Assessment of appendicular skeletal muscle mass by bioimpedance in older community-dwelling Korean adults

It is crucial to investigate age-related body composition changes in geriatric medicine. Bioelectrical impedance analysis (BIA) is easy to perform, non-invasive, relatively inexpensive, and portable. However, the accuracy of measurement by BIA is questionable. To develop and cross-validate the predictive equation for estimated appendicular skeletal muscle mass (ASM) using BIA in older community-dwelling Korean adults, we include two cohorts: study participants aged 65–80 years in the Ansung cohort for the Korean Health and Genome Study (men, n = 285; women, n = 435) used as equation-generating group, and Korean Longitudinal Study of Health Aging (KLoSHA) as cross-validation group (men, n = 202; women, n = 208). Dual energy X-ray absorptiometry (DXA) and BIA were performed in both cohorts. Using multiple linear regression analysis, we drew a predictive equation for DXA-measured ASM by BIA resistance. From DXA and BIA measurements in the Ansung cohort, we generated the estimated equation ASM (kg) = [(Ht²/R × 0.104) + (age × −0.050) + (gender × 2.954) + (weight × 0.055)] + 5.663 where Ht is height in centimeters; R is BIA resistance in 250 Ω; for gender, men = 1 and women = 0; and age is in years. We validated this equation in the KLoSHA. The r² of the estimated ASM was 0.890. This BIA equation provides valid estimates of ASM in older Korean adults.