Antibiotic use in older Australians with and without dementia in primary care

Antibiotics are commonly prescribed in older community-dwelling adults, contributing to adverse effects, antimicrobial resistance and increased healthcare costs. Prescribing patterns in dementia are unclear, although healthcare use and goals of care change around diagnosis.

To describe trends in antibiotic dispensing and prevalence amongst Australians aged ≥70 years, compare dispensing between those with and without dementia and identify factors associated with dispensing.

We analysed data from 13 659 ASPREE and ASPREE-XT participants (2010-20). Antibiotic dispensing was assessed using Pharmaceutical Benefits Scheme records, with rates stratified by age group. Interrupted time-series analysis compared dispensing rates and the proportion of broad- versus narrow-spectrum antibiotics dementia case and matched controls (matched on time since randomisation, age and sex). Negative binomial regression identified factors associated with dispensing.

Dispensing rates increased to 1651 per 1000 person-years (95% CI: 1604-99) by year 9. Annual prevalence averaged 47%. Broad-spectrum antibiotics were dispensed twice as often as narrow-spectrum. Individuals with dementia had higher dispensing both before and after diagnosis, but dementia was not independently associated with dispensing (IRR 1.06, 95% CI: 0.95-1.18). Female sex, polypharmacy, pre-frailty and higher depressive symptom scores were linked to higher dispensing, whilst hypertension, dyslipidaemia and alcohol use were linked to lower dispensing.

Antibiotic dispensing in older adults remains high, dominated by broad-spectrum agents. Dementia was not independently associated with increased dispensing. Female sex, polypharmacy, pre-frailty and depressive symptoms identified groups who may benefit most from targeted antimicrobial stewardship interventions.