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OVERVIEW

Mortality analysis primarily focuses on underlying causes of death. The underlying cause is the disease or condition which led directly to the death. These underlying causes are coded in accordance with the International Classification of Diseases – Version 10 (ICD-10). However, death certificates contain more information than just the underlying cause of death. The certificates also include significant diseases and/or conditions which led to or contributed to death (i.e. associated causes). Multiple cause of death statistics refer to both underlying and associated causes of death (see Causes of Death, Australia (cat. no. 3303.0) Glossary for further details). Multiple cause of death data have been compiled for Australia since 1997.

Across the causes of death dataset, multiple cause data is particularly valuable in providing an insight into deaths which can be attributed to a number of concurrent disease processes. It enables the identification of patterns of association amongst conditions, links which may assist in targeting health interventions. This chapter focusses on multiple cause data for suicide deaths.

From the outset, it is important to distinguish between the number of times a cause or group of causes appears on death records and the number of deaths where the cause (or group of causes) is mentioned. For example, if a death record contained three different codes from the range of codes belonging to Diseases of the circulatory system (I00-I99), then there are three causes (within the circulatory disease chapter), but only one death. Counts presented in this chapter reflect the number of suicide deaths where a particular multiple cause has been identified. Where more than one multiple cause has been identified for a particular death it may contribute to counts against more than one condition or group of conditions, but it will only contribute once to the total number of deaths. Care needs to be taken when analysing multiple cause of death data associated with suicide deaths.

DATA QUALITY

Data quality depends on the procedures being followed at every stage of collection and processing of statistical information. The quality of multiple cause of death data is particularly dependent on the contribution that doctors and coroners make when recording information about a death. When analysing multiple causes of death data, it is important to note that some conditions present at death will not be identified, effectively leading to under-reporting of associated causes and conditions. The extent to which under-reporting of multiple causes of death occurs is unknown and there may be differences in the likelihood of particular conditions being identified.

Most suicide deaths are sudden or unexpected in nature. This, combined with a low median age at death, means that the likelihood of associated conditions being identified and recorded is also low. However, in some cases, mental health conditions, cancers or other terminal conditions may be viewed as a trigger or precursor to the suicide event. A secondary cause of death was recorded for only 22% of deaths from suicide between 2001 and 2010 compared to 96% for all deaths during the same period.

The data presented in this chapter focuses only on the 22% of suicide deaths from 2001-2010 for which an associated cause was recorded. Care should be taken in making inferences about all suicide deaths based on this sub-group.

SUICIDE DEATHS WITH MULTIPLE CAUSES

Between 2001 and 2010, 22,526 deaths were registered where suicide was determined to be the underlying cause. Of these suicide deaths, 22% (4,932) were recorded with a multiple cause of death; that is, any condition, disease or injury which was involved in the morbid train of events leading to death (see Glossary for further details). This chapter focuses on data for these 4,932 suicide deaths with multiple causes recorded.

Table 7.1 reports the number of suicide deaths by multiple cause by 10 year age groups. For instance, in Table 7.1, there were 340 suicide deaths of 15-24 year olds where the group of multiple causes Mental and behavioural disorders (F00-F99) was listed. The sub-categories of Mental and behavioural disorders (F00-F99) also include counts of suicide deaths. One death may be counted in more than one sub-category but can only contribute once at the broader level of the classification. Consequently, counts of suicide deaths at the sub-category level will add up to more than the total for this group of causes.

Table 7.2 reports selected multiple causes as a proportion of only those suicide deaths for which a multiple cause was recorded.

The likelihood of a multiple cause of death being identified with a suicide increases with age. Only 19.6% of 15-24 year olds who died of suicide had a multiple cause identified, while this increased to 31.4% for individuals aged 75 years or older. It should be noted that this trend may reflect the tendency for a greater number of medical conditions to be present in advanced age.

A Mental or behavioural disorder (F00-F99) was recorded for over half of all individuals who died from suicide and for whom a multiple cause was identified. The highest incidence of these disorders was observed in younger age groups: 58.6% of persons aged between 15 and 24 years and 61.6% of persons aged between 25 and 34 years. A Mental and behavioural disorder (F00-F99) was listed as a multiple causes for only 23.0% of individuals aged 75 years and over who died from suicide and for whom a multiple cause was identified.

Within the category Mental and behavioural disorders (F00-F99), two disorders were most commonly associated with suicide: Mood disorders (F30-F39) and Mental and behavioural disorders due to psychoactive substance use (F10-F19). These disorders were also the most common Mental and behavioural disorders recorded with suicide across all age groups. Mood disorders (F30-39) were reported in 28.1% of all suicides where a multiple cause was identified, and occurred most often in suicides of 45-54 year olds (33.4%). Mental and behavioural disorders due to psychoactive substance use were recorded in 19.4% of all suicides where a multiple cause was identified, and were most prevalent for persons aged between 15 and 24 years and 25 and 34 years (30.0 and 30.2% of these age groups respectively).

The prevalence of the main associated causes of death at the ICD-10 chapter level, for those suicide deaths where a multiple cause was identified, is shown in Figure 7.1.

Amongst all deaths where suicide was found to be the underlying cause, only 22% had an associated (multiple) cause of death, whereas for all underlying causes of death, 96% had associated causes. There were differences observed between the types of multiple causes of death associated with suicide and the multiple causes observed when all other underlying causes were considered. Table 7.3 presents the proportions of deaths with selected multiple causes for all underlying causes of death.

For deaths due to any underlying cause, Diseases of the circulatory system (I00-I99, associated with 59.7% of deaths), Neoplasms (C00-D48, 35.0%) and Diseases of the respiratory system (J00-J99, 31.8%) were the most common diseases or conditions that contributed to death. Suicide deaths were most commonly associated with Mental and behavioural disorders (F00-F99, 50.2%), Diseases of the circulatory system (I00-I99, 19.4%), and Diseases of the respiratory system (J00-J99, 9.6%).