Appropriateness of antibiotic use for individuals >65 years of age: A population-wide analysis

Objective To assess the appropriateness of outpatient antibiotic prescribing over a 24-year period. Methods We conducted a population-based retrospective cohort study using linked health administrative databases from 2000 to 2023 in Ontario, Canada. Oral antibiotic dispensations from the Ontario Drug Benefit Program were linked to physician billing claims. The study population included all adults aged >65 years. Prescription indication appropriateness was based on diagnostic codes from the clinician billings and categorized as Tier 1 (always), Tier 2 (sometimes), or Tier 3 (never appropriate). Proportional odds regression models, with random intercepts for physicians, were used to identify patient and prescriber characteristics associated with inappropriate antibiotic use for the year 2023. Results Between 2000 and 2023, overall antibiotic prescribing rates declined from 64 to 44 prescriptions per 100 person-years. The proportion of prescriptions classified as Tier 3 (never appropriate) also decreased, from 46.7% in 2000 to 37.3% in 2023. For Tier 1 conditions, antibiotic prescriptions increased from 10.6% to 13.1%, and for Tier 2, they increased from 13.9% to 21.4%. In 2023, multivariable regression models identified migrant status, male patient sex, younger patient age, physician male sex, international vs. Canadian medical degree, 25+ vs. <11 years since graduation, and median daily visits as independent predictors associated with less appropriate antibiotic prescribing. Conclusions We identified improvements in antibiotic prescribing among older adults in Ontario; however, substantial inappropriate prescribing persists. These findings can help set targets and priorities for antimicrobial stewardship interventions to improve outpatient prescribing quality and address disparities in care.