Abstract
Aim: To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults. Research design: A cross-sectional study was carried out. Subjects: Sixty-eight females and 42 males aged 21-82 years participated in the study. Methods: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance ( R ) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs. Results: The resistance index (RI), i.e. the height 2 /resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM ( vs 0.57), 45% more variance of LTM arm ( vs 0.48) and 36% more variance of LTM leg ( vs 0.50) ( p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI 2 sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM arm and LTM leg. Conclusion: Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.
Highlights
Sarcopenia, i.e. a decrease in skeletal muscle mass (SMM) and strength, is a common feature of ageing (Roubenoff 2000)
Dual-energy X-ray absorptiometry (DXA) compares well with computed tomography (CT) and magnetic resonance imaging (MRI) and has been proposed for the assessment of SMM owing to its lower cost and higher availability (Fuller et al 1999a, 2002, Visser et al 1999, Wang et al 1999a; Elia et al 2000, Levine 2000, Shih et al 2000)
lean tissue mass (LTM) is synonymous with SMM so that DXA provides a simple means of estimating SMM (Wang et al 1999a)
Summary
Sarcopenia, i.e. a decrease in skeletal muscle mass (SMM) and strength, is a common feature of ageing (Roubenoff 2000). Sarcopenia may impair the ability of the body to cope with stress and disease and contribute to morbidity and mortality in the elderly (Dutta 1997). The prevalence of sarcopenia is not known and this is of obstacle to the understanding of its prognostic significance (Dutta 1997). The reference methods for the assessment of SMM are computed tomography (CT) and magnetic resonance imaging (MRI) (Lukaski 1996). Dual-energy X-ray absorptiometry (DXA) compares well with CT and MRI and has been proposed for the assessment of SMM owing to its lower cost and higher availability (Fuller et al 1999a , 2002, Visser et al 1999, Wang et al 1999a; Elia et al 2000, Levine 2000, Shih et al 2000). A limitation of DXA is, Annals of Human Biology ISSN 0301–4460 print/ISSN 1464–5033 online # 2003 Taylor & Francis Ltd http://www.tandf.co.uk/journals
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