INTRODUCTION

1 This publication presents key indicators from the 2014-15 National Health Survey (NHS), including information on:

• the health status of the population, including long-term health conditions;
• health risk factors such as smoking, Body Mass Index, diet, exercise and alcohol consumption; and
• demographic and socioeconomic characteristics.

2 Information on the use of health services, such as consultations with health practitioners, is scheduled for release in the first quarter of 2016.

3 The 2014-15 NHS was conducted throughout Australia from July 2014 to June 2015. Previous surveys were conducted in 1989-90, 1995, 2001, 2004-05, 2007-08 and 2011-12. Health surveys conducted by the ABS in 1977-78 and 1983, while not part of the NHS series, also collected similar information.

SCOPE OF THE SURVEY

4 The NHS was conducted from a sample of approximately 14,700 private dwellings across Australia.

5 Urban and rural areas in all states and territories were included, while Very Remote areas of Australia and discrete Aboriginal and Torres Strait Islander communities were excluded. These exclusions are unlikely to affect national estimates, and will only have a minor effect on aggregate estimates produced for individual states and territories, excepting the Northern Territory where the population living in Very Remote areas accounts for around 23% of persons.

6 Non-private dwellings such as hotels, motels, hospitals, nursing homes and short-stay caravan parks were excluded from the survey. This may affect estimates of the number of people with some long-term health conditions (for example, conditions which may require periods of hospitalisation).

7 Within each selected dwelling, one adult (18 years and over) and one child (0-17 years) were randomly selected for inclusion in the survey. This sub-sampling within households enabled more information to be collected from each respondent than would have been possible had all usual residents of selected dwellings been included in the survey. For the purposes of the NHS, a household was defined as one or more persons, at least one of whom is aged 18 years and over, usually resident in the same private dwelling.

8 The following groups were excluded from the survey:

• certain diplomatic personnel of overseas governments, customarily excluded from the Census and estimated resident population;
• persons whose usual place of residence was outside Australia;
• members of non-Australian Defence forces (and their dependents) stationed in Australia; and
• visitors to private dwellings.

SAMPLE DESIGN

9 Dwellings were selected at random using a multistage area sample of private dwellings. The initial sample selected for the survey consisted of approximately 21,850 dwellings. This was reduced to a sample of 17,958 after sample loss (for example, households selected in the survey which had no residents in scope of the survey, vacant or derelict buildings, buildings under construction). Of those remaining dwellings, 14,723 (or 82.0%) were fully or adequately responding, yielding a total sample for the survey of 19,259 persons.

	NSW	Vic.	Qld	SA	WA	Tas.	NT	ACT	Aust.
Households approached (after sample loss)	3 246	3 196	2 796	2 224	2 250	1 640	1 131	1 475	17 958
Households in sample	2 499	2 547	2 367	1 916	1 865	1 497	775	1 265	14 723
Response rate (%)	77.0	79.7	84.7	86.2	82.9	91.3	68.5	85.8	82.0
Persons in sample	3 272	3 335	3 081	2 434	2 450	1 918	1 057	1 708	19 259

10 To take account of possible seasonal effects on health characteristics, the sample was spread randomly across the 12-month enumeration period. Analysis of previous health surveys has shown no particular seasonal bias across key estimates.

DATA COLLECTION

11 Trained ABS interviewers conducted personal interviews with selected residents in sampled dwellings. One adult (aged 18 years and over) in each dwelling was selected and interviewed about their own health characteristics as well as information about the household (for example, income of other household members). An adult, nominated by the household, was interviewed about one child in the household. Some children aged 15-17 years may have been personally interviewed with parental consent.

WEIGHTING, BENCHMARKING AND ESTIMATION

12 Weighting is a process of adjusting results from a sample survey to infer results for the in-scope total population. To do this, a weight is allocated to each sample unit; for example, a household or a person. The weight is a value which indicates how many population units are represented by the sample unit.

13 The first step in calculating weights for each person was to assign an initial weight, which was equal to the inverse of the probability of being selected in the survey. For example, if the probability of a person being selected in the survey was 1 in 600, then the person would have an initial weight of 600 (that is, they represent 600 others). An adjustment was then made to these initial weights to account for the time period in which a person was assigned to be enumerated.

14 The weights are calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks', in designated categories of sex by age by area of usual residence. Weights calibrated against population benchmarks in this way compensate for over or under-enumeration of particular categories of persons and ensure that the survey estimates conform to the independently estimated distribution of the population by age, sex and area of usual residence, rather than to the distribution within the sample itself.

