Chronic respiratory disease should be considered when interpreting indicators of community antimicrobial use in people over 65 years old

Objectives Chronic respiratory diseases (CRD) put patients at increased risk of respiratory infection and antimicrobial use, but surveillance results on community antimicrobial use are generally not adjusted for this risk factor. The objective of this study was to demonstrate the importance of accounting for CRD when interpreting indicators of community antimicrobial use in people over 65 years old, in Québec, Canada. Methods Retrospective cohort study of antimicrobial use according to CRD status in individuals over 65 years old covered by Québec’s public drug insurance plan between 2010 and 2015. Defined daily doses per 1000 person-days (DID) were computed per antimicrobial class and were further stratified according to chronic disease group, fiscal year, gender and age group. Results Antimicrobial use was 2.3 times higher in the CRD group (29.7 DID) compared with the other chronic disease group (13.1 DID) and 3.1 times higher than in the no chronic disease group (9.6 DID). The same gradient was reflected as well in use per antimicrobial class, per age group, per gender, and in time. Antimicrobial use increased throughout the study period and was higher in older age groups and in women. Conclusions Interpretation of results of antimicrobial use surveillance should consider the prevalence of CRD in populations. In order to identify opportunities for adapted interventions targeting inappropriate use, finer analyses are necessary.