U-Shaped Association between the Monocyte-to-Albumin Ratio and Overactive Bladder

Introduction: This study was designed to examine the relationship between the monocyte-to-albumin ratio (MAR) and overactive bladder (OAB) prevalence. Methods: This investigation utilized data from the National Health and Nutrition Examination Survey (NHANES), comprising 34,772 participants aged 20 years or older. We employed multivariate logistic regression, smooth curve fitting, subgroup, and sensitivity analyses to examine the relationships between MAR and OAB. Results: A positive relationship was observed between ln(MAR) and OAB (overall OR: 1.20; 95% CI: 1.11–1.30). However, a significant U-shaped association was identified through the smooth curve fitting analysis (p for likelihood ratio test <0.001; inflection point at ln(MAR) = −2.64). A threshold effect analysis confirmed this pattern: ln(MAR) was negatively associated with OAB below this threshold (OR: 0.54; 95% CI: 0.34–0.87) but positively associated above it (OR: 1.27; 95% CI: 1.16–1.39). The area under curve (AUC) of ln(MAR) was higher than those for NAR, SIRI, MLR, NMLR, NLR, and SII. Compared to various traditional inflammatory markers (such as NLR, MLR, SII, SIRI, etc.), ln(MAR) demonstrated superior discriminative ability for OAB prevalence (AUC = 0.555). Assessment across subgroups showed that the connection between ln(MAR) and OAB was particularly significant in older adults (≥60 years) and individuals with a poverty-income ratio of <1.3. Conclusions: Our analysis identified a U-shaped relationship between the MAR and OAB, and the MAR may serve as biomarkers for assessing OAB prevalence.