Association between truncal muscle mass index measured by bioelectrical impedance analysis and overactive bladder symptoms in men: A retrospective cross-sectional analysis.

Purpose: This study aimed to investigate the relationship between truncal muscle mass, particularly the skeletal truncal muscle mass index (sTMI), and overactive bladder (OAB) symptoms in adult men, using bioelectrical impedance analysis (BIA).

Materials and methods: We retrospectively analyzed health screening data from 5,475 men aged ≥40 years collected between 2014 and 2022. OAB was defined as an OAB Symptom Score (OABSS) ≥3 and urgency score ≥2, with moderate-to-severe OAB defined as OABSS ≥6 and urgency score ≥2. Body composition metrics, including fat-free mass (FFM), total muscle mass (TMM), and truncal muscle mass (whole and skeletal), were measured via BIA. The sTMI was calculated by dividing skeletal truncal muscle mass by body mass index (BMI). Logistic regression and receiver operating characteristic (ROC) analyses were conducted to assess predictors of OAB.

Results: The overall OAB prevalence was 10.6%. In univariate analysis, FFM (odds ratio [OR] 0.983, p=0.013), TMM (OR 0.982, p=0.010), and sTMI (OR 0.447, p=0.025) were inversely associated with OAB symptoms. However, in multivariate analysis, only sTMI remained a significant independent predictor of moderate-to-severe OAB (OR 0.486, p=0.036). ROC analysis showed that sTMI had better predictive performance for severe OAB (area under the curve [AUC] 0.721) compared to age (AUC 0.706).

Conclusions: sTMI, a BIA-based index reflecting truncal skeletal muscle normalized to BMI, is an independent predictor of moderate-to-severe OAB in men. This suggests a potential role of muscle composition in OAB pathophysiology and risk stratification.