Identifying people living with dementia in linked data

The exact number of people living with dementia in Australia is currently not known. However, the AIHW has estimated that 401,300 Australians were living with dementia in 2022 (AIHW 2023a). Although it is not possible to identify everyone with dementia in currently available data sources, linked data can bring together information from a range of sources to improve our ability to understand service use among people living with dementia.

The National Integrated Health Services Information (NIHSI) is a multi-source, enduring linked data asset that contains de-identified health care, residential aged care and mortality data from 2010–11 to 2020–21 (AIHW NIHSI 2020–21).

In this study, the dementia study cohort refers to 158,730 people aged 30 and over who were living in Australia in 2019 and had a dementia record in the linked data.

A person was identified as having dementia if they had at least one of the following in the NIHSI:

  • a dementia-specific medication dispensed through the Pharmaceutical Benefits Scheme (PBS)/Repatriation PBS between 2010–11 and 2018
  • a diagnosis of dementia in an emergency department (ED) presentation or public hospital admission (including a supplementary chronic condition code) between 2010–11 and 2018
  • a record of dementia in an Aged Care Funding Instrument (ACFI) assessment between 2010–11 and 2018, and/or
  • dementia recorded as an underlying or additional cause of death between January 2020 and December 2021.

Find out more about how the dementia study cohort was created in the Technical guide.

See Box 1.1 for a discussion on how the study cohort differs from the total population of people living with dementia.

Box 1.1. The dementia study cohort is a subset of people living with dementia

The dementia study cohort comprises 158,730 people aged 30 and over who were living in Australia in 2019 and had a dementia record in the NIHSI. This cohort is a subset of people living with dementia and does not account for all people living with dementia in Australia.  

The exact number of people living with dementia in Australia (the ‘prevalence’) is currently not known and estimates vary widely (Dobson et al. 2023). The AIHW dementia prevalence estimates are derived from a variety of data sources of varying quality, including small-scale Australian and international epidemiological studies. It is not currently known how dementia prevalence rates vary between geographic areas in Australia.

The dementia study cohort only includes people with a record of dementia in one of the administrative data sets in the NIHSI (such as data on medications dispensed, public hospital admissions, residential aged care assessments and causes of death). Hospital data are an important source of dementia information, so to ensure comparability of findings across regions, people from states/territories without hospital data in the linked data (Western Australia and the Northern Territory) were excluded from the cohort. Similarly, as private hospital admissions data were incomplete, the cohort only included people with a public hospital admission for dementia. See the Technical guide for more details on the data available in the NIHSI.

Most administrative data sources for dementia relate to later stages of disease, such as hospital stays, residential aged care and death. Older people with comorbidities are therefore more likely to be identified in the study cohort, while younger people and people in the early to moderate stages of dementia are less likely to be identified. People living in rural and remote areas are also less likely to be identified in the linked data, as they often access specialised aged care services (AIHW 2023b) for which data are not available in the NIHSI (such as the Multi-Purpose Services Program and the National Aboriginal and Torres Strait Islander Flexible Aged Care Program). It should also be noted that dementia is often underreported on death records (AIHW 2023a; Xu et al. 2022).

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