Association between body roundness index and urinary incontinence in American adults: A cross-sectional study of NHANES 2001 to 2018

This study aims to investigate the association between Body Roundness Index (BRI) and urinary incontinence (UI) subtypes (stress [SUI], urge [UUI], and mixed [MUI]). This cross-sectional study analyzed NHANES 2001 to 2018 data from 28,639 participants aged ≥20 years. Participants were stratified by BRI quartiles. Multivariable logistic regression examined associations between BRI and UI subtypes. Restricted cubic spline analysis explored nonlinear relationships. Threshold effect analysis identified inflection points. In fully adjusted models, each unit increase in BRI increased risk by 12% for SUI (OR = 1.12, 95% CI: 1.10–1.14) and UUI (OR = 1.12, 95% CI: 1.10–1.13), and 13% for MUI (OR = 1.13, 95% CI: 1.11–1.16) (all P <.0001). Compared to the lowest quartile, the highest quartile showed elevated risks: 109% for SUI (OR = 2.09, 95% CI: 1.88–2.32), 81% for UUI (OR = 1.81, 95% CI: 1.64–2.01), and 113% for MUI (OR = 2.13, 95% CI: 1.85–2.47). Threshold analysis revealed inflection points at BRI = 2.72 for UUI and BRI = 7.8 for SUI and MUI. Below the UUI threshold, association was negative (OR = 0.71, 95% CI: 0.55–0.91); above it, positive (OR = 1.13, 95% CI: 1.11–1.15). Poverty-income ratio moderated the BRI-SUI relationship ( P = .0218). BRI demonstrated significant dose-response associations with all UI subtypes in fully adjusted models. Quartile analysis revealed that the highest BRI quartile showed significant associations across subtypes, with MUI displaying the strongest association. Nonlinear threshold analyses identified subtype-specific inflection points, indicating distinct association patterns for different UI subtypes.