Current evidence suggests that overweight and obesity are important risk factors for urinary incontinence in women. However, little is known about the relationships between body mass index (BMI), physical activity and urinary incontinence in women in their 20s.
The aims were to: 1) compare prevalence rates of urinary incontinence and high BMI in two cohorts of young women; 2) explore associations between changes in BMI and urinary incontinence using analysis of combined data from the two cohorts; and 3) explore the associations between physical activity and urinary incontinence, with adjustment for BMI.
and Methods: Data were from two cohorts of young women in the Australian Longitudinal Study of Women’s Health (n=16,065), born 17 years apart: 1973-78 (Cohort 1) and 1989-95 (Cohort 2). The women in both cohorts completed surveys at age 18-23 years (T1), with follow up four years later (age 22-27, T2). Self-reported urinary incontinence and BMI were assessed in both surveys. As PA was measured using different questions in Cohort 1 at T1, self-reported physical activity data were from T2 only. Nine BMI transition categories (based on BMI status at baseline and follow up) and four physical activity categories, were created to assess multivariate-adjusted prevalence ratios for urinary incontinence at T2, using Poisson regression.
Rates of obesity increased in both cohorts over four years, from 6.6%% (95% CI 6.1-7.2) to 10.4% (95% CI 9.7-11.0) in Cohort 1 and from from 11.7% (95% CI 11.0-12.4) to 19.6% (95% CI 18.7-20.5) in Cohort 2. Compared with women who maintained normal BMI at T1 and T2, the prevalence ratio (PR) for UI among those with BMI>30 at age 22-27 was higher, regardless of BMI category at age 18-23: [prevalence ratio (PR) for normal BMI at T1, 1.39, 95%CI 1.1-1.76; PR for overweight at T1, 1.44, 95%CI 1.27-1.63; PR for obese at T1, 1.51, 95%CI 1.36-1.67]. In Cohort 1, there was no relationship between physical activity and UI. However, in Cohort 2 there was an inverse dose response relationship between physical activity and UI.
The strong association between obesity and urinary incontinence in young women is a public health concern, given that obesity rates are likely to increase further with age and parity. The potential mitigating effects of physical activity on the obesity-incontinence relationship merit further investigation.

Copyright © 2021. Published by Elsevier Inc.