical average of 6.3% for preliminary data. Of the 2021 coroner referred cases, 74.6% are open cases that fall within the scope of the ABS causes of death revisions process.

3. In consideration of this, an early targeted revision of 2021 coroner certified deaths was conducted for three causes that are ill-defined in nature. The aim was to assign more specified causes of death and reduce the number of deaths coded to ill-defined causes. The targeted causes of death were:

• Other ill-defined and unspecified causes of mortality (R99) (all information is unknown about the cause of death),
• Exposure to unspecified factor (X59) (the mechanism of death is unknown), and
• Unspecified event, undetermined intent (Y34) (both the intent and mechanism of death is unknown)

4. Data for 2021 is considered a preliminary revision. The full revisions process for 2021 data will be applied from early 2024 with further updates likely.

5. Included in the scope of revisions are 2021 coroner certified reference year records that were coded to one of the three causes R99, X59 or Y34 and that have an open case status or those which have closed since the last revisions cycle.

6. Also included are Queensland records where formatting issues affected coding for 2021 doctor certified reference year records. In 2022 an issue was identified with cause of death data for Queensland whereby information originally provided to the ABS in Part II of the Medical Certificate of Cause of Death (MCCD) was moved to Part I of the MCCD when uploaded into the ABS Mortality processing system. As a consequence, some cause information did not align with the original certificate and the change in sequence altered the application of the ICD-10 coding rules when assigning the underlying cause of death. This impacted 607 records for the 2021 reference year representing 1.9% of doctor certified deaths in Queensland.

The cause information for the impacted records has now been recoded and these updates are presented in the revised 2021 data in this revisions technical note and cube 16 in Causes of Death, Australia 2021.

7. Records in the 2021 reference year include:

• Deaths registered in, and received by the ABS, in 2021,
• Deaths registered in 2021 and received by the ABS in the first quarter of 2022, and
• Deaths registered in the years prior to 2021 but not received by ABS until 2021 or the first quarter of 2022, provided that these records have not been included in any statistics from earlier periods.

For further information surrounding scope of cause of death statistics, see Scope and coverage in the Methodology section of this publication.

8. The purpose of the revisions process is to improve data quality. As the 2021 process is targeted at the revisions of the three specified codes that are ill-defined in nature, the aim was to assign a more specified underlying cause of death. Enhancements to underlying cause data quality may include improved understanding of either mechanism or intent or identifying an underlying cause where not previously possible.

9. Table 1 below shows updated data for coroner certified deaths only for the three targeted causes of death (R99, X59 and Y34). Of deaths in scope for the 2021 revisions period, 498 were able to be assigned to more specific causes of death.

• The number of deaths assigned to ill-defined and unspecified causes of mortality (R99) decreased by 419 (20.4%). The preliminary revision reduced the total proportion of coroner certified deaths coded to R99 to 7.8% (down from 9.8%). This more closely aligns the 2021 dataset with historical averages of preliminary data coded to R99.
• There were 167 deaths coded to accidental intent where the mechanism was unspecified (X59). Through the preliminary revision, deaths coded to X59 had a net decrease of 60 (35.9%).
• There were 40 deaths coded where both the intent and the mechanism was unspecified (Y34). Through the preliminary revision, deaths coded to Y34 had a net decrease of 19 (47.5%).

10. Table 2 shows the changes to the 419 records that were initially coded to Other ill-defined and unspecified causes of mortality (R99) for the 2021 reference period.

11. Close to two-thirds of deaths (63.0%) reassigned from R99 were due to natural causes. Of these 264 deaths: 

• There were 148 records reassigned as Diseases of the circulatory system (I00-I99). Ischaemic heart diseases comprised the majority of these (60.8%).
• There were 30 records reassigned as Endocrine, nutritional and metabolic diseases (E00-E90), of which half were deaths due to Diabetes mellitus (E10-E14).

12. The remaining 155 deaths were reassigned to external causes. Of these deaths:

• The majority were reassigned to Accidents (122) with 76 reassigned to Accidental poisoning by drugs and alcohol (X40-X49).
• There were 15 records reassigned to Intentional self-harm (suicide) (X60-X84, Y87.0).

13. There were 63 deaths coded to Accidental exposure to unspecified factor (X59) that were able to be reassigned as part of the preliminary revision. Table 3 shows the reassignment of these 63 deaths. 

14. The majority (93.7%) of these deaths remained as external causes (V01-Y98). Of these 59 deaths:

• There were 56 that remained as accidents with updates to the mechanism (V01-X58). Of these, 34 were reassigned to falls and 13 to transport accidents.
• There were 2 reassigned to Intentional self-harm (X60-X84, Y87.0).
• There was 1 reassigned to Event of undetermined intent (Y10-Y34).

