Association between phthalates and attention deficit disorder and learning disability in U.S. children, 6-15 years

Environ Res. 2014 Jan;128:64-9. doi: 10.1016/j.envres.2013.10.004. Epub 2013 Nov 19.

Abstract

Objective: This study investigates the association between urinary phthalate metabolite levels and attention deficit disorder (ADD), learning disability (LD), and co-occurrence of ADD and LD in 6-15-year-old children.

Methods: We used cross-sectional data from the National Health and Nutrition Examination Survey (NHANES, 2001-2004). Phthalate metabolites with ≥75% detection in urine samples were examined. The study population comprised 1493 children with parent-reported information on ADD or LD diagnosis and phthalate concentrations in urine. Phthalate concentrations were creatinine-adjusted and log10-transformed for analysis. All models controlled for child sex, age, race, household income, blood lead, and maternal smoking during pregnancy.

Results: There were 112 ADD cases, 173 LD cases, and 56 ADD and LD cases in the sample. After adjusting for potential confounders, we found increased odds of ADD with increasing urinary concentration of di-2-ethylhexyl phthalates (OR: 2.1; 95% CI: 1.1, 3.9) and high molecular weight phthalates (OR: 2.7; 95% CI: 1.2, 6.1). In addition, dibutyl phthalates (OR: 3.3; 95% CI: 0.9, 12.7) and high molecular weight phthalates (OR: 3.7; 95% CI: 0.9, 14.8) were marginally associated with increased odds of co-occurring ADD and LD. We did not find associations for any phthalate and LD alone. We observed stronger associations between phthalates and ADD and both ADD and LD in girls than boys in some models.

Conclusions: We found cross-sectional evidence that certain phthalates are associated with increased odds of ADD and both ADD and LD. Further investigations with longitudinal data are needed to confirm these results.

Keywords: ADD; ADHD; Attention deficit disorder; CDC; CI; Centers for Disease Control and Prevention; DBP; DEHP; DSM-IV; Diagnostic and Statistical Manual of Mental Disorders: Fourth Edition; High M.W; LD; LOD; Learning disability; Low M.W; MBzP; MCPP; MEP; NHANES; National Health and Nutrition Examination Survey; OR; PIR; Phthalates; Plasticizers; attention deficit disorder; attention-deficit/hyperactivity disorder; confidence interval; di-2-ethylhexyl phthalate; dibutyl phthalate; high molecular weight; learning disability; limit of detection; low molecular weight; mono-(3-carboxypropyl) phthalate; mono-benzyl phthalate; mono-ethyl phthalate; odds ratio; poverty income ratio.

MeSH terms

  • Adolescent
  • Attention Deficit Disorder with Hyperactivity / chemically induced*
  • Attention Deficit Disorder with Hyperactivity / epidemiology
  • Attention Deficit Disorder with Hyperactivity / urine
  • Child
  • Comorbidity
  • Cross-Sectional Studies
  • Female
  • Humans
  • Learning Disabilities / chemically induced*
  • Learning Disabilities / epidemiology
  • Learning Disabilities / urine
  • Male
  • Nutrition Surveys
  • Phthalic Acids / adverse effects*
  • Phthalic Acids / urine
  • United States / epidemiology

Substances

  • Phthalic Acids