Sex-specific screening of low appendicular skeletal muscle mass index in community dwelling adults: A descriptive...

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.

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.

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.

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.