15 The NHS was benchmarked to the estimated resident population living in private dwellings in non-Very Remote areas of Australia at 31 December 2014. Excluded from these benchmarks were persons living in discrete Aboriginal and Torres Strait Islander communities. The benchmarks, and hence the estimates from the survey, do not (and are not intended to) match estimates of the total Australian resident population (which include persons living in Very Remote areas or in non-private dwellings, such as hotels) obtained from other sources.

16 Survey estimates of counts of persons are obtained by summing the weights of persons with the characteristic of interest. Estimates of non-person counts (for example, number of health conditions) are obtained by multiplying the characteristic of interest with the weight of the reporting person and aggregating.

RELIABILITY OF ESTIMATES

17 All sample surveys are subject to sampling and non-sampling error.

18 Sampling error is the difference between estimates, derived from a sample of persons, and the value that would have been produced if all persons in scope of the survey had been included. Indications of the level of sampling error are given by the Relative Standard Error (RSE) and 95% Margin of Error (MOE). For more information refer to the Technical Note - Reliability of Estimates.

19 In this publication, estimates with an RSE of 25% to 50% are preceded by an asterisk (e.g. *3.4) to indicate that the estimate has a high level of sampling error relative to the size of the estimate, and should be used with caution. Estimates with an RSE over 50% are indicated by a double asterisk (e.g. **0.6) and are generally considered too unreliable for most purposes.

20 Margins of Error are provided for proportions to assist users in assessing the reliability of these data. The proportion combined with the MOE defines a range which is expected to include the true population value with a given level of confidence. This is known as the confidence interval. This range should be considered by users to inform decisions based on the proportion. Proportions with an MOE of greater than 10 percentage points are preceded by a hash (e.g. #40.1) to indicate the range in which the true population value is expected is relatively wide.

21 Non-sampling error may occur in any data collection, whether it is based on a sample or a full count such as a census. Non-sampling errors occur when survey processes work less effectively than intended. Sources of non-sampling error include non-response, errors in reporting by respondents or in recording of answers by interviewers, and errors in coding and processing data.

22 Non-response occurs when people are unable to or do not cooperate, or cannot be contacted. Non-response can affect the reliability of results and can introduce a bias. The magnitude of any bias depends on the rate of non-response and the extent of the difference between the characteristics of those people who responded to the survey and those who did not.

23 In the 2014-15 NHS, measurements of height, weight and waist circumference were taken of respondents aged 2 years and over, while blood pressure was also measured for adult respondents (aged 18 years and over). While these items had relatively high non-response rates, analysis indicated no bias existed in the non-responding population. Imputation was been used to obtain values for respondents for whom physical measurements were not taken. For more information see Appendix 2: Physical measurements in the 2014-15 National Health Survey.

24 The following methods were adopted to reduce the level and impact of non-response:

• face-to-face interviews with respondents;
• the use of proxy interviews in cases where language difficulties were encountered, noting the interpreter was typically a family member;
• follow-up of respondents if there was initially no response; and
• weighting to population benchmarks to reduce non-response bias.

INTERPRETATION OF RESULTS

25 Care has been taken to ensure that results are as accurate as possible. This includes thorough design and testing of the questionnaire, interviews being conducted by trained ABS Interviewers, and quality control procedures throughout data collection, processing and output. There remain, however, other factors which may have affected the reliability of results, and for which no specific adjustments can be made. The following factors should be considered when interpreting these estimates:

• information recorded in the survey is essentially 'as reported' by respondents, and hence may differ from information available from other sources or collected using different methodology; for example, information about health conditions is self-reported and, while not directly based on a diagnosis by a medical practitioner in the survey, respondents were asked whether they had ever been told by a doctor or nurse that they had a particular health condition. Conditions which have a greater effect on people's wellbeing or lifestyle, or those specifically mentioned in survey questions, are expected in general to have been better reported than others;
• some respondents may have provided responses that they felt were expected, rather than those that accurately reflected their own situation. Every effort has been made to minimise such bias through the development and use of appropriate survey methodology; and
• results from previous surveys indicate a tendency for respondents to under-report consumption of alcohol.

