Gender differences in the associations between urinary bisphenol a and body composition among American children: The national health and nutrition examination survey, 2003-2006

Background: As an endocrine disruptor, bisphenol A (BPA) exposure has been implicated as a potential risk factor in childhood obesity, which is defined using percentiles of body mass index for age. We aimed to examine the associations between BPA exposure, reflected by urinary BPA concentration, and body composition in American children. Methods: Data of 1860 children aged 8-19 years who participated in the 2003-2006 National Health and Nutrition Examination Survey (NHANES) were analyzed in this study. Urinary BPA concentration (ng/mL) was used to indicate BPA status in the body. Body composition was measured by dual-energy X-ray absorptiometry (DXA). Multivariate linear regression models were fitted using survey procedures to investigate the associations between urinary BPA level and body composition separately for boys and girls. Results: After adjusting for demographic and lifestyle covariates, higher quartiled and log-transformed urinary BPA levels were significantly associated with elevated lean body mass index (LBMI) z-scores in boys (p < 0.05), and significantly associated with elevated fat mass index (FMI) z-scores in girls (p < 0.05). Lower urinary BPA concentration was associated with lower percentage of trunk fat in girls (compared to 1st quartile, 2nd-quartile: B = 2.85, 95% CI, 0.92-4.78; 3rd-quartile: B = 2.57, 95% CI, 0.28-4.85; 4th- quartile: B = 2.79, 95% CI, 0.44-5.14; all p < 0.05). Such patterns were not observed in boys. Conclusions: Higher BPA levels may be associated with elevated LBM in boys, but not in girls, while higher BPA levels may be associated with elevated FM in girls, but not in boys.