15. There were 20 deaths coded to Unspecified event, undetermined intent (Y34) that were able to be reassigned as part of the preliminary revision. Table 4 shows the reassignment of these 20 deaths. 

16. The majority (95.0%) of these records remained classified as deaths due to external causes (V01- Y98). Of these 19 deaths:

• There were 12 reassigned to Accidents (V01-X59), half of which were falls.
• There were 5 reassigned to Intentional self-harm (suicide) (X60-X84, Y87.0).
• There were 2 with updates to mechanism only, with the intent remaining as undetermined (Y10-Y33).

1. As part of the ABS's revisions process for Causes of Death, the ABS updates causes for coroner certified deaths at 12 and 24 months after initial publishing, to reflect the latest available information. A final revision has now been applied to 2019 data, a first revision to 2020 data and a preliminary revision to 2021 data. More information regarding these revisions, including the scope and methodology, can be found in relevant Technical notes in this publication.  

2. As coronial investigations regarding deaths due to suspected suicide can be extensive, it is a cause of death which may be more heavily impacted by revisions. It is important from a public health perspective to have accurate counts of suicides. As such, this technical note focusses on how the revisions process has changed the number of deaths due to suicide in 2019, 2020 and 2021.

3. Over time there has been a reduction in the number of deaths that are reassigned to suicide through the revisions process. In 2006 and 2007, the first years for which revisions were applied, the number of deaths due to suicide increased by 17.7% and 18.5%, respectively. In 2019, the final number of suicides is 1.8% higher than the preliminary count. Several factors have impacted on the increased quality of preliminary data, including enhanced coding practices, enabling greater use of documents available on the National Coronial Information System (NCIS) and more timely report attachment.

4. In scope for the revisions process is the updating and inclusion of associated causes of death and risk factors as they relate to suicide. This may include coding of more specified substances (drugs) and risk factors such as mental health conditions, chronic diseases and psychosocial factors as they become available in coronial reports on the NCIS. Technical notes on revisions of 2019 and 2020 data (above) contain detailed information on the addition of these associated causes and risk factors through the revisions process.

5. There were 178 suicides that were registered in Victoria in 2017 (88 suicides) and 2018 (90 suicides) but not supplied to the ABS until 2019. These additional registrations are in scope for the revision of the 2019 reference period and have now been finalised. The final counts for these deaths are published in their corresponding registration years (2017 and 2018) in the tables below to maintain consistency of time series. 

6. The final number of deaths due to suicide recorded for 2019 is 3,377. This is a net increase of 59 suicides (1.8%) from the preliminary count of 3,318. The number of deaths due to suicide increased by 40 over the first revision period and 19 over the second revision period.

7. Deaths which have been reassigned to suicide through the revisions process were most likely to be initially coded to an Event of undetermined intent (Y10-Y34) (56 deaths) or Accidental drug poisoning (X40-X44) (10 deaths). Additionally:

• 7 deaths were initially coded to Exposure to unspecified factor causing other and unspecified injury (X59.9),
• 5 deaths were initially coded to Other ill-defined and unspecified causes of mortality (R99), and
• A small number of deaths had a change in the recorded mechanism of death as additional documentation became available (especially toxicology and pathology reports).

8. The revised number of suicides in 2020 is 3,196. This is a net increase of 57 suicides (1.8%) from the preliminary count of 3,139. Of the deaths reassigned as due to suicide over the first revision:

• 42 were initially coded to Event of undetermined intent (Y10-Y34),
• 16 were initially coded to Accidental drug poisoning (X40-X44), and
• 15 were initially coded to Other ill-defined and unspecified causes of mortality (R99).

9. The preliminary revised number of deaths due to suicide in 2021 is 3,166. This is a net increase of 22 suicides (0.7%) from the preliminary count of 3,144. Of the deaths reassigned to suicide over the preliminary revision:

• 15 were initially coded to Other ill-defined and unspecified causes of mortality (R99),
• 5 deaths initially coded to Event of undetermined intent (Y10-Y34), and
• 2 were initially coded to Exposure to unspecified factor causing other and unspecified injury (X59.9).

10. The 2021 reference year will undergo further updates as part of usual revisions cycles in future. It is anticipated that further improvements and specificity of types of deaths will be captured as part of this process.

11. Table 1 shows the total number of deaths due to suicide for Australia at each stage of the revisions process from 2017 to 2021. Deaths due to suicide in 2017 and 2018 are included in the table as the additional Victorian registrations provided to the ABS in 2019 are in scope as part of the 2019 reference year revisions cycle.

12. The 2017 and 2018 registration years show the greatest number and percent increase from preliminary to final. This is due to 178 additional Victorian death records being supplied to the ABS in 2019 that were registered over 2017 and 2018. See Data collection: Historical considerations, Victorian additional registrations in the methodology of this publication for further information.

