Supplementary Material for: The interaction effect of obesity with sleep duration on urinary incontinence in adult females: a cross-sectional study of the NHANES database

Introduction: This study aims to explore the interaction between obesity and sleep duration on UI in adult women.
Methods: Data of adult females were extracted from the National Health and Nutrition Examination Surveys (NHANES) database in 2005-2018 in this cross-sectional study. Weighted univariate and multivariate logistic regression analyses were utilized to screen covariates and investigate the associations of obesity and sleep duration with 3 types of UI, including stress urinary incontinence (SUI), urgency urinary incontinence (UUI), and mixed urinary incontinence (MUI). In addition, the interaction effect between obesity and sleep duration on UI was assessed. The evaluation indexes were odd ratios (ORs) and 95% confidence intervals (CIs), relative excess risk due to interaction (RERI), attributable proportion of interaction (AP) and synergy index (S).
Results: Among 13,692 eligible women, 6,063 had SUI, 4,370 had UUI, and 2,621 had MUI. After adjusting for the covariates, women with obesity had higher odds of SUI (OR=1.78, 95%CI: 1.59-2.00), UUI (OR=1.84, 95%CI: 1.63-2.06), and MUI (OR=1.67, 95%CI: 1.48-1.88), compared with those who without obesity. Similarly, comparing to adequate sleep, sleep deprivation and hypersomnia were both significantly linked to higher odds of all types of UI (all P<0.05). The restricted cubic spline (RCS) curves showed there is a U-shaped association of sleep duration with UUI and MUI respectively (all non-line P<0.05). In addition, there was a potential synergistic effect between obesity and hypersomnia on UUI (RERI=0.576, AP=0.243, S=1.729), and that on MUI (RERI=0.821, AP=0.339, and S=2.373).
Conclusions: Obesity and hypersomnia had a potential synergistic effect on UI, especially UUI and MUI. Adult women should adopt measures to keep BMI within normal range, and timely intervene hypersomnia to reduce the possible risk of UI.