Anticholinergic Drug Exposure and the Risk of Dementia: A Nested Case-Control Study

Key PointsQuestionIs the risk of dementia among persons 55 years or older associated with the use of different types of anticholinergic medication? FindingsIn this nested case-control study of 58769 patients with a diagnosis of dementia and 225574 matched controls, there were statistically significant associations of dementia risk with exposure to anticholinergic antidepressants, antiparkinson drugs, antipsychotic drugs, bladder antimuscarinics, and antiepileptic drugs after adjusting for confounding variables. MeaningThe associations observed for specific types of anticholinergic medication suggest that these drugs should be prescribed with caution in middle-aged and older adults. This nested case-control study including 58769 patients diagnosed with dementia and 225574 matched controls 55 years or older evaluates whether, and to what extent, anticholinergic drug exposure was associated with dementia risk. ImportanceAnticholinergic medicines have short-term cognitive adverse effects, but it is uncertain whether long-term use of these drugs is associated with an increased risk of dementia. ObjectiveTo assess associations between anticholinergic drug treatments and risk of dementia in persons 55 years or older. Design, Setting, and ParticipantsThis nested case-control study took place in general practices in England that contributed to the QResearch primary care database. The study evaluated whether exposure to anticholinergic drugs was associated with dementia risk in 58769 patients with a diagnosis of dementia and 225574 controls 55 years or older matched by age, sex, general practice, and calendar time. Information on prescriptions for 56 drugs with strong anticholinergic properties was used to calculate measures of cumulative anticholinergic drug exposure. Data were analyzed from May 2016 to June 2018. ExposuresThe primary exposure was the total standardized daily doses (TSDDs) of anticholinergic drugs prescribed in the 1 to 11 years prior to the date of diagnosis of dementia or equivalent date in matched controls (index date). Main Outcomes and MeasuresOdds ratios (ORs) for dementia associated with cumulative exposure to anticholinergic drugs, adjusted for confounding variables. ResultsOf the entire study population (284343 case patients and matched controls), 179365 (63.1%) were women, and the mean (SD) age of the entire population was 82.2 (6.8) years. The adjusted OR for dementia increased from 1.06 (95% CI, 1.03-1.09) in the lowest overall anticholinergic exposure category (total exposure of 1-90 TSDDs) to 1.49 (95% CI, 1.44-1.54) in the highest category (>1095 TSDDs), compared with no anticholinergic drug prescriptions in the 1 to 11 years before the index date. There were significant increases in dementia risk for the anticholinergic antidepressants (adjusted OR [AOR], 1.29; 95% CI, 1.24-1.34), antiparkinson drugs (AOR, 1.52; 95% CI, 1.16-2.00), antipsychotics (AOR, 1.70; 95% CI, 1.53-1.90), bladder antimuscarinic drugs (AOR, 1.65; 95% CI, 1.56-1.75), and antiepileptic drugs (AOR, 1.39; 95% CI, 1.22-1.57) all for more than 1095 TSDDs. Results were similar when exposures were restricted to exposure windows of 3 to 13 years (AOR, 1.46; 95% CI, 1.41-1.52) and 5 to 20 years (AOR, 1.44; 95% CI, 1.32-1.57) before the index date for more than 1095 TSDDs. Associations were stronger in cases diagnosed before the age of 80 years. The population-attributable fraction associated with total anticholinergic drug exposure during the 1 to 11 years before diagnosis was 10.3%. Conclusions and RelevanceExposure to several types of strong anticholinergic drugs is associated with an increased risk of dementia. These findings highlight the importance of reducing exposure to anticholinergic drugs in middle-aged and older people.