Urinary concentrations of bisphenol A and phthalate metabolites and weight change: a prospective investigation in US women

Abstract

Both bisphenol A (BPA) and phthalates are known endocrine-disrupting chemicals for which there is widespread general population exposure. Human exposure occurs through dietary and non-dietary routes. Although animal studies have suggested a potential role of these chemicals in obesity, evidence from human studies is sparse and inconsistent, and prospective evidence is lacking. This study evaluated urinary concentrations of BPA and major phthalate metabolites in relation to prospective weight change. The study population was from the controls in a prospective case-control study of type 2 diabetes in the Nurses' Health Study (NHS) and NHSII. A total of 977 participants provided first-morning-void urine samples in 1996-2002. Urinary concentrations of BPA and nine phthalate metabolites were measured using liquid chromatography-mass spectrometry. Body weights were self-reported at baseline and updated biennially thereafter for 10 years. On average, the women gained 2.09 kg (95% confidence interval (CI), -2.27 to 6.80 kg) during the 10-year follow-up. In multivariate analysis with adjustment of lifestyle and dietary factors, in comparison with women in the lowest quartile of BPA concentration, those in the highest quartile had 0.23 kg per year (95% CI, 0.07-0.38 kg per year) greater weight gain during the 10-year follow-up (P-trend=0.02). Several phthalate metabolites, including phthalic acid, MBzP and monobutyl phthalate, were also associated with faster prospective weight gain in a dose-response fashion (P-trend<0.01), whereas other phthalates metabolites, including MEP and monoethylhexyl phthalate, were not monotonically associated with body weight change. These data suggest urinary concentrations of BPA and certain individual phthalate metabolites that were associated with modestly greater weight gain in a dose-response fashion. These data are consistent with a potential role of BPA and phthalates in obesity, although more prospective data are needed to corroborate these observations.