Body composition of neonates from fan beam dual energy X-ray absorptiometry measurement

Abstract

BACKGROUND: Fan beam dual energy x-ray absorptiometry (FB DXA) has recently been validated for the measurement of body composition in small subjects. This study represents the first report of body composition (bone mineral content, fat mass, and lean mass) in human neonates measured by FB DXA. METHODS: FB DXA measurements were performed in 73 healthy singleton neonates with mean +/- SD birth weights 3354 +/- 316 g (range, 2720 to 3982 g) and gestational ages 39.5 +/- 1.2 weeks (range, 37 to 42 weeks). There were 26 white (11 male infants, 15 female infants), 42 African American (17 male infants, 25 female infants), and 5 Hispanic (4 male infants, 1 female infant) infants. The predictive ability of physiologic parameters to predict body composition measurements was determined with regression analysis. RESULTS: The mean +/- SD for bone mineral content was 89.3 +/- 14.1 g, fat mass was 485 +/- 14.1 g, and lean mass was 2898 +/- 281.5 g. Weight was significantly correlated with all DXA measurements and was the single best predictor of body composition. Weight alone contributed 32% to 98% of the variance of the DXA measured parameters. Gender, race, and length were additional predictors that could be forced into a predictive equation for selected DXA dependent variables according to statistical significance. An independent gender effect was also demonstrated, with male infants having higher lean mass but lower fat mass. CONCLUSIONS: Our data in human neonates demonstrated the ability of FB DXA to measure body composition. Body weight is the best physiologic predictor of overall body composition. There is also an independent gender effect on soft tissue body composition.

This is the first report on body composition of human neonates measured by fan beam dual energy absorptiometry. Body weight (vs length, race, and gender) is the dominant physiologic predictor of body composition. There is also an independent gender effect, with male neonates having higher lean mass and lower fat mass.