13. The number and age-standardised death rate of deaths due to suicide (intentional self-harm) by state and territory and sex from 2012 to 2021 are shown in Tables 2 - 7. These tables provide an updated time series that includes the revisions for 2019, 2020 and 2021. The data presented in these tables should now be used in preference to those published in October 2022. A more detailed table which includes revised suicide counts by mechanism (ICD-10 codes X60-X84 and Y87.0) are provided in the Revisions data cube 16 in the Downloads tab of this publication. Further tabulations are available on request. Please contact the National Information and Referral Service on 1300 135 070.

1. An issue was identified with cause of death data for doctor certified deaths registered between 2016-2020 in Western Australia. Information originating from Part II of the Medical Certificate of Cause of death (MCCD) or Medical Certificate of Cause of Perinatal Death (MCCPD) was not uploaded into the ABS Mortality processing system. Consequently, conditions certified in Part II of these records were not assigned an ICD-10 code and were not taken into account when applying mortality coding rules to assign the underlying cause of death. Coding of coroner certified deaths was not impacted as cause of death information for these deaths is obtained from the National Coronial Information System. 

2. Part II of the MCCD is used to record any other significant conditions contributing to the death but not related to the disease or condition causing it (i.e. the underlying cause of death listed on the lowest line in Part I). Consequently the main impact of not having Part II information when coding a certificate is on the associated causes - both in terms of the capture of conditions listed and the number of causes listed as contributing to death. There was a change to the underlying cause of death for just over 10% of affected records. 

3. The affected registrations have now been recoded to include the Part II information on the MCCD originally certified by the doctor. Table 1 presents a summary of the issue. Of all doctor certified deaths registered in Western Australia between 2016 to 2020: 

• Over half had associated causes added, 
• On average, 1.212 causes per death record were added, and
• 13.4% of affected records had a change in the underlying cause of death.

4. Associated causes of death include all conditions on the MCCD except for the underlying cause (the disease or external event causing the train of morbid conditions leading to death). Associated causes of death are valuable in recognising the impact of conditions and diseases which are less likely to be an underlying cause as well as highlighting relationships between diseases listed on the death certificate. With an ageing population and a greater propensity for people to die with multiple co-morbidities contributing to death, the value of associated cause data has increased in recent years. 

5. As discussed in paragraph 2, the MCCD has two parts. Part I lists all conditions involved in the morbid train of events that lead to death. Part II lists other significant conditions that contributed to the death but were not related to the condition causing death. For doctor certified deaths, Part II most often includes co-morbidities that are chronic conditions (for example, diabetes, coronary heart disease or dementia). During mortality coding, Part II conditions are typically assigned as associated causes after mortality coding rules are applied.

6. Table 2 shows the number of associated causes mentioned by ICD-10 chapter before and after records were recoded to include Part II from the MCCD for each reference year. The ICD-10 chapter most impacted by this issue was Diseases of the circulatory system (I00-I99). For this chapter the associated cause mentions increased by approximately 5,000 for each year over the five years. It is not uncommon for multiple circulatory diseases to be certified on one MCCD. For example, a person may have had hypertension, a previous stroke and generalised atherosclerosis listed as significant factors contributing to death listed in Part II of the MCCD. In this example, associated cause circulatory disease mentions would be recorded as 3.   

7. At the 3-digit level, Essential (primary) hypertension (I10), Type 2 diabetes mellitus without complications (E11.9) and Unspecified atrial fibrillation and atrial flutter (I48.9) were the most commonly added associated causes.

8. Table 3 shows the average number of ICD-10 cause of death codes listed on the MCCD before and after recoding the affected records for each reference year. For all doctor certified death registrations in Western Australia between 2016 and 2020, the average number of conditions listed on the MCCD increased from 2.439 to 3.651. On average, 1.212 causes were added after recoding.

9. All entries on the MCCD are taken into account when assigning the underlying cause of death. While the underlying cause of death is most often selected from Part I, it can sometimes be selected from a condition certified in Part II depending on the quality of certification and the application of the mortality coding rules. The underlying cause of death changed for 13.4% of all doctor certified records registered in Western Australia between 2016 and 2020 when information from Part II was taken into account. The most common change was for an ill-defined condition to be assigned to a more specific underlying cause of death. A number of records that were initially coded to an acute condition such as Pneumonia (J18) were able to be coded to an underlying chronic condition such as Dementia (F01, F03, G30) or Chronic lower respiratory diseases (J40-J47).

10. Table 4 shows the underlying cause of death by ICD-10 chapter before and after recoding affected records to include Part II for each reference year. At the chapter level, the most common change was a decrease in Diseases of the respiratory system (J00-J99), with a corresponding in increase in Mental and behavioural disorders (F00-F99) (specifically dementia F01, F03).