Abstract
INTRODUCTION: Administrative datasets can be used to calculate population incidence and prevalence of dementia. It is unclear how changes in data sources may affect these estimates. METHODS: We obtained linked administrative health data for individuals 60 years of age or older in Western Australia for 1989-2019 (n = 893,243) including hospital admissions, emergency department, cause-of-death, aged care assessment (from April 2003), and mental health services. RESULTS: There was a marked increase in prevalence and incidence estimates over time. There appeared to be two phases: an initial increase attenuated by 1995-1999 and a rapid increase since 2000-2004 corresponding to inclusion of aged care assessments. There was a decrease in 2015-2019 coinciding with the unavailability of aged care assessment data. DISCUSSION: An apparent secular change in rates of dementia over 31 years may be a product of increased propensity to record dementia diagnosis and availability of additional aged care data. Consistent comprehensive data coverage is required.