Nonlinear associations between obesity indices and fall risk in middle-aged and older Chinese adults: a cross-sectional analysis based on CHARLS

BackgroundFalls are a leading cause of disability and mortality among older adults in China. The mechanisms linking various obesity indices--such as BMI, Waist-to-Height Ratio (WHtR), Body Roundness Index (BRI), and Body Fat Percentage (BFP) -- to fall risk remain unclear. Given the limitations of BMI, it is important to investigate the influence of body composition and central obesity indicators on fall risk. MethodsThis cross-sectional study used data from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2016; n = 27,303). Logistic regression, restricted cubic spline (RCS) modeling, and piecewise regression were applied to explore the nonlinear associations between obesity indices and falls. Covariates including demographic and health-related factors were adjusted for in multivariate models. ResultsWHtR, BRI, and BFP were nonlinearly associated with fall risk, while BMI showed no significant relationship. Inflection points were observed at 0.504 for WHtR, 3.06 for BRI, and 28.6% for BFP. Below these thresholds, increases in WHtR and BFP were associated with reduced fall risk; above the thresholds, fall risk increased significantly. Subgroup analyses indicated stronger associations among women, rural residents, and individuals with arthritis. ConclusionOur findings identify WHtR, BRI, and BFP as more sensitive predictors of fall risk than BMI. Thresholds of BRI [≥] 3.0 and BFP [≥] 28% may serve as clinical screening markers for fall prevention, supporting a shift from BMI-centric to integrated body composition-function assessments.