Estimating body composition in children with Duchenne muscular dystrophy: comparison of bioelectrical impedance analysis and skinfold-thickness measurement

BACKGROUND: Duchenne muscular dystrophy (DMD) is often associated with obesity, which worsens the handicap early in the course of the disease. Nutritional assessment, however, can be difficult and often misleading in DMD. OBJECTIVE: Two methods of estimating body composition in DMD, skinfold-thickness (ST) measurement and bioelectrical impedance analysis (BIA), were compared with a reference method, labeled water dilution (WD). DESIGN: Body composition was estimated by using ST measurements and BIA (50 kHz, 800 mAmp), as well as the WD method (1 mL H2(18)O/kg) in 11 DMD patients with a mean (+/-SD) age of 10.0 +/- 2.5 y. RESULTS: When compared with the WD method, ST measurement significantly (P < 0.01) overestimated fat-free mass (FFM) (mean +/- SD ST: 24.5 +/- 5.9 kg; mean +/- SD WD: 18.2 +/- 2.5 kg), which led to an underestimation of the percentage of fat mass (%FM) (ST: 23.3 +/- 10.4%; WD: 40.1 +/- 17.1%; P < 0.05). In contrast, estimates obtained with BIA (FFM: 21.5 +/- 4.5 kg; %FM: 31.3 +/- 13.9%) did not differ from those obtained with WD. The difference from the reference method was less for BIA (mean: 3.3 kg; 95% CI: 0.8, 4.9 kg) than for ST (6.3 kg; 2.2, 8.6 kg). WD and BIA defined 73% and 55%, respectively, of the children as obese (%FM associated with body mass index cutoffs for obesity), whereas ST measurements defined 9% as obese (P < 0.01). CONCLUSIONS: Body-composition estimates by BIA are closer to those by WD than are those by ST measurement. Early detection of fat accumulation and longitudinal monitoring of nutritional care are 2 relevant applications of BIA to prevent obesity and hence lessen the burden of DMD.