Relationship between metabolic syndrome and overactive bladder: insights from the NHANES and Mendelian randomization study

Clinical observations suggest a correlation between metabolic syndrome (Mets) and overactive bladder (OAB). However, the absence of evidence for a direct causal relationship between them limits the development of effective treatment strategies. This study aimed to explore the association between Mets and OAB in the U.S. population and elucidate their causal relationships. A cross-sectional study was conducted using data from the 2005–2018 National Health and Nutrition Examination Survey (NHANES). OAB symptoms were assessed using the OAB symptom score (OABSS), and Mets was diagnosed based on the NCEP-ATP III criteria. Multivariate logistic regression was used to evaluate the relationship between Mets and OAB. Subgroup analyses and interaction tests were performed to assess the consistency of this association. Mendelian randomization (MR) analysis was conducted to investigate the causal effects of Mets components or risk factors on OAB symptoms, including bladder calcification /contracture/ overactivity (BCCO) and urinary frequency/incontinence (UFI). The cross-sectional study involved 7,596 participants. After adjusting for covariates, individuals with Mets had a significantly higher risk of OAB (OR: 2.27, 95% CI: 1.89–2.72, p = 0.035). Gender subgroup analysis revealed that females had 51% higher odds of developing OAB compared to the reference group (OR: 1.51, 95% CI: 1.13–2.02, p = 0.008), while this association was not observed in males (OR: 0.95, 95% CI: 0.63–1.43, p > 0.05). MR analysis found no significant causal relationship between Mets and OAB symptoms; however, certain Mets components or risk factors, including BMI, waist circumference (WC), fasting blood glucose (FBG), and hypertension, were associated with an increased risk of OAB. The sensitivity analysis excluded the influence of potential heterogeneity and horizontal pleiotropy. This study highlighted a positive association between Mets and OAB in the U.S. population, with significant gender differences. Furthermore, it provided evidence suggesting a potential causal role of Mets components in the development of OAB and highlighted the importance of therapeutic strategies targeting Mets for managing OAB symptoms.