Background: Anticholinergic medication use is associated with cognitive decline and incident dementia. Our study, a prospective birth cohort analysis, aimed to determine if repeated exposure to anticholinergic medications was associated with greater decline, and whether decline was reversed with medication reduction.

Methods: From the Medical Research Council (MRC) National Survey of Health and Development, a British birth cohort with all participants born in a single week of March 1946, we quantified anticholinergic exposure between ages 53 and 69 years using the Anticholinergic Cognitive Burden Scale (ACBS). We used multinomial regression to estimate associations with global cognition, quantified by the Addenbrooke's Cognitive Examination, 3^rd Edition (ACE-III). Longitudinal associations between ACBS and cognitive test results (Verbal memory quantified by the Word Learning Test [WLT], and processing speed quantified by the Timed Letter Search Task [TLST]) at three time points (age 53, 60-64 and 69) were assessed using mixed and fixed effects linear regression models. Analyses were adjusted for sex, childhood cognition, education, chronic disease count and severity, and mental health symptoms.

Results: Anticholinergic exposure was associated cross-sectionally with lower ACE-III scores at age 69, with the greatest effects in those with high exposure at ages 60-64 (mean difference - 2.34, 95% confidence interval [CI] - 3.51 to - 1.17). Longitudinally, both mild-moderate and high ACBS scores were linked to lower WLT scores, again with high exposure showing larger effects (mean difference with contemporaneous exposure - 0.90, 95% CI - 1.63 to - 0.17; mean difference with lagged exposure - 1.53, 95% CI - 2.43 to - 0.64). Associations remained in fixed effects models (mean difference with contemporaneous exposure -1.78, 95% CI -2.85 to - 0.71; mean difference with lagged exposure - 2.23, 95% CI - 3.33 to - 1.13). Associations with TLST were noted only in isolated contemporaneous exposure (mean difference - 13.14, 95% CI - 19.04 to - 7.23; p < 0.01).

Conclusions: Anticholinergic exposure throughout mid and later life was associated with lower cognitive function. Reduced processing speed was associated only with contemporaneous anticholinergic medication use, and not historical use. Associations with lower verbal recall were evident with both historical and contemporaneous use of anticholinergic medication, and associations with historical use persisted in individuals even when their anticholinergic medication use decreased over the course of the study.