Association of Vitamin D Levels and Mortality in Overactive Bladder: Nonlinear Dose-Response and Threshold Effect

The relationship between 25-hydroxyvitamin D [25(OH)D] and overall and cause-specific mortality among patients with overactive bladder (OAB) remains unclear. This study aimed to clarify whether serum 25(OH)D levels were associated with all-cause and cardiovascular disease (CVD) mortality in patients with OAB. We analyzed data from patients with OAB enrolled in the 2005-2018 National Health and Nutrition Examination Survey (NHANES). We used the Cox proportional hazards regression model to explore the associations between 25(OH)D levels and overall and CVD mortality in patients with OAB. We visualized this relationship using restricted cubic splines (RCS) and further determined the threshold using piecewise functions. Of the 4681 eligible participants, 745 overall and 219 CVD deaths occurred. Multivariate Cox regression adjustment revealed an L-shaped relationship between serum 25(OH)D concentration and overall mortality and a U-shaped relationship with CVD mortality. The breakpoint for all-cause mortality was 66.82 nmol/L, and that for CVD mortality was 119.06 nmol/L. Relative to the lower group, the all-cause mortality risk in the higher concentration group (≥ 66.82 nmol/L) decreased by 27% (HR = 0.73, 95% CI: 0.62-0.85) in patients with OAB. Among patients with OAB, serum 25(OH)D shows an inverse, non-linear association with overall and CVD mortality, for which the thresholds for overall and CVD mortality are 66.82 and 119.06 nmol/L, respectively. Our study provides reference values for the health management of patients with OAB, but further confirmation is still required through randomized controlled trials.