The Role of Body Mass Index and Insulin-Treated Diabetes on the Education-Mediated Risk of Developing Stress Urinary Incontinence: A Mediation Mendelian Randomization Study

Background: This study aimed to investigate the causal relationship between educational attainment and stress urinary incontinence (SUI) using Mendelian randomization (MR) analysis, as well as to explore the potential mediating roles of body mass index (BMI), chronic obstructive pulmonary disease (COPD), and insulin-treated diabetes. Methods: Genome-wide association studies (GWAS) data for educational attainment levels were obtained from the Social Science Genetic Association Consortium (SSGAC); SUI data were sourced from the Integrative Epidemiology Unit Open GWAS Project (IEU OpenGWAS project); and data for BMI, COPD and insulin-treated diabetes were obtained from the FinnGen database. The inverse variance weighted (IVW) method was used as the primary analytical approach to investigate causal relationships. Sensitivity analyses, including heterogeneity tests, pleiotropy tests, funnel plot, and leave-one-out sensitivity analysis, were conducted to assess the robustness of the results. Results: A causal relationship was observed between higher educational attainment and a reduced risk of SUI (odds ratio OR = 0.995, 95% CI: 0.993–0.996, p = 1.851 × 10-10). Besides, higher educational attainment was associated with lower BMI (OR = 0.817, 95% CI: 0.792–0.843, p = 4.825 × 10-37) and diabetes (OR = 0.661, 95% CI: 0.615–0.709, p = 2.266 × 10-30). Genetically predicted higher BMI (OR = 1.002, 95% CI: 1.000–1.003, p = 0.048) and insulin-treated diabetes (OR = 1.001, 95% CI: 1.000–1.002, p = 0.012) were associated with an increased risk of SUI. Sensitivity analyses confirmed the robustness of the findings. Mediation analyses showed that BMI (8.08%, p = 0.048) and insulin-treated diabetes (7.47%, p = 0.004) partially mediated the protective effect of higher educational attainment on SUI risk. Conclusions: Improving educational attainment levels may reduce the risk of SUI. Furthermore, BMI and insulin-treated diabetes partially mediate the protective effect of higher educational attainment on SUI risk.