Comparability with previous National Health Surveys

26 Data for 2014-15 are comparable with earlier surveys, with some exceptions:

• estimates of people reporting having a mental and/or behavioural condition are not comparable with earlier years. See Explanatory Notes 27 to 29 for more information;
• 'Back problems (dorsopathies)' have been redefined to include sciatica, disc disorders, back pain/problems not elsewhere classified and curvature of the spine. Data for all years presented in this publication use this definition, while previous publications defined 'Back problems' as including only disc disorders and back pain/problems not elsewhere classified;
• during processing of 2014-15 NHS data, an issue with coding of 'Back pain or back problems' in the 2011-12 NHS was identified in which some responses were incorrectly coded to 'Diseases of the digestive system' and 'Symptoms, signs and conditions not elsewhere classified'; analysis indicates that estimates of 'Back pain/problem, disc disorder' published for 2011-12 were under-reported by approximately 540,000 people, 'Diseases of the digestive system' were over-reported by approximately 250,000 people and 'Symptoms, signs and conditions not elsewhere classified' were over-reported by approximately 280,000 people. Data for 2011-12 for 'Back problems (dorsopathies)' are not comparable to other years. Data for 2014-15 have been correctly coded. ABS are investigating options to address this issue for previous years;
• during processing of 2014-15 NHS data, an issue with coding of 'Gout' and 'Rheumatism' in the 2007-08 and 2011-12 NHS was identified in which a large number of people who reported having these conditions were erroneously allocated a status of 'current and long-term', resulting in over-estimation of prevalence in 2007-08 and 2011-12. In 2007-08 'Gout' was over-reported by approximately 800,000 people and 'Rheumatism' by approximately 290,000 persons, while in 2011-12 'Gout' was over-reported by approximately 280,000 people and 'Rheumatism' by approximately 145,000 people. Data for 2007-08 and 2011-12 for these two conditions are not comparable to other years. Data for 2014-15 have been correctly coded. ABS are investigating options to address this issue for previous years;
• 'Heart, stroke and vascular disease' has been redefined to include persons who reported having ischaemic heart diseases and cerebrovascular diseases that were not current and long-term at the time of interview. Data for 2007-08, 2011-12 and 2014-15 in this publication are presented using this definition, while previously published data excluded these persons;
• In this publication, data on diabetes refers to persons who reported having been told by a doctor or nurse that they had diabetes, irrespective of whether the person considered their diabetes to be current or long-term. This definition was first used for estimates of diabetes in Australian Health Survey: Updated Results, 2011-12 (cat. no. 4364.0.55.003). Estimates of diabetes for all years in this publication are presented using this definition. In earlier publications, persons who had reported having diabetes but that it was not current were not included; and
• in 2014-15, in addition to the existing category 'Stroke (including after effects of stroke)' on the prompt card for circulatory conditions, a new category 'Transient ischaemic attack (TIA, 'mini stroke')' was introduced and coded to 'Other cerebrovascular diseases'. As a result estimates of 'Other cerebrovascular diseases' have increased (from 4,900 people in 2011-12 to 171,200 people in 2014-15) while estimates of 'Stroke' have decreased (from 240,000 people to 172,300 people respectively).

27 In 2014-15 a module specifically dedicated to mental and behavioural conditions was included in the NHS to collect information on cognitive, organic and behavioural conditions. In previous NHS cycles, mental and behavioural conditions were collected in a module that included a wide range of long-term health conditions. The number of persons who reported having a mental and behavioural condition in 2014-15 has increased since the 2011-12 NHS, potentially due to the greater prominence of mental and behavioural conditions in the new module. Data on mental and behavioural conditions for 2014-15 are therefore not comparable with data in previous National Health Surveys.

28 The table below presents numbers and proportions of people with mental and behavioural conditions in 2014-15 and 2011-12 to illustrate the effect of the change in collection methodology. Differences between 2014-15 and 2011-12 should not be interpreted as changes in the prevalence of mental or behavioural conditions.

