Na Young Yeo, Soo-Young Seo, Heeji Choi, Dong-Hyun Kim, Jae Jun Lee, Hye-Jin Kim, Chulho Kim
Fat-free mass index is a practical marker for low muscle mass screening. However, its accuracy varies by sex and metabolic health, requiring sex-and disease-specific calibration to improve malnutrition diagnosis and sarcopenia screening.
BACKGROUND: The Global Leadership Initiative on Malnutrition criteria has recommended using bioelectrical impedance analysis-derived fat-free mass index as a practical screening tool for low muscle mass. In the present study we evaluated the correlation between this index and dual-energy X-ray absorptiometry-derived appendicular skeletal muscle mass index, and developed sex-specific predictive nomograms according to the 2019 Asian Working Group for Sarcopenia criteria.
METHODS: This cross-sectional analysis included 369 community-dwelling adults from the Hallym Aging Study. Body composition was assessed by bioelectrical impedance analysis and dual-energy X-ray absorptiometry. Low appendicular skeletal muscle mass index was defined as <7.0 kg/m2 for men and <5.4 kg/m2 for women. Receiver operating characteristic analysis identified optimal cutoffs. Multivariable logistic regression and sex-specific nomograms were developed, adjusting for age, albumin, creatinine, hypertension, diabetes, and dyslipidemia. Models were internally validated using 1000 bootstrap resamples.
RESULTS: This index moderately correlated with appendicular skeletal muscle mass index (ρ = 0.65 in males, ρ = 0.36 in females; P < 0.001). Optimal cutoffs were 17.7 kg/m2 for males (area under the curve, 0.84) and 16.1 kg/m2 for females (0.73). This index remained independently associated with low appendicular skeletal muscle mass index after multivariable adjustment. Nomograms showed good discrimination (C-statistics = 0.78 in males, 0.73 = in females) and calibration. In females, metabolic disorders, particularly hypertension and diabetes, significantly increased this risk.
CONCLUSION: Fat-free mass index is a practical marker for low muscle mass screening. However, its accuracy varies by sex and metabolic health, requiring sex-and disease-specific calibration to improve malnutrition diagnosis and sarcopenia screening.