Anticholinergic Medication Use and Risk of Pneumonia in Elderly Adults: A Nested Case-Control Study.

OBJECTIVES: To examine the risk of community-acquired pneumonia (CAP) associated with the use of anticholinergic medications in elderly adults.

DESIGN: Nested case-control study.

SETTING: A regional Medicare Advantage healthcare plan (2009-2010).

PARTICIPANTS: Participants were Medicare Advantage Plan enrollees aged 65 and older with at least one inpatient and one outpatient claim with no history of CAP between January 1 and June 30, 2009. Cases were identified as enrollees with an incident diagnosis of CAP, between July 1, 2009, and December 31, 2010 (n = 291). Four age- and sex-matched controls (n = 1,164) were identified per case using incidence density sampling.

MEASUREMENTS: Anticholinergic prescription 30 days preceding the event date was the primary exposure. Anticholinergic exposure was defined based on the Anticholinergic Drug Scale (ADS). A conditional logistic regression model stratified on matched case-control sets was used, with exposure to a Level 1, 2, or 3 anticholinergic on the ADS as the main independent variable; CAP as the main outcome variable; and risk factors for CAP as additional explanatory variables.

RESULTS: After controlling for risk factors, overall use of anticholinergic medications was significantly associated with risk of pneumonia (odds ratio (OR) = 1.65, 95% confidence interval (CI) = 1.20-2.28). The risk of pneumonia remained significant across the different exposure periods, although use of higher-level (ADS Level 2 or 3) anticholinergics was not associated with pneumonia risk (OR = 1.16, 95% CI = 0.70-1.96).

CONCLUSION: Overall use of anticholinergic medications, but not higher-level drugs, was associated with greater risk of CAP compared to no use after controlling for other factors. More research is needed to better understand the role of potent anticholinergic medications on pneumonia risk in elderly adults.