Limitations of the sources of Aboriginal and Torres Strait Islander health information

To assess the health status of Aboriginal and Torres Strait Islander people, it is necessary to have accurate information about both the size of the Aboriginal and Torres Strait Islander population (the denominator for the calculation of rates) and the number of occurrences of particular health conditions and vital events (the numerators for calculating rates). Although the accuracy of both types of information have improved in recent years, limitations exist.

Population

The ABS produces estimates of the resident Aboriginal and Torres Strait Islander population following each census [46281]. These estimates are commonly used as the denominator for the calculation of rates of disease and mortality among Aboriginal and Torres Strait Islander people.

The ABS has made considerable efforts to achieve accurate counts of the Aboriginal and Torres Strait Islander population in the five-yearly Australian censuses [45577]. Despite these efforts, there are impacts on data quality such as non-responses for identification.

As at 30 June 2021, 88% of Aboriginal and Torres Strait Islander Australians were reported to be living in NSW, Qld, WA, SA and the NT (Derived from [46281]) and the data from these jurisdictions are considered of sufficient quality for reporting on many health conditions and vital events such as deaths [44306][47845].

The number of people who identified as Aboriginal and/or Torres Strait Islander increased by 25% between the 2016 and 2021 Censuses [48283]. Less than half this increase is explained by demographic factors such as births between censuses; the rest is explained by non-demographic factors including changes in the way that people identify. Because estimates of the life expectancy of Aboriginal and Torres Strait Islander people are based on data from the census, there is a risk that improvements in life expectancy over time may be attributed to improvements in health rather than to changes in identification [48273][43904].

Health data and vital statistics

A key concern about the various collections of health and vital statistics is that Aboriginal and Torres Strait Islander people are not always correctly identified. There is currently no national approach on how to determine Aboriginal and/or Torres Strait Islander status where classification is inconsistent or missing across multiple data sets, which may lead to different methodologies being applied and difficulties in the interpretability and comparability of data [37682][37046].

Limitations of some of the specific data collections used in the Overview are outlined below.

Births

Variations in data collection practices and in the propensity of parents to self-identify as Aboriginal and Torres Strait Islander mean that Aboriginal and Torres Strait Islander births may be under-reported [47972]. The accuracy of measures of Aboriginal and Torres Strait Islander fertility may also be affected by lags in birth registrations.

The ABS has estimated that the proportion of Indigenous births identified correctly was 96% in 2002-2006, a significant improvement over the level for previous years [18107]. Completeness of identification varied across the country, with only Vic, Qld, WA, SA and the NT having levels above 90%. All jurisdictions are working towards improving the quality of Indigenous status in perinatal data collections [42101].

Hospitalisations

The level of identification in hospital admissions is variable, but overall it has been estimated that 88% of Aboriginal and Torres Strait Islander patients were correctly identified in Australian public hospital admission records (private hospitals were not included [41516]) in 2011-12 [25105]. It has been suggested that the more accurate number of admissions was approximately 9% higher than recorded [41516]. The accuracy of the identification of Indigenous people varied between states and territories, from 98% in the NT to 58% in the ACT [25105]. The accuracy of identification also varied with remoteness level, from 99% in very remote areas to 77% in major cities. A further limitation is that all hospitalisation data for Tas, the ACT and the NT include only public hospitals [41516].

Deaths

A key concern with mortality data is that not all Aboriginal and Torres Strait Islander deaths are correctly identified in death registrations [47845][37682][47832]. The level of Aboriginal and Torres Strait Islander mortality is therefore likely to be underestimated.

While most Aboriginal and Torres Strait Islander deaths are registered, and while Indigenous identification data is provided for most registered deaths (99% in 2022), some of this identification data is known to be inaccurate [47845]. Estimating the proportions of deaths identified correctly is not simple, so it is difficult to calculate the actual number of Indigenous deaths occurring and the corresponding rates. Mortality analysis is usually restricted to the five jurisdictions where identification levels and numbers of deaths are considered sufficient to support analysis: NSW, Qld, WA, SA and the NT [47845]. The ABS uses estimates of the proportions of registered deaths correctly identified as Indigenous in preparing its life tables, the source of life expectancy figures [47832][48095].

