Urinary Phthalate Metabolite Levels In Association With Attention-Deficit Hyperactivity Disorder In Children: A Community Based Case - Control Study

Phthalates is endocrine disrupting chemicals used extensively to manufacture plastics and PVC resin liners. Previous animal studies showed that the phthalate compounds might cause hyperactivity and impulsivity in rats. The purpose of this study is to investigate a possible association between urinary phthalate metabolite levels and ADHD in Children. Based on a community survey for ADHD screening using the Korean version of ADHD rating scale in elementary schools of Cheonan, city, a case control study was designed to examine associations with environmental risk factors for ADHD. Cases and controls were confirmed by a pediatric psychiatrist through a clinical work-up. Controls were selected by individual school-grade and gender matching with the cases. A total of 219 cases and 219 controls aged 6-10 were included in the study. Children's urine samples for 3 phthalate metabolites assessment were collected. Questionnaire administration to obtain information on general characteristics, socio demographic and various confounders were done at the time of participants' hospital visits. Analysis was performed using a conditional logistic regression model adjusted for confounders and covariates. Cases were lower in their mother's education level, more exposed to SHS during pregnancy and childhood than controls. Geometric means(geometric standard deviation) levels of urinary phthalates, mono-2-ethyl-5-hydroxyhexyl phthalate (5-OH-MEHP), mono-2-ethyl-5-oxohexyl phthalate (5-OX-MNHP), and mono-n-butyl phthalate (MnBP), were 45.07 (2.13) and 46.84 (2.12), 30.69 (2.21) and 32.46 (2.18), and 82.20 (2.14) and 82.48 (2.24) ppb in cases and controls, respectively. The risk of ADHD increased significantly according to increase of 5-OH-MEHP levels (ppb/creatinine) in all children and boys. MnBP also showed a significant positive association with risk of ADHD in all, boys and girls. The present study suggests an significant association between phthalate exposure and ADHD risk in children.