| Summary: | Introduction
There is no gold standard method for monitoring dementia incidence in Australia. Routinely collected linked administrative data are increasingly being used to monitor endpoints in observational studies and clinical trials and could benefit dementia research.
Objectives and Approach
This study examines dementia incidence within different Australian administrative datasets and how characteristics vary across datasets for groups detected as having dementia. This was an observational data linkage study based on a prospective cohort of 267,153 people in New South Wales, Australia from the 45 and Up Study. Participants completed a survey in 2006-2009 and dementia was identified using linked pharmaceutical claims (provided by Services Australia), hospitalisations, assessments of aged care eligibility, care needs at entry to residential aged care and death certificates. Data linkage was undertaken by the Centre for Health Record Linkage (CHeReL) and the Australian Institute of Health and Welfare. Age-specific and age-standardised incidence rates, incidence rate ratios and survival from first dementia diagnosis were calculated.
Results
Age-standardised dementia incidence was 16.9 cases per 1000 person years (PY) for people aged 65 years and over. Estimates for those aged 80-89 years were closest to published incidence rates (91% of rates for high-income countries). Relationships with dementia incidence were inconsistent across datasets for characteristics including sex, relative socio-economic disadvantage, support network size, marital status, functional limitations and diabetes. Median survival from first pharmaceutical claim for an anti-dementia medicine was 3.7 years compared to 3.0 years from first aged care eligibility assessment, 2.0 years from a dementia-related hospitalisation and 1.8 years from first residential aged care needs assessment.
Conclusion / Implications
People identified with dementia in different administrative datasets have different characteristics, reflecting the factors that drive interaction with specific services. Bias may be introduced if single data sources are used to identify dementia as an outcome in observational studies.
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