Anticholinergic medications and risk of community-acquired pneumonia in elderly adults: a population-based case-control study.

OBJECTIVES: To determine whether use of anticholinergics is associated with risk of community-acquired pneumonia in older adults.
DESIGN: Population-based case-control study.
SETTING: An integrated healthcare delivery system in Washington State. PARTICIPANTS: Data from a nested case-control study of community-dwelling immunocompetent adults aged 65 to 94 were analyzed. Pneumonia cases (n=1,039) were ascertained according to International Classification of Diseases, Ninth Revision, codes from 2000 to 2003 and validated using chart review. Controls (n=2,022) were matched 2:1 to cases according to age, sex, and year. MEASUREMENTS: Anticholinergic medication exposure was ascertained using prescription data; acute use was defined as one or more prescription fills 90 days or less before the index date (date of pneumonia diagnosis), past use was defined as one or more prescription fills within the prior year but none within 90 days, and chronic use was defined as three or more prescription fills within the prior year. The reference group was those with no fills in the prior year. Conditional logistic regression was used to analyze the association between anticholinergic use and pneumonia, adjusted for comorbidities.
RESULTS: Acute use of anticholinergics was observed in 59% of cases and 35% of controls (adjusted odds ratio (aOR)=2.55, 95% confidence interval (CI)=2.08-3.13) and past use in 17% of cases and 23% of controls (aOR=1.19, 95% CI=0.92-1.53). Chronic use of anticholinergics was observed in 53% of cases and 36% of controls (aOR 2.07, 95% CI=1.68-2.54). Results were not different for high- and low-potency anticholinergic medications.
CONCLUSION: In older adults, anticholinergic medication use is associated with pneumonia risk, adding to substantial evidence suggesting that these medications are high risk.