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Bioelectrical impedance for measuring percentage body fat in young persons with Down syndrome: validation with dual-energy absorptiometry


S Loveday, M.B., Ch.B., Department of Paediatrics, Child and Youth Health, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
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Aim:  Children with Down syndrome have an increased prevalence of obesity, although there is little work describing body composition in this population. The aims of this study were to accurately measure body fat in children with Down syndrome and to identify which existing algorithm best predicts percentage body fat in this population.

Methods:  Seventy children with Down syndrome had anthropometric, bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) data collected to calculate percentage body fat (PBF). Pearson correlations were carried out to assess the relationships of various methods for measuring body fat and Bland–Altman plots to assess systematic error.

Results:  Mean PBF was 30.5% for girls and 22.5% for boys. A total of 38% of girls and 23% of boys were obese according to international criteria. PBF as determined by DXA correlated well with PBF by BIA in both girls and boys (r = 0.91 and 0.89, respectively, p < 0.001).

Conclusion:  There are high rates of obesity in children with Down syndrome. BIA can be used to accurately determine adiposity in this population. We recommend the use of the Schaeffer algorithm for calculation of PBF in children with Down syndrome.