Comparison of three BIA muscle indices for sarcopenia screening in old adults

Purpose: In response to the inconsistent cutoff points for the diagnosis of low muscle mass in elderly, the study endeavored to establish a preferred norm for sarcopenia screening by comparing three muscle indices with physical functional assessment. Methods: One thousand healthy adults aged 20-40 were recruited for body composition assessment using bioelectric impedance analysis (BIA, Tanita BC-418, Japan) with segmental measures during annual health examination. Additionally, 308 elderly ambulatory outpatients recruited for comprehensive geriatric assessment were assessed for muscle strength, physical performance, and body composition using the same BIA device. Results: With the definition of low muscle mass set at 2 standard deviations below the mean value of appendicular skeletal muscle index (ASMI, appendicular skeletal muscle mass/height(2)) in the young reference groups, the cutoff points for men and women were 6.76 and 5.28 kg/m(2), respectively. The ratios of low muscle mass in the elderly subjects read 8.5% for men and 13.5% for women. The cutoff points of the other two muscle indices - total skeletal muscle index (total skeletal muscle mass/height2, TSMI), and skeletal muscle index (ASM/total body weight, SMI) - were also calculated and the ratios of low muscle mass appeared to be 25.6% and 69.8%, respectively. Compared to their compartments, the elderly with low muscle mass defined by ASMI were older and demonstrated a higher proportion of physical frailty, lower body mass index, lower muscle strength, and poorer physical performance. Conclusions: Compared with TSMI and SMI, ASMI might serve as a preferred index for the diagnosis of low muscle mass. (C) 2013 Elsevier Masson SAS and European Union Geriatric Medicine Society. All rights reserved.