Environment-wide association study on childhood obesity in the U.S.

Background: Childhood obesity is a national public health issue with increasing prevalence. It has been linked to diet, lack of physical activity, and genetic susceptibility, with more recent evidence that it could also result from environmental factors. Studies linking it to environmental factors are limited, unsystematic, incomprehensive, and inconclusive.
Objective: To conduct an environment-wide association study (EWAS) to comprehensively investigate all the environmental factors available in a nationally representative sample of children to determine factors associated with childhood obesity.
Methods: We utilized the 1999-2016 National Health and Nutrition Examination Survey (NHANES) datasets and included all children/adolescents (6-17 years). Obesity was measured using body mass index and waist to height ratio. A multinomial and binary logistic regression were used adjusting for age, sex, race/ethnicity, creatinine, calorie intake, physical activity, screen time, limitation to physical activities, and socioeconomic status. We then controlled for multiple hypothesis testing and validated our findings on a different cohort of children.
Results: We found that metals such as beryllium (OR: 3.305 CI: 1.460-7.479) and platinum (OR: 1.346 CI: 1.107-1.636); vitamins such as gamma-tocopherol (OR: 8.297 CI: 5.683-12.114) and delta-tocopherol (OR: 1.841 CI:1.476-2.297); heterocyclic aromatic amines such as 2-Amino-9H-pyrido (2,3-b) indole (OR: 1.323 CI: 1.083-1.617) and 2-Amino-3-methyl-9H-pyriodo(2,3-b)indole (OR: 2.799 CI: 1.442-5.433); polycyclic aromatic amines such as 9- fluorene (OR: 1.509 CI: 1.230-1.851) and 4-phenanthrene (OR: 2.828 CI: 1.632-4.899); and caffeine metabolites such as 1,3,7-trimethyluric acid (OR: 1.22 CI: 1.029-1.414) and 1,3,7-trimethylxanthine (OR: 1.258 CI: 1.075-1.473) were positively and significantly associated with childhood obesity.
Conclusion: Following the unique concept of EWAS, certain environmental factors were associated with childhood obesity. Further studies are required to confirm these associations while investigating their mechanisms of action.
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