National Health Survey, 2014-15 Estimate '000 Proportion % Alcohol and drug problems 230.9 1.0 Mood (affective) disorders nnnn Depression/feeling depressed 2 052.2 8.9 nnnn Other mood (affective) disorders 179.5 0.8 nnnn Total mood (affective) disorders 2 137.6 9.3 Anxiety related problems nnnn Anxiety disorders/feeling anxious, nervous or tense 2 207.0 9.6 nnnn Panic disorders/panic attacks 585.7 2.5 nnnn Phobic anxiety disorders 303.6 1.3 nnnn Obsessive-compulsive disorder 267.9 1.2 nnnn Post-traumatic stress disorder 232.3 1.0 nnnn Total anxiety related disorders 2 564.1 11.2 Problems of psychological development 293.8 1.3 Behavioural, cognitive & emotional problems with usual onset in childhood/adolescence 257.1 1.1 Other mental and behavioural problems(b) 260.4 1.1 Symptoms and signs involving cognition, perceptions, emotional state and behaviour 40.3 0.2 Total mental and behavioural problems 4 017.4 17.5 Total population 22 969.0 100.0		National Health Survey, 2011-12 Estimate '000 Proportion % Alcohol and drug problems 152.1 0.7 nnnn nnnn nnnn Mood (affective) disorders 2 143.1 9.7 nnnn nnnn nnnn nnnn nnnn nnnn Anxiety related problems 850.1 3.8 Problems of psychological development 154.1 0.7 Behavioural and emotional problems with usual onset in childhood/adolescence 135.7 0.6 Other mental and behavioural problems(b) 196.0 0.9 Symptoms and signs involving cognition, perceptions, emotional state and behaviour 108.3 0.5 Total mental and behavioural problems 2 996.2 13.6 Total population 22 105.3 100.0
(a) Data for 2014-15 are not comparable to earlier years due to a change in collection methodology. In 2014-15, information on mental health conditions was obtained through a new Mental, Behavioural and Cognitive Conditions module, while in previous years it was collected as part of the Long Term Conditions module. (b) Includes organic mental problems.

29 Estimates of people with mental or behavioural conditions from the NHS will differ from those obtained from a diagnostic tool such as that used in the 2007 National Survey of Mental Health and Wellbeing.

30 When interpreting changes over time or differences between population groups (for example, between males and females), reliability of estimates should be taken into account. All comparisons in this publication were tested for statistical significance at the 95% level of confidence; for more information see Technical Note - Reliability of Estimates.

CLASSIFICATIONS

31 Long-term health conditions reported by respondents in the NHS are presented using a classification originally developed for the 2001 NHS by the Family Medicine Research Centre, University of Sydney, in conjunction with the ABS. The classification is based on the 10th revision of the International Classification of Diseases (ICD) and is used for all years from 2001 to 2014-15.

32 Country of birth is classified to the Standard Australian Classification of Countries (cat. no. 1269.0).

33 Main language spoken at home is classified according to the Australian Standard Classification of Languages (cat. no. 1267.0).

34 Descriptions of data items such as Body Mass Index and the Kessler Psychological Distress Scale (K10) are included in the Glossary to this publication.

CONFIDENTIALITY

35 The Census and Statistics Act, 1905 provides the authority for the ABS to collect statistical information, and requires that statistical output shall not be published or disseminated in a manner that is likely to enable the identification of a particular person or organisation. This requirement means that the ABS must take care and make assurances that any statistical information about individual respondents cannot be derived from published data.

36 To minimise the risk of identifying individuals in aggregate statistics, a technique known as perturbation is used to randomly adjust cell values. Perturbation involves a small random adjustment of the statistics and is considered the most satisfactory technique for avoiding the release of identifiable statistics while maximising the range of information that can be released. These adjustments have a negligible impact on the underlying pattern of the statistics. After perturbation, a given published cell value will be consistent across all tables. However, adding up cell values to derive a total will not necessarily give the same result as published totals.

37 Perturbation has been applied to 2014–15 data. Data from previous NHS presented in this publication have not been perturbed, but have been confidentialised if required using suppression of cells.

ROUNDING

38 Estimates presented in this publication have been rounded.

39 Proportions presented in this publication are based on unrounded estimates. Calculations using rounded estimates may differ from those published.

ACKNOWLEDGEMENTS

40 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of 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.

PRODUCTS AND SERVICES

41 Summary results from the NHS are available in spreadsheet form from the 'Downloads' tab in this release. The statistics presented are only a selection of the information collected.

42 For users who wish to undertake more detailed analysis, a TableBuilder product for the 2014-15 NHS is expected to be available in the first quarter of 2016. TableBuilder is an online tool for creating tables from ABS survey data, where variables can be selected for cross-tabulation. It has been developed to complement the existing suite of ABS microdata products and services including Census TableBuilder and CURFs. Further information about ABS microdata, including conditions of use, is available via the Microdata section on the ABS website.

43 Customised tabulations are available on request. Subject to confidentiality and sampling variability constraints, tabulations can be produced from the survey incorporating data items, populations and geographic areas selected to meet individual requirements.

RELATED PUBLICATIONS

44 Other ABS publications which may be of interest are shown under the 'Related Information' tab of this release.

45 Current publications and other products released by the ABS are listed on the ABS website. The ABS also issues a daily Release Advice on the website which details products to be released in the week ahead.