Methods: Aboriginal People

Recording of Aboriginality in administrative data collections

Assessing the health of the Aboriginal population is difficult for a range of reasons, including errors in estimating the number of Aboriginal people in administrative health data collected by health services and population data collected by the Australian Bureau of Statistics (ABS). The recording of the Aboriginality of a person using a health service in administrative data collections may be incomplete and variable. Aboriginality may be under-reported in administrative data collections because, for a particular occasion of care, staff may not ask whether a person is or is not Aboriginal or because Aboriginal people may be reluctant or choose not to identify as Aboriginal in some circumstances.

The estimated level of enumeration of Aboriginal people in hospital data (Admitted Patient Data Collection) in NSW has increased from 53% in 2001-02 to 84% in 2017-18 (See Reporting of Aboriginality in hospital data for more detail). Recording and reporting of Aboriginality is usually better for rural and remote regions than for major cities.

Differences in population composition and age standardisation

In NSW, the Aboriginal population is relatively young, with a median age of 24 years (ABS 2022). In 2021 in NSW, 33% of Aboriginal persons were aged between 0 and 14 years, 12% were aged 55 to 74 years old, and 1.7% were 75 years or older. By comparison, 24% of non-Aboriginal persons were below 20 years of age, 26% were 55 to 84 years old, and 2.2% were 85 years or older  (See ABS 2022 https://www.abs.gov.au/articles/australia-aboriginal-and-torres-strait-islander-population-summary for more detail) .

As many health conditions are age-related, age standardisation is a technique that can be used to enhance the comparability of data, such as disease rates, between Aboriginal and non-Aboriginal populations. Age standardisation adjusts for the confounding effects of compositional differences in age structure between the populations or sub-populations being compared (AIHW 2011).

In HealthStats NSW, directly age standardised rates are calculated as described below.

Overall

• For the total population: 5-year age groups and persons aged 100+ years are amalgamated into a single age group.
• For the Aboriginal population: 5-year age groups and persons aged 85+ years are amalgamated into a single age group.

Within sub-state geographies (e.g. Local Health Districts)

• For the total population: 5-year age groups and persons aged 85+ years are amalgamated into a single age group.
• For the Aboriginal population: 10-year age groups are used between 5 and 64 years of age, and persons aged 65+ years are amalgamated into a single age group. 

 Note that comparisons of disease and injury rates between Aboriginal and non-Aboriginal populations can sometimes be limited by the low numbers of older Aboriginal persons. The differences between the age structures of Aboriginal and non-Aboriginal populations may result in situations where rate estimates of rare and chronic diseases are less reliable in the Aboriginal compared with the non-Aboriginal population.

Aboriginal population estimates used in HealthStats NSW

The estimated resident Aboriginal populations for NSW used for direct age standardisation in HealthStats NSW were produced by the ABS and are based on the 2021 Census. The non-Aboriginal populations for comparison are estimated by subtracting Aboriginal population estimates from the estimated total population for NSW. No sub-state population projections or recast estimates are currently available for Aboriginal populations based on the 2021 ABS Census. As such, only a single year of data can be reported on HealthStats NSW for sub-state Aboriginal populations, such as Local Health Districts and Primary Health Networks.