Safety of Anticholinergic Medications in the Elderly
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Objectives: The study objectives were (1) to examine the risk of community-acquired pneumonia in the elderly using anticholinergic medications; (2) to examine the risk of falls/fractures associated with anticholinergic use in the elderly; and (3) to examine the risk of all-cause hospitalization in the above population. Methods: A nested case control design was conducted using regional Medicare data to achieve the study objectives. The base cohort within which the case-control study was nested consisted of persons 65 years of age or older, with at least one inpatient and one outpatient claim anytime during January 1, 2009-June 30, 2009 in which no incidence of study outcome (pneumonia for 1st objective, falls/fractures for 2nd objective and hospitalization for 3rd objective) had occurred. Cases of the primary outcome consisted of those individuals who had a claim for pneumonia (1st objective), falls/fractures (2nd objective) and hospitalization (3rd objective), at least 6 months after entry into the base cohort. For each case, four age and sex-matched controls were identified from the base cohort using incidence density sampling, with a potential for replacement. The primary exposure was defined as a prescription of any anticholinergic medication 30 days before the event date. Anticholinergic exposure was defined based on the pre-validated Anticholinergic Drug Scale (ADS). Conditional logistic regression analyses, stratified on matched case-control sets, was used to model the outcomes, with exposure to anticholinergic Levels 1, 2 or 3 as the main independent variable, and potential confounding factors as additional explanatory variables. Results: Analysis of Medicare data revealed that, there were 291 cases of pneumonia (and 1164 age and sex-matched controls) for the first objective, 449 cases of falls/fractures (and 1796 controls) for the second objective and 295 cases of hospitalization (and 1180 controls) for third objective. After controlling for potential covariates, the results of conditional logistic regression revealed that, use of anticholinergic medications was associated with a marginally higher risk of pneumonia (OR 1.40; 95% CI, 1.03-1.90) compared to non-use. For the second objective, use of anticholinergic medications was not associated with a statistically significant higher risk of falls/fractures (OR 1.03; 95% CI, 0.82-1.31) compared to non- use. The risk of hospitalization was also similar for anticholinergic users (OR 0.85; 95% CI, 0.62-1.17) compared to non-users. No difference in risk was observed across levels of anticholinergic potency for each aim. Conclusion: The current nested case-control study in a cohort of regional Medicare advantage plan beneficiaries found that, use of anticholinergic medications was associated with a marginally higher risk of pneumonia compared to non-use, after controlling for other potential risk factors. However, there was no difference in risk of falls/fractures and all-cause hospitalization with use of anticholinergic agents compared to non-use. Future studies are required to confirm the study findings.