To explore the relationship between  frailty and overactive bladder (OAB) by using a large-scale population in the United States and GWAS data.

Data from 8,177 participants in the 2005–2018 NHANES cycles were analyzed. Frailty was assessed using a 49-item frailty index and categorized into four groups. OAB was defined using OABSS ≥3 based on urinary symptoms. Weighted multivariate logistic regression was performed to explore the association between frailty and OAB. LD score regression (LDSC) and High Definition Likelihood (HDL) analyses were conducted using publicly available genome-wide association studies (GWAS) summary data to evaluate genetic correlation and potential causality. All statistics were performed in R software with P < 0.05 considered significant.

Among 8,177 NHANES participants, OAB and non-OAB groups differed significantly in multiple characteristics except smoking. Multivariate logistic regression showed a graded positive association between frailty and OAB (Frail: OR = 4.79, 95% CI: 3.60-6.36, P < 0.001; Most Frail: OR = 9.10, 95% CI: 6.37-13.00, P < 0.001). Restricted cubic spline analysis confirmed a threshold‑dependent dose‑response relationship. Genetic correlation analysis indicated a genetic association between frailty and OAB (LDSC: P = 0.019; HDL: P = 2.378e-35).

After adjusting for confounders, frailty severity was independently and dose‑dependently associated with higher odds of OAB, suggesting frailty may be a clinically meaningful risk factor for OAB. The significant genetic correlations observed in both LDSC and HDL analyses imply that the phenotypic association is not merely coincidental but may share common genetic underpinnings, supporting potential shared biological pathways between frailty and overactive bladder.

This study provides consistent epidemiological and genetic evidence supporting a close relationship between frailty and OAB. Increasing frailty severity is independently associated with a significantly elevated OAB risk in a dose‑dependent manner. Moreover, significant genetic correlations identified by LDSC and HDL suggest shared genetic architecture between the two conditions. These findings underscore the clinical importance of frailty screening in individuals at risk for OAB and support further investigation into common biological pathways.