Association between systemic immune-inflammation index and urinary incontinence: Evidence from the National Health and Nutrition Examination Survey

Objective This study examined the association between the systemic immune-inflammation index and urinary incontinence subtypes using data from National Health and Nutrition Examination Survey 2007–2016. Methods This cross-sectional study included 21,569 adults. Systemic immune-inflammation index was calculated and log-transformed. Survey-weighted logistic regression analyses, smoothed curve fitting, exploratory threshold analyses, and subgroup analyses stratified by demographic and clinical characteristics were conducted to evaluate its associations with stress urinary incontinence, urgency urinary incontinence, and mixed urinary incontinence. Results Higher log 10 systemic immune-inflammation index levels were significantly associated with an increased prevalence of stress urinary incontinence. Associations with urgency urinary incontinence and mixed urinary incontinence were weaker, and quartile trends were not statistically significant. Smoothed curve fitting demonstrated monotonic increases for stress urinary incontinence and mixed urinary incontinence, whereas a nonlinear pattern was observed for urgency urinary incontinence, suggesting a potential threshold at a log 10 systemic immune-inflammation index of approximately 2.5. Conclusion Elevated systemic immune-inflammation index levels were significantly associated with stress urinary incontinence, whereas associations with urgency urinary incontinence and mixed urinary incontinence were weaker and exhibited nonlinear patterns. Longitudinal studies are required to clarify the temporal relationships underlying these associations.