Different associations of height-adjusted and BMI-adjusted muscle mass indices with physical function and locomotive health in community-dwelling older adults.
BACKGROUND We compared the associations of height-adjusted appendicular skeletal muscle mass and body mass index-adjusted appendicular skeletal muscle mass with muscle strength, physical performance, and locomotive function-related outcomes in community-dwelling older adults. METHODS This cross-sectional study included 193 adults aged 65-89 years. Participants were classified into four groups according to low appendicular skeletal muscle mass adjusted for height squared and/or body mass index based on the Asian Working Group for Sarcopenia 2025 criteria. Associations between muscle mass indices and physical performance measures, including grip strength, knee extension strength, gait speed, and two-step test performance, were examined using age- and sex-adjusted linear regression analyses. As EuroQol 5 Dimensions and 25-item Geriatric Locomotive Function Scale scores showed ceiling effects, these outcomes were dichotomized and analyzed using logistic regression. RESULTS Low muscle mass was identified in 45 participants using height-adjusted appendicular skeletal muscle mass and in 34 using body mass index-adjusted appendicular skeletal muscle mass, with only nine participants meeting both criteria. Participants with low height-adjusted appendicular skeletal muscle mass alone showed lower body mass index and body fat percentage despite preserved physical performance. Conversely, those with low body mass index-adjusted appendicular skeletal muscle mass alone showed higher adiposity and worse physical performance. In adjusted analyses, body mass index-adjusted appendicular skeletal muscle mass was more strongly associated with grip strength, knee extension strength, and two-step test performance, whereas height-adjusted appendicular skeletal muscle mass showed stronger associations with worse EuroQol 5 Dimensions and locomotive dysfunction assessed via the 25-item Geriatric Locomotive Function Scale. CONCLUSIONS Height-adjusted and body mass index-adjusted appendicular skeletal muscle mass showed different associations with physical performance and locomotive outcomes in older adults. Body mass index-adjusted muscle mass was more closely associated with performance-based physical function, whereas height-adjusted muscle mass was more strongly associated with self-reported health status and locomotive dysfunction.