Background: The differential risk of incident dementia associated with receiving various overactive bladder (OAB) drugs is unknown.

Objective: To estimate the association of antimuscarinic OAB drug (exposure), compared with a β-3 agonist (mirabegron), and incident dementia.

Design, setting, and participants: A population-based nested case-control study was conducted in patients treated with OAB medications in Ontario, Canada. A total of 11 392 patients aged ≥66 yr with a new diagnosis of dementia between 2010 and 2017, and 29 881 age- and sex-matched controls without dementia were included in the study.

Intervention: Receipt of an antimuscarinic OAB drug or receipt of mirabegron, within the previous 6-12 mo.

Outcome measurements and statistical analysis: Cases developed dementia and Alzheimer's disease. Controls were derived from the general population and matched to cases based on important baseline characteristics. Odds ratios (ORs) for incident dementia, adjusted for demographic and health-related characteristics, were determined.

Results and limitations: Patients receiving solifenacin (OR 1.24; 95% confidence interval 1.08-1.43) and darifenacin (OR 1.30; 95% CI 1.08-1.56) in the prior 6 mo had increased odds of incident dementia compared with those receiving mirabegron. In the 6 mo to 1 yr prior to diagnosis, receipt of solifenacin (OR 1.34; 95% CI 1.11-1.60), darifenacin (OR 1.49; 95% CI 1.19-1.86), tolterodine (OR 1.21; 95% CI 1.02-1.45), and fesoterodine (OR 1.39; 95% CI 1.14-1.71) was associated with increased odds of incident dementia compared with receipt of mirabegron. No effect was seen with oxybutynin or trospium. Limitations included misclassification of the outcome and residual confounding associated with the use of health administrative databases.

Conclusions: Older adults receiving solifenacin and darifenacin in the 6 mo prior to diagnosis, and those receiving solifenacin, darifenacin, tolterodine, or fesoterodine in the year prior to diagnosis, have increased odds of incident dementia, compared with those receiving mirabegron. Oxybutynin and trospium were not associated with dementia, likely due to a protopathic bias. Careful drug selection is warranted when treating patients with OAB.

Patient summary: In a large Canadian cohort of patients who developed dementia after starting an overactive bladder (OAB) medication, those taking some anticholinergic medications for OAB have an increased risk of dementia compared with those taking mirabegron.