Due to concerns about the mortality rates of Aboriginal and Torres Strait Islander people relative to the total population, there has been ongoing data integration to investigate the quality of the data using health and death records by the ABS and state and territory government departments [37682].

Burden of disease

As burden of disease analysis makes use of Aboriginal and Torres Strait Islander population, mortality and disease/risk factor prevalence data, it is subject to the limitations that characterise these types of data [44827]. For example, the reliability of estimates of fatal burden are affected by the potential under-identification of Indigenous status in death registrations.

The accuracy of estimates of burden are also affected by gaps in national Aboriginal and Torres Strait Islander data collection [44827]. For example, estimates of the burden attributable to chronic obstructive pulmonary disease (COPD) are currently based on a small study from WA because national data do not exist.

Other limitations affecting burden of disease analysis for Aboriginal and Torres Strait Islander people include small numbers in the data, the lack of suitable adjustment factors to correct for under-identification, the inability of the current method of estimating fatal burden to account for multiple causes of death, and unknown levels of Indigenous under-identification in key data collections (such as cancer incidence) [44827].

National surveys

The Overview refers extensively to the results of the 2018-19 National Aboriginal and Torres Strait Islander Health Survey (NATSIHS), as well as to other surveys such as the National Drug Strategy Household Survey (NDSHS).

While some surveys do include the collection of health measurements by trained health professionals (e.g. via hearing or vision checks), most data collected by major surveys is self-reported. Self-reported survey data are open to interpretation; they do provide insight into an individual’s view of their health, but these may not have been diagnosed by a health professional [41757]. Self-reported data can underestimate conditions about which respondents may not be aware (such as high blood pressure) or be reluctant to disclose (such as drug use).

Changes in aspects like survey methodology and levels of reporting in publications can cause difficulties in the analysis and synthesis of information for periods of time (i.e. trend analysis). Survey results are also subject to sampling errors. Major national surveys are generally conducted at long intervals (such as every six years), which means that relevant information is often dated.

Other data collections

Other data collections on which the Overview draws include those related to notifiable diseases, social and emotional wellbeing (SEWB), alcohol and other drugs (AOD), community services, primary health care, potentially preventable hospitalisations, screening programs, health registries and pathology.

The levels of Aboriginal and Torres Strait Islander people’s identification in many of these collections vary in their degree of completeness, which questions the quality and accuracy of the various estimates of health status [37046].

The ABS, the AIHW and state and territory authorities have worked together to improve the accuracy of Indigenous status identification in various collections, including:

• pathology forms
• primary health care data
• AOD treatment services
• mental health services
• community services data collection [25330] (cited in [37682]).

COVID-19 highlighted the poor level of identification on pathology forms used for testing [40439][42007][42745], and work is now being undertaken to improve Indigenous identification on pathology forms used by both public and private laboratories.

Data gaps

There are significant gaps in the national data for important areas of Aboriginal and Torres Strait Islander health. An example is cancer, a leading cause of death among Aboriginal and Torres Strait Islander people. National data on cancer incidence and mortality are not available and Indigenous-specific information about screening is only collected for breast cancer and bowel cancer (both self-reported) and not for cervical cancer [42007][36771][43987][43915]. Other examples of national data gaps include gaps in information on dementia [44827][48286] and on hearing loss and otitis media among children aged 0-6 years [45453].

Other limitations

Time periods for which detailed information is available tend to vary substantially; this means that documents like the Overview need to draw on information from various time periods in attempting to compile a comprehensive picture.

Additionally, special reports related to Aboriginal and Torres Strait Islander health (see the Sources of information section in the Introduction) are often selective rather than comprehensive in their coverage of the various health topics.