Age and sex differences in childhood and adulthood obesity association with phthalates: Analyses of NHANES 2011–2014

Purpose: To examine the relationship between urinary phthalates and obesity in children/adolescents and in adults using data from NHANES 2011-2014. Methods: Using the National Health and Nutrition Examination Surveys (NHANES) 2011-2014, data files on ten urinary phthalates and obesity in children/adolescents (aged 6-19 years old) and in adults (20 years and older) were retrieved. Urinary phthalates were grouped as low molecular weight (LMW) phthalates, High Molecular Weight (HMW) phthalates, Di-2-ethylhexyl phthalates (DEHP) and categorized using weighted quartiles. Children/adolescents were classified as underweight/normal, overweight and obese using the BMI z-score. Adults were classified similarly using BMI measures of29.9, respectively. A multinomial logistic regression was conducted to determine the association of urinary phthalates and obesity while controlling for covariates. Participants with missing covariates, pregnant women and breastfeeding women were excluded. Results: Using multinomial logistic regression, the 3rd quartile for LMW and the 4th quartile for DEHP had statistically significant associations with being overweight in children/adolescents. The 3rd quartile for LMW was associated with being overweight in female children/adolescents and the 4th quartile for DEHP was associated with being overweight in male children/adolescents. The 4th quartile of individual phthalate MECPP was found to result in increased odds of being overweight in the female group and in children overall. The highest quartile for MEHHP was also significantly associated with obesity for children overall and for males. There were no statistically significant associations between urinary LMW, HMW and DEHP concentrations and obesity in adults, even when stratified by gender. Analyses of the individual phthalate components of LMW indicated an association between the 4th quartile of MnBP and overweight among female adults. No association was found in other individual phthalates and prevalence of obesity in adults. Conclusion: Urinary concentrations of LMW and DEHP are associated with increased rates of overweight in children/adolescents and there is a sex difference in this association. There is no apparent association between urinary phthalates and obesity in adults.