Handgrip strength relative to DXA-measured appendicular lean mass and life functioning in older Korean adults: a nationwide cross-sectional study

Background Muscle strength and muscle quantity may become dissociated with aging, but whether strength relative to directly measured appendicular lean mass is associated with life functioning remains uncertain. We examined whether handgrip strength relative to dual-energy X-ray absorptiometry (DXA)-measured appendicular lean mass was associated with life functioning in older adults. Methods This cross-sectional study used nationally representative data from the 2024 Korea National Health and Nutrition Examination Survey. Participants were 1,133 adults aged 65 years or older with valid DXA-derived appendicular lean mass, maximal handgrip strength, and 10-item Life Functioning Scale (LF-10) data. Within each sex, maximal handgrip strength was regressed on appendicular lean mass using survey weights, and the standardized observed-minus-predicted residual represented relative strength. Survey-weighted regression accounted for sampling weights, strata, and clusters. Secondary, supplementary, and exploratory analyses examined EQ-5D-3L ​utility, phase angle, and falls, respectively. Results The fully adjusted analysis included 1,069 participants. Each 1-standard-deviation higher relative strength was associated with a 2.95-point higher LF-10 score (95% confidence interval [CI], 2.08–3.82; P < 0.001). Compared with the lowest quartile, the highest quartile had a 7.80-point higher LF-10 score (95% CI, 5.62–9.98; P < 0.001). Model-adjusted mean LF-10 scores increased from 85.30 (95% CI, 83.21–87.38) in the lowest quartile to 93.09 (95% CI, 91.87–94.32) in the highest. The association was approximately linear (P for nonlinearity = 0.202) and remained similar across sensitivity analyses. Higher relative strength was also associated with higher EQ-5D utility and phase angle, whereas the association with falls was not statistically significant. Conclusions In older Korean adults, handgrip strength relative to DXA-measured appendicular lean mass was associated with better life functioning. This population-referenced measure may help characterize functional heterogeneity not apparent from muscle quantity alone but does not establish a diagnostic or clinically actionable index. Prospective and external validation are needed before clinical application.