Image: CC/Edgar181. BPA compund.
Key study points:
1. Increasing urinary BPA is associated with a higher risk of obesity in children.
2. This association was significant for white children when stratified by race.
3. Causality cannot be drawn from this study and other explanations for the association are plausible.
Primer: 93% of the U.S. population has detectable levels of Bisphenol A (BPA) in urine, and studies show that 99% of urine BPA comes from food sources/packaging. BPA has also been shown to accumulate in human fat, where it is thought to disrupt several metabolic processes. Because of this, researchers are exploring the possible link between BPA and obesity. Accordingly, BPA has been associated with an increased risk of obesity in adults as well as diabetes and cardiovascular disease. Given the sensitivity of children to metabolic disruptions, the authors of this study sought to analyze BPA concentrations and body mass index (BMI) in children/teens – a population with little data on the matter.
This [cross-sectional] study: Authors sourced data from the well-known NHANES trial (US population), focusing on lab values (urine BPA), diet, physical examination components. They used standardized BMI z scores to adjust BMI for age and sex, categorizing overweight individuals as those with a BMI >85%ile for age and sex and obese as >95%ile for age and sex. 2838 participants (ages 6-19) were included in the final analysis. They key outcome of interest was adjusted BMI. The proportion of overweigh and obese subjects (34.1% and 17.8%, respectively) was in-line with other NHANES derived reports. The authors split urine BPA concentrations in quartiles, and found that those falling in the second, third and fourth quartiles had the highest odds of obesity (odd ratio [OR] 2.22, 2.09, 2.53, respectively; p<.001 for all). After stratifying the data further, it was demonstrated that the association was only significant for whites, but not Hispanic or non-Hispanic black children. For white children, the estimated prevalence of obesity, sorted by increasing BPA quartile, was 4.7%, 17.5%. 17.1% and 22.8% (p<.001 for all).
In sum: This is the first study showing a link between an environmental exposure and obesity in children dervied from a generalizable national sample. Note that the authors adjusted for numerous variables including age, sex, race, caloric intake, urinary creatinine and more. These results are also in accordance with previous findings in the adult population. Clearly, in a cross-sectional study one cannot infer causality, and it is quite possible that the relationship is reflected in the greater consumption of food in overweight children, perhaps varied in the types of food by race. Though data were adjusted for caloric intake, the sources of these calories may still differ between the obese and non-obese subjects. More research is needed in the area and in this specific sub-population to establish a more concrete link.
Written by M.S.
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