Background: Overactive bladder is a condition that can negatively impact the quality of life in older adults. Treatment with antimuscarinics can mitigate the symptoms of overactive bladder. Older antimuscarinics, such as oral oxybutynin, are thought to be associated with cognitive impairment, while newer antimuscarinics do not appear to be associated with this risk. However, available studies have limitations which suggest that further research is needed.

Objectives: 1) To explore biases, such as confounding by indication and attrition bias, with initiating and discontinuing antimuscarinics in regard to cognitive impairment and 2) to assess the association between older versus newer antimuscarinics and cognitive impairment.

Methods: Using the Medicare Chronic Disease Warehouse 5% random sample from 2007 to 2012, biases will be assessed using a cohort study design of antimuscarinic new-users, and the association with older versus newer antimuscarinics and cognitive impairment will be assessed using Cox proportional hazards models following inverse probability of treatment weighting.

Results: Confounding by indication appears to be (minimally) present in patients who were initiated on newer versus older antimuscarinics with cognitive impairment (RR 1.05, 95% CI 1.03-1.06). Patients who were initiated on older antimuscarinics were more likely to discontinue therapy compared to patients who were initiated on newer antimuscarinics (HR 1.18, 95% CI 1.15-1.21); moreover, patients who were coded for cognitive impairment were more likely to discontinue therapy compared to patients who were not coded for cognitive impairment (HR 1.24, 95% CI 1.13-1.35), suggesting the potential for attrition bias. There were no differences in the development of cognitive impairment in patients who were initiated on older versus newer antimuscarinics after incorporating inverse probability of treatment weighting; however, there was a potential signal that suggested a difference in patients who were initiated on older versus newer antimuscarinics when assessing the outcome of memory loss (HR 2.08, 95% CI 1.02-4.24).

Implications for Public Health: These findings suggest the need for continued research on antimuscarinics and cognitive impairment using larger populations and more refined definitions of cognitive impairment. These results can be used to help inform physician prescribing habits, guidelines, and policies that impact older adults.