Urinary heavy metal burden and overactive bladder risk: a cross-sectional study based on NHANES 2005-2018

Objective: We aimed to explore the relationship between urinary heavy metals and overactive bladder (OAB) among U.S. adults. Method: Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 2005-2018. Concentrations of heavy metals in urine were determined by laboratory tests and corrected for urinary creatinine using natural logarithm (ln) transformation. OAB was assessed using questionnaires. The association between each urinary heavy metal and OAB was first explored using multivariate logistic regression, followed by nonlinear correlation analyses and smoothed curve fitting, with stratified analyses and interaction tests for age and sex. In addition, weighted quantile sum (WQS) regression and quantile-based g-computation (qgcomp) analyses were implemented to explore the relationship between mixed heavy metal and OAB. Results: A total of 9086 participants were included in the final study. Multifactorial logistic regression analysis showed that cobalt (Co), lead (Pb), cadmium (Cd), and uranium (Ur) were positively associated with the risk of developing OAB, whereas barium (Ba) and thallium (Tl) were negatively associated with OAB. Nonlinear correlation analysis showed that the associations between the concentrations of Ba and Tl and OAB risk were nonlinear, and Pb, antimony (Sb), tungsten (Tu), Ur, and Cd showed significant positive correlations with OAB. WQS regression showed that OAB risk increased with increasing quartiles of the WQS index (odds ratio (OR) 1.202, 95% confidence interval (CI) 1.064, 1.357), with Cd showing the strongest positive correlation with OAB. When the mixture effect was constrained to be negative, an increase in the WQS index quartile corresponded to a 14.3% reduction in OAB risk (OR 0.857, 95% CI 0.778, 0.943), with Ba standing out as the most dominant. The results of qgcomp analysis showed that Cd had the largest positive weight of 0.5098, and Ba had the largest negative weight of 0.5976. Conclusion: Urinary heavy metals are significantly associated with OAB risk among U.S. adults. The metal contributing most to the positive correlation with OAB risk is Cd, while the metal contributing most to the negative correlation with OAB risk is Ba.