Socio-demographic and health service factors associated with antibiotic dispensing in older Australian adults

Abstract

Background: Widespread use of antibiotics has led to the development of antibiotic resistance. However, there are limited data describing antibiotic use in the community setting, and examining factors associated with greater use. Our study aimed to quantify antibiotic dispensing in older adults in the community according to socio-demographics and health services use.

Methods: Prospective analysis of a population-based cohort study of 239,981 adults aged ≥45 years in Australia (the Sax Institute's 45 and Up Study). Data on socio-demographics and health from a questionnaire, were linked to 2015 antibiotic dispensing data from the Pharmaceutical Benefits Scheme (PBS), as well as other administrative health databases. We estimated the Defined Daily Dose (DDD) of systemic antibiotics dispensed, defined by an Anatomic Therapeutic Classification code beginning with J01, in 2015. We also conducted Poisson regression with robust standard errors to identify factors associated with antibiotic dispensing.

Results: Overall, 49.3% of 45 and Up Study participants had at least one systemic antibiotic dispensed in 2015 with a total of 392,856 prescriptions dispensed and an average of 36.5 DDDs/1000-persons/day in the study population. The quantity of antibiotics dispensed increased with increasing age (25.6 DDDs/1000/day in <60 years old versus 50.4 DDDs/1000/day in 80+ year old) and was higher comparing women to men (39.9 versus 32.4 DDDs/1000/day). Of factors examined, the greatest dispensing of antibiotics was among those who had been resident in an aged care facility and those with >15 general practitioner consultations in the last year (80.5 and 88.3 DDDs/1000/day, respectively). These factors remained strongly associated with greater antibiotic dispensing after adjusting for age, sex, education, income, area of residence and co-morbidities.

Conclusions: Residence in aged care facilities and high GP visits are associated with greater antibiotic dispensing. This study provides important evidence regarding high use groups for antimicrobial stewardship.

Fig 1. Distribution of antibiotic dispensing by age and sex in 2015.

Fig 2

Mean DDD of systemic antibiotics dispensed per 1000 persons per day according to number of GP consultations and age (A), residence in aged care in the last year (B) and hospitalisations in last year (C).