Cumulative Anticholinergic Burden and Risk of Delirium Among Older Adults with Alzheimer's Disease

Delirium is a transient neuropsychiatric condition that is a severe and prevalent condition affecting 2.6 million older adults each year. Alzheimer's disease (AD) and anticholinergic medication use are risk factors for delirium. This study evaluated the association between cumulative anticholinergic burden (CAB) and risk of delirium among older adults with AD initiating cholinesterase inhibitors (ChEIs). This retrospective cohort study used 2013-2017 Medicare claims data, and included adults 65 years and older with AD who initiated any of the ChEIs (donepezil, rivastigmine, and galantamine) after a 12-month washout period. CAB, as the primary exposure, was measured on the index date and calculated as the monthly total standardized daily dose of anticholinergic medications. A multivariable Cox proportional hazards regression model with inverse probability of treatment weighting (IPTW) generated using generalized boosted models was used to evaluate the risk of delirium associated with the CAB. This study identified 143,320 older adults with AD who initiated ChEIs. Most patients were in the low/no burden (62.73%) group, followed by high burden (21.12%) and moderate burden (16.14%). Overall, delirium diagnosis was observed in 19.11% of the cohort. The Cox regression model with IPTW found that moderate (aHR, 1.56; 95% CI, 1.52-1.61; p < 0.0001) and high CAB (aHR, 1.45; 95% CI, 1.42-1.49; p < 0.0001) were associated with an increased risk of delirium compared to low/no burden. Among older adults with AD initiating ChEIs, moderate and high CAB were associated with an increased risk of delirium compared with low/no CAB. These findings highlight the need to carefully reduce the CAB, especially dose and duration, along with utilizing anticholinergic alternatives in older adults with AD.