Body Mass Index, Weight Gain, and Incident Urinary Incontinence in Middle-Aged Women

OBJECTIVE: To describe the relations between body mass index (BMI; kg/m(2)), weight gain, and incident urinary incontinence in middle-aged women. METHODS: This was a prospective study in the Nurses' Health Study II. Participants reported their weight at age 18 years, and current weight and height in 1989; weight was updated on subsequent biennial questionnaires. From 2001-2003, incident cases with at least monthly incontinence were identified among 30,982 women aged 37 to 54 years who reported no incontinence in 2001. Information on incontinence type was collected from incident cases with at least weekly incontinence. Multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between BMI in 2001, weight change from age 18 years to 2001, and incident incontinence were estimated using multivariable logistic regression models. RESULTS: Increasingly higher BMI was related to increasing odds of developing incontinence (P for trend<.001). Comparing women with BMI greater than or equal to 35 kg/m(2) with lean women (BMI 21-22.9 kg/m(2)), the OR for at least monthly incontinence was 2.11 (95% CI 1.84-2.42). These increases were similar for all incontinence types. The odds of incontinence also increased with increasing adult weight gain (P for trend<.001); compared with women who maintained their weight within 2 kg, the OR for at least weekly incontinence was 1.44 (95% CI 1.05-1.97) among women who gained 5.1 to 10 kg and 4.04 (95% CI 2.93-5.56) among women who had gained more than 30 kg since early adulthood. We found no effect modification by initial weight in analyses of weight gain from age 18 years to 2001. CONCLUSION: Adiposity and weight gain seem to be strong independent risk factors for incontinence development in middle-aged women. LEVEL OF EVIDENCE: II.