Systemic Immune‐Inflammation Index and Neutrophil‐To‐Lymphocyte Ratio: U‐Shaped Association With Overactive Bladder

Objectives This study aims to examine the association of systemic immune‐inflammation index (SII) and neutrophil‐to‐lymphocyte ratio (NLR) with the prevalence of overactive bladder (OAB). Methods This cross‐sectional study analyzed data from 22,343 participants (≥ 20 years) in the National Health and Nutrition Examination Survey (2005–2018). We applied weighted multivariate logistic regression, restricted cubic spline (RCS) regression, subgroup, and sensitivity analyses to assess the associations between SII, NLR, and OAB. Results RCS analysis revealed U‐shaped relationships with inflection points at 6.13 for ln(SII) and 0.65 for ln(NLR). In the fully adjusted model, ln(SII) ≤ 6.13 showed a negative correlation with OAB (OR = 0.83; 95% CI: 0.70–0.99), while ln(SII) > 6.13 was positively correlated (OR = 1.32; 95% CI: 1.10–1.58). Similarly, ln(NLR) > 0.65 correlated positively with OAB (OR = 1.40; 95% CI: 1.16–1.71). Subgroup analyses revealed significant differences in alcohol use subgroups for ln(SII) ≤ 6.13 and ln(NLR) ≤ 0.65 ( P for interaction < 0.05). Conclusions SII and NLR may serve as biomarkers for assessing OAB risk.