The use of Metformin in overactive bladder - a retrospective nested case-control, population-based analysis.

OBJECTIVE: To determine if metformin use is associated with a lower rate of overactive bladder (OAB) medication use. Metformin facilitates the proliferation and migration of stem cells, which have been shown to improve bladder overactivity in animal models.

METHODS: We conducted a retrospective nested case-control cohort study using population-based health-care administrative databases. Our cohort included patients with diabetes mellitus type 2 (DM2) ≥ 69 years. Cases received a prescription for an OAB medication, matched with up to 4 controls based on age, sex, and DM2 diagnosis date. Exposure was a new prescription for metformin prior to receiving an OAB medication. Adjusted odds ratios (aOR) were estimated using conditional logistic regression. Sensitivity analysis was done to assess the relationship between cumulative days' supply of metformin and use of OAB medications.

RESULTS: Within our cohort of 2,233,084 patients with DM2, there were 16,549 case subjects who received a prescription for an OAB medication, and 64,171 matched controls. We found a positive association between OAB medication use and metformin use (aOR = 1.07, 95% CI = 1.03-1.12). Summed days' supply of metformin was also associated with OAB medication use, except when summed metformin days was >2220.

CONCLUSIONS: Older patients with DM2 exposed to metformin had a slightly higher rate of OAB medication use, until 2220+ days' metformin supply, whereafter no association was found. This suggests no protective role for metformin in the prevention of OAB in this patient population.