Developing and Validating an Age-Independent Equation of Multi-Frequency Bioelectrical Impedance Analysis for Estimation of Appendicular Skeletal Muscle Mass and Establishing Sarcopenia Cutoff

Abstract

Background: Appendicular skeletal muscle (or lean) mass (ALM) estimated by dualenergy X-ray absorptiometry (DXA) is considered to be a preferred method for sarcopenia studies. However, DXA is expensive, has limited portability, and requires radiation exposure. Bioelectrical impedance analysis (BIA) is inexpensive, easy to use, and portable; thus BIA might be useful in sarcopenia investigations. However, a large variety of models have been commercially supplied by different companies, and for most consumer products, the equations estimating ALM are not disclosed. It is therefore difficult to use these equations for research purposes. In particular, the BIA equation is often age-dependent, which leads to fundamental difficulty in examining age-related ALM loss. The aims of the current study were: 1) to develop and validate an equation to estimate ALM using multi-frequency BIA (MF-BIA) using theoretical models, and 2) to establish sarcopenia cutoff values using the equation for the Japanese population. The mean values minus 2 standard deviations of the skeletal muscle mass index (ALM/Ht 2 ) in these participants were 6.8 and 5.7 kg/m 2 in men and women, respectively. Conclusion: the current study established and validated a theoretical and age-independent equation using MF-BIA to estimate ALM and provided reasonable sarcopenia cutoff values.

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