BACKGROUND: Few studies have examined the relationships between body mass index (BMI), physical activity (PA), and urinary incontinence (UI) in young women. Most research on modifiable risk factors for UI has focused on mid-aged and older women.
METHODS: Participants were from two cohorts of young women in the Australian Longitudinal Study of Women’s Health (ALSWH; n=16,065), born 17 years apart: 1973-1978 (cohort 1) and 1989-1995 (cohort 2). Data were from surveys completed at age 18-23 years (T1), and age 22-27 years (T2). Participants reported UI, height and weight at T1 and T2, and PA levels at T2 only. BMI transition categories (based on BMI at T1 and T2) and physical activity categories (nil, low, moderate, high) were created, and included in Poisson regression analysis to calculate multivariate-adjusted prevalence ratios (PR) for UI at T2.
RESULTS: Prevalence rates of obesity and UI were much higher in cohort 2 than cohort 1. The prevalence of obesity at T2 was 10.4% in cohort 1 and 19.6% in cohort 2, and the prevalence of UI was 16.4% and 30.4%, respectively. Obesity at T2 was associated with higher prevalence of UI, regardless of BMI at T1 (BMI <25 at T1, PR 1.39 [95% confidence interval (CI), 1.1-1.76]; overweight at T1, PR 1.44 [95% CI, 1.27-1.63]; and obese at T1, PR 1.51 [95% CI, 1.36-1.67]). There was no relationship between PA and UI in cohort 1. However, in cohort 2 there was an inverse dose-response relationship between PA and UI, after adjusting for BMI.
CONCLUSION: The strong association between obesity and UI in young women is a public health concern, given the much higher prevalence in the current generation of young women. Further research is needed to explore the potential mitigating effects of PA on the obesity-incontinence relationship in this demographic group.