Comparison on two algorithms of skeletal muscle mass index: an observational study in 141,451 Chinese adults

Abstract Background/AimsThere were two methods used for measuring skeletal muscle mass index (SMI); one is SMM (%) = skeletal muscle mass(kg) /body weight mass (kg)×100%, and the other is SMH (kg/m2) = skeletal muscle mass(kg)/ height (m)2. The aim of this study was to compare on the distribution of the two algorithms of SMI.MethodsThis study included 141,451 participants who accepted physical examination. Body mass index (BMI), and body fat percentage (BFP) were estimated using a bioelectrical impedance analyzer. SMI was calculated by the two algorithms.ResultsLevels of BMI, BFP, SMM and SMH differed significantly among the sexes. BMI and BFP were significantly positively correlated with age, while SMM was significantly negatively correlated with age (β = -0.23, P < .001). There was no significant correlation between SMH and age. Furthermore, there was a negative correlation between SMM and BMI (β = -0.53, P < .001), and a positive correlation between SMH and BMI (β = 0.79, P < .001). Both SMM (β= -0.98, P < .001) and SMH (β = -0.0642, P < .001) were negatively correlated with BFP. Nevertheless, the correlation coefficient of the former was significantly greater than that of the latter. In gender stratification, SMM maintained the analogous correlation, while the correlation between SMH and other indicators changed. SMM showed a gradual downward trend, but SMH and BFP showed a gradual upward trend from low body weight to grade Ⅲ obesity.ConclusionsSMM may be a more ideal algorithm for reflecting SMI, compared to SMH.