Notes on the data: ABORIGINAL AND TORRES STRAIT ISLANDER SELF-ASSESSED HEALTH
Self-assessed health, estimated Aboriginal population aged 15 years and over, 2018–19
Policy context: Self-assessed health status is commonly used as a proxy measure of actual health status; and how people rate their health is strongly related to their experience of illness and disability [1,2]. This measure is therefore an important indicator of key aspects of quality of life . However, it has long been known that cultural factors can affect reporting of self-assessed health status. Data for the Aboriginal and Torres Strait Islander population can be similarly impacted. The Australian Institute of Health and Welfare note that many Indigenous Australians rate their health as good or excellent despite significant health problems, which may reflect differences in the social and cultural constructs of health . The data at the state and territory level, when compared with the responses for the whole population in the 2017–18 National Health Survey, show Aboriginal and Torres Strait Islander people in the Northern Territory and New South Wales to have the highest rates of reporting their health as excellent or very good: they are also the jurisdictions with the smallest gap in reporting this item when viewed by Indigenous status.
In 2018–19, 44.5% of Aboriginal and Torres Strait Islander people aged 15 years and over reported their health as excellent or very good, 31.5% reported their health as good and 23.9% rated their health as fair or poor .
- Australian Bureau of Statistics (ABS). Profiles of health, Australia, 2011–13. (ABS Cat. no. 4338.0). Canberra: ABS; 2013.
- Doiron D, Fiebig DG, Johar M, Suziedelyte A. Does self-assessed health measure health? Sydney, NSW: UTS; 2014.
- McCallum J, Shadbolt B, Wang D. Self-rated health and survival: a seven-year follow-up study of Australian elderly. Am J Public Health. 1994;84(7):1100-5.
- Australian Institute of health and Welfare (AIHW). Available from https://www.indigenoushpf.gov.au/measures/1-17-perceived-health-status; last accessed 16 May 2022.
- PHIDU (www.phidu.torrens.edu.au), based on direct estimates from the 2018–19 National Aboriginal and Torres Strait Islander Health Survey, ABS TableBuilder.
Modelled Estimates: Overview
National surveys like the 2018–19 National Aboriginal and Torres Strait Islander Health Survey (NATSIHS) are designed to measure population characteristics for Australia or for a large proportion of the Australian population such as for a state or territory. Due to sample size limitations, it is not possible to provide accurate measures of population characteristics at lower geographic levels. The survey sample size is often too small, resulting in high margins of error. To meet user demands for information at lower geographic levels, the Australian Bureau of Statistics (ABS) can produce modelled estimates. Modelled estimates use both the survey responses for NATSIHS, together with other information about the population of a geographic area gained from the Population Census and administrative data sources to build a predictive model that estimates a given characteristic for a small area. The term “small area” refers to a geographical area that is smaller than a state or territory, such as Indigenous Areas, Indigenous Regions and Primary Health Networks. Strictly speaking modelled estimates are not as reliable as directly estimated survey measures from the NATSIHS. Measures of error are provided with these estimates (in the data) and the Technical Appendix explains what types of error are present.
Modelled estimates can be used for observing national trends by using the complete set of modelled data for IAREs across Australia or a state/territory to support program evaluation or resource allocation or looking at trends across a range of IAREs. For example, looking at a range of areas in remote Australia or along the Eastern seaboard with high or low number or proportion of people with the selected characteristic. A modelled estimate for a single area on its own should be used with extreme caution. Models are limited by the input data. Often significant local information about particular small areas exists but has not been collected for all areas and cannot be incorporated into the models.
The ABS has used a number of methods to measure the quality of the estimates, one of which is the relative root mean squared error (RRMSE) of the modelled estimates. The RRMSEs are included with the data. Users are advised that:
- estimates with RRMSEs less than 25% are considered reliable for most purposes;
- estimates with RRMSEs from 0.25 and to 0.50 have been marked (~) to indicate that they should be used with caution; and
- those greater than 0.50 but less than 1 are marked (~~) to indicate that the estimate is considered too unreliable for general use.
Modelled Estimates: Indigenous Areas and Indigenous Regions
Small area modelled estimates are produced by the ABS to provide users reliable estimates at a lower geographic level than State or Territory. Initially, the ABS produced a set of estimates from the 2018–19 NATSIHS for Indigenous Regions. PHIDU raised the possibility of having similar estimates for a selection of the variables at the (smaller) Indigenous Area level, for Indigenous Areas where the population was large enough and the particular variable had a sufficiently high proportion in the population. The ABS agreed, and it is the result of their further work that is presented here.
Where estimates could not be made for an Indigenous Area, as a result of its population size, the data for that Indigenous Area have been grouped with other, unpublished Indigenous Areas within the over-arching Indigenous Region, and a rate for the combined group calculated and published. Modelled estimates use both the survey responses from the NATSIHS, together with other information about the population of a geographic area gained from the Population Census and administrative data sources to build a predictive model that estimates a given characteristic for a small area. Details of the method used and accuracy of results are available from the ABS Explanatory Notes: Modelled estimates for small areas based on the 2018–19 National Aboriginal and Torres Strait Islander Health Survey
For the Indigenous Regions of Tasmania (IREG601) and Australian Capital Territory (IREG801), direct estimates were published instead of modelled estimates. Estimates for States and Territories, Greater Capital City Statistical Areas (GCCSA) and Remoteness Areas are also direct estimates, extracted using the ABS TableBuilder.
The data on which the estimates are based are self-reported data, reported to interviewers in the NATSIHS. Respondents aged 15 years and over were asked to assess their health on a scale from 'poor' to 'excellent' (the scale was 'poor', 'fair', 'good', 'very good', or 'excellent'). Data reported are the sum of responses categorised as 'poor or fair', 'good' and 'very good or excellent'.
Geography: Data available by Indigenous Area (including Indigenous Region) and Remoteness Area
Numerator: Estimated number of Aboriginal people aged 15 years and over with fair or poor/good/excellent or very good self-assessed health
Denominator: Aboriginal population aged 15 years and over
Detail of analysis: Indirectly age-standardised rate per 100 population (aged 15 years and over); and/or indirectly age-standardised ratio, based on the Australian standard
Indigenous Areas: Age-standardised rates are based on Australian Bureau of Statistics data, produced for PHIDU, from the 2018–19 National Aboriginal and Torres Strait Islander Health Survey.
Indigenous Regions: Age-standardised rates are based on Australian Bureau of Statistics data from the 2018–19 National Aboriginal and Torres Strait Islander Health Survey: Small Area Estimates, Australia (ABS Cat. no. 4715.0).
Remoteness Areas: Compiled by PHIDU based on direct estimates from the 2018–19 National Aboriginal and Torres Strait Islander Health Survey, ABS TableBuilder.