A comparative analysis of the prevalence of medicine classes and polypharmacy between community‐dwelling and residential aged care populations in Western Australia

Abstract Background Polypharmacy is a global issue, particularly among residential aged care home (RACH) residents with multimorbidity and complex care needs. However, population‐level evidence on longitudinal trends and comparisons with community‐dwelling (CD) older adults remains limited. Aim To compare the prevalence, trends and factors associated with polypharmacy among adults aged >65 years in Western Australia (WA), Australia, between CD and RACH populations. Method Linked national and state administrative data were analysed to assess cumulative polypharmacy, defined as the total number of unique medicine classes dispensed over a three‐month window (October–December) each Australian financial year (1 July–30 June) from 2012–2013 to 2018–2019. Individuals were grouped into five categories: 0, 1, 2–4, 5–8, and 9+ medicine classes. Frequently dispensed medicine classes were identified. Multinomial logistic regression examined trends and associations with demographic and clinical characteristics. Ethics approval was granted by the Curtin University Human Research Ethics Committee (Reference no: RD‐42‐14), Department of Health Western Australia Human Research Ethics Committee (Reference no: RGS0000002902), and the Australian Institute of Health and Welfare Ethics Committee (Reference no: EO2020/2/1138 ID 2533) and the study conforms to the Australian National statement on ethical conduct in human research . A waiver of consent, which approved study access to deidentified linked administrative health data, was granted because: the study involved secondary analysis of routinely collected, population‐level data; obtaining consent from all included individuals was deemed impracticable; and the research posed minimal risk to participants. Results In the 2018–2019 financial year, 346 786 older adults were included. CD adults most commonly used 2–4 medicine classes (36%), whereas RACH residents most commonly used 5–8 medicine classes (36%). Common medicine classes included renin–angiotensin–aldosterone system inhibitors, statins, proton pump inhibitors, beta‐blockers, and opioids. Opioid use was higher among RACH residents, while biguanides and non‐steroidal anti‐inflammatory medicines were more common among CD adults. Higher multimorbidity, socio‐economic disadvantage, and metropolitan residency were associated with higher medicine use. Conclusion Polypharmacy is highly prevalent among older adults in WA, particularly in residential aged care. Differences between CD and RACH populations highlight opportunities to improve polypharmacy monitoring, guide deprescribing, and medicine use policies.