Cognitive deficits are one of the core features of older-age bipolar disorder (OABD). Psychotropic medications may influence cognition, especially in older populations, where anticholinergic effects are relevant. This cross-sectional study aimed to investigate the potential impact of anticholinergic load on cognitive performance in individuals with OABD.

One hundred and twenty-one euthymic or partially remitted OABD patients were included. Cognitive performance was assessed using a neuropsychological battery and summarized into attention, processing speed, working memory, visual and verbal memory, and executive functions. Anticholinergic load was assessed using the CRIDECO Anticholinergic Load Scale (CALS), and pharmacological burden was quantified using the defined daily dose (DDD). Associations were examined using hierarchical multivariable linear regression models, considering also relevant clinical covariates.

The interaction between CALS and DDD was associated with lower visual and verbal memory scores (p = 0.04). Age was inversely associated with cognitive performance across all domains (all p < 0.01). A higher number of manic episodes was associated with poorer attention, visual and verbal memory, and processing speed (all p < 0.01). Lifetime psychotic symptoms were associated with worse working memory (p = 0.02), and higher diazepam-equivalent doses were associated with worse visual and verbal memory performance (p = 0.02).

Although anticholinergic medications may contribute to cognitive burden, their impact appears dose-related and limited compared with the broader influence of illness-related factors. In OABD patients, prioritizing the management of illness-related characteristics alongside careful pharmacological management may therefore be crucial for preserving cognitive functioning.