A decade of outpatient antimicrobial use in older adults in Ontario: a descriptive study.

BACKGROUND: Antimicrobials are frequently prescribed to community-dwelling older adults. Our aim was to examine the prevalence, quantity and indications of antimicrobial prescriptions to older residents of Ontario.

METHODS: We conducted a population-based analysis of outpatient antimicrobial prescriptions to residents of Ontario aged 65 years or more from 2006 to 2015. Antimicrobial prescriptions, infectious disease diagnoses and prescriber information were determined from linked health care databases. Our analyses were primarily focused on antibiotics, which account for most antimicrobial use.

RESULTS: We identified 2 879 779 unique Ontario residents aged 65 years or more over our study period. On average, 40.7% (range 40.1%-41.5%) of older adult outpatients in any given year received 1 or more antibiotic prescriptions. Antibiotic use remained stable over the study period, averaging 25.1 (range 24.1-25.6) defined daily doses per 1000 person-days per year. Selection of antibiotics evolved, with increasing use of penicillins and decreasing use of fluoroquinolones and macrolides. For 65.7% of prescriptions, no infectious disease diagnoses were identified within 7 days of the prescription. Among prescriptions with an associated diagnosis, upper respiratory tract infection was most common (18.9%), followed by urinary tract infection (6.2%), skin/soft-tissue infection (4.3%), lower respiratory tract infection (4.2%) and other infection (1.2%). Most antibiotics were prescribed by family physicians.

INTERPRETATION: Antibiotic use among older adult outpatients in Ontario remained stable between 2006 and 2015. Current methods of measuring use are not capable of accurately determining indication, and, thus, additional data sources to monitor the appropriateness of community antimicrobial use are needed.