BMI-adjusted handgrip strength as a functional index to assess fall risk among older adults

This study was devised to explore how body mass index-adjusted handgrip strength (HGS/BMI) is related to subsequent fall risk among older Chinese adults, while also examining whether HGS/BMI demonstrates more consistent associations and more stable sex-specific associations than absolute HGS. A prospective cohort study. Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS). Muscle strength at baseline (2011) was evaluated based on absolute HGS (kg) and HGS normalized to body mass index (BMI, kg/m 2 ) as the HGS/BMI ratio. Self-reported falls during follow-up served as the primary outcome. Baseline demographic variables and physician-confirmed chronic diseases were included as covariates. A total of 4,978 participants were analyzed, including 2,510 men and 2,468 women. During follow-up, self-reported falls during follow-up occurred in 14.80% of men and 22.37% of women. In multivariable logistic regression analyses treating muscle strength indices as continuous variables, each 1-unit increase in HGS was associated with a 2.3% reduction in fall risk among men (OR = 0.977, 95% CI: 0.963–0.992, P = 0.003), whereas no statistically significant association was observed in women (OR =0.991, 95% CI: 0.975–1.008, P = 0.297). In contrast, higher continuous HGS/BMI values were significantly associated with lower fall risk in both men (OR = 0.698, 95% CI: 0.513–0.951, P = 0.023) and women (OR = 0.700, 95% CI: 0.504–0.973, P = 0.034). When analyzed categorically, men in the low HGS group exhibited a significantly elevated fall risk (OR = 1.788, 95% CI: 1.354–2.360, P < 0.001), whereas this association faded toward non-significance in women (OR = 1.246, 95% CI: 0.966–1.608, P = 0.091). Crucially, when evaluated using quartile-based stratified categories, the low HGS/BMI group remained independently and significantly associated with an increased risk of self-reported falls during follow-up in both men (OR = 1.391, 95% CI: 1.015–1.905, P = 0.040) and women (OR = 1.331, 95% CI: 1.006–1.762, P = 0.045) compared to their respective high HGS/BMI counterparts. Compared with absolute HGS, HGS/BMI demonstrated more robust and consistent longitudinal associations with fall risk across both continuous and categorical models, successfully accounting for body size in muscle function assessment. Notably, absolute strength metrics completely lost statistical significance in predicting fall risk among women when evaluated both continuously and categorically, whereas HGS/BMI consistently retained significant predictive value in all models. These findings indicate that BMI-adjusted muscle strength indicators offer superior clinical utility, serving as a rational conceptual extension of the evolving AWGS 2025 framework from muscle mass to muscle function, and facilitating the early screening of high-risk individuals whose vulnerability may be masked or underestimated by absolute strength measurements alone.