Association of Handgrip Strength With Urinary Incontinence in Postmenopausal Korean Women: A Machine Learning Study.

Introduction and hypothesis: Urinary incontinence (UI) is a common condition in older women and is associated with frailty and functional decline. Handgrip strength is a simple, noninvasive marker of muscle function that may help identify women at risk for UI. This study aimed to examine the association between handgrip strength and UI in postmenopausal Korean women and evaluate its predictive utility using machine learning models.

Methods: We analyzed data from 4213 postmenopausal women aged ≥45 years who participated in the Korean Longitudinal Study of Aging (2006 -2022). UI was defined as reporting urine leakage on ≥5 days during the past month. Handgrip strength was measured using a standardized digital dynamometer protocol. Five machine learning models-logistic regression, random forest (RF), support vector machine, extreme gradient boosting (XGB), and deep neural network-were used to predict UI. Model performance was evaluated using fivefold cross-validation. Logistic regression and generalized additive models were used to validate findings.

Results: Among postmenopausal women, the prevalence of UI was 26.0%. Compared to the continent group, individuals with UI were older (73.5 ± 6.7 vs. 68.3 ± 6.1 years, p < 0.001), exhibited lower handgrip strength (20.4 ± 4.8 vs. 22.5 ± 4.9 kg, p < 0.001), and had a higher burden of comorbidities and functional impairments. In multivariable logistic regression models adjusting for age, BMI, and other demographic, clinical, lifestyle, and frailty-related symptom variables, lower handgrip strength remained independently associated with UI (adjusted OR 0.971, 95% CI 0.951-0.992 per 1 kg decrease). RF and XGB models demonstrated robust predictive performance, with AUCs of 0.887 and 0.860, respectively. A handgrip strength threshold of 15.75 kg was identified as a clinically relevant cutoff below which UI risk increased.

Conclusion: Handgrip strength is independently associated with UI in postmenopausal women. As a practical and noninvasive measure, it may be useful in identifying individuals at increased risk of incontinence and guiding early interventions.