Association between Anticholinergic Medication Use and Risk of Dementia among Patients with Parkinson's Disease

Study Objectives: To evaluate the association between anticholinergic medication use, categorized by anticholinergic cognitive burden (primary objective) and cumulative dose (secondary objective), and the risk of developing dementia among patients with Parkinson's disease. Design: Retrospective cohort study with an active comparator design. Data Source: National Health Insurance Research Database in Taiwan (2001–2011). Patients: A total of 1232 adults with Parkinson's disease who were diagnosed between 2002 and 2004 and taking at least one antiparkinson medication during this period were included. Of these patients, 694 were exposed to anticholinergic medications categorized as mild (reference group), and 538 were exposed to anticholinergic medications categorized as moderate or severe (exposure group). Measurements and Main Results: Exposure to different types of anticholinergic medications was categorized by using the Anticholinergic Cognitive Burden (ACB) scale, and cumulative doses of anticholinergic medications were measured by using the cumulative minimum doses (cMD) method. Associations between anticholinergic medication use and risk of dementia were assessed by multivariable Cox proportional hazards models. The type of anticholinergics used (moderate or severe vs mild ACB) was not significantly associated with an increased risk of developing dementia (hazard ratio [HR] 0.97, 95% confidence interval [CI] 0.72–1.27). After adjusting for confounders, a high cumulative dose of anticholinergic drug (> 1095 cumulative minimum doses [cMDs]) was found to be significantly associated with an increased risk of developing dementia when compared with a low cumulative dose of anticholinergic drug (≤ 90 cMDs) (HR 3.06, 95% CI 1.35–6.97). Conclusion: Among patients with Parkinson's disease in Taiwan, those with a high cumulative dose of anticholinergics had an increased risk of being diagnosed with dementia. Physicians should consider prescribing the lowest therapeutic dose of anticholinergic medication when making treatment decisions for patients with Parkinson's disease.