Estimation of segmental fat free mass in Taiwanese elderly females by bioelectrical impedance analysis with new mathematical model

Abstract

The aim of this study was to develop new predictive equations for evaluating the fat free mass (FFM) of body segments in Taiwan elderly female. Modified bioelectrical impedance analysis with eight electrodes (BIA₈) and referenced standard dual-energy x-ray absorptiometry (DXA) was applied to measure the segment body composition. The criterion of FFM values determined by DXA and predictive values by BIA were compared. After analyzing by linear regression, we obtained the FFM predictive equations by BIA₈ for segments. The Bland-Altman analysis was used to evaluate the differences of mean estimated segmental FFM from equations by BIA₈ and by DXA. The correlation coefficient (R) of FFM between values measured by DXA and estimated by BIA₈ in whole body, lower limbs, upper limbs and trunk were 0.89, 0.64, 0.60 and 0.81, respectively, and the differences of mean FFM were 2.39, 0.94, 0.27 and 2.02 kg, respectively. With the relatively higher weight coefficient of H²/Z (H, height; Z, impedance values), it plays a critical role in our new predictive equation. For the greater performance in prediction of fat free mass by our new BIA model, it provides potential in monitoring the body composition in female elderly by greater precision way.

Key words: Dual-energy x-ray absorptiometry (DXA), prediction equation, body composition.