Childhood polybrominated diphenyl ether (PBDE) serum concentration and reading ability at ages 5 and 8 years: The HOME Study

Abstract

Background: Polybrominated diphenyl ethers (PBDEs) exist extensively in the environment and human beings. PBDE concentrations are higher in children than adults. A previous study found that prenatal PBDE exposure was associated with decreased reading skills in children; however, evidence is limited on the potential impact of childhood exposure to PBDEs. The study examined the association between childhood PBDE exposures and reading ability in children at ages 5 and 8 years.

Methods: The study included 230 children from an ongoing prospective pregnancy and birth cohort study, the Health Outcomes and Measures of Environment (HOME) Study, conducted in Cincinnati, Ohio. Children's serum concentrations of eleven PBDE congeners were measured at 1, 2, 3, 5, and 8 years. The Woodcock-Johnson Tests of Achievement - III and the Wide Range Achievement Test - 4 were administered to assess children's reading skills at ages 5 and 8 years, respectively. We used multiple informant models to examine the associations between repeated measures of PBDEs and reading scores at ages 5 and 8 years. We also estimated the βs and 95% CIs of the association of PBDE measure at each age by including interaction terms between PBDE concentrations and child age in the models.

Results: All childhood BDE-153 concentrations were inversely associated with reading scores at 5 and 8 years, but associations were not statistically significant after covariate adjustment. For example, a 10-fold increase in BDE-153 concentrations at ages 3 and 5 years was associated with a -5.0 (95% confidence interval (CI): -11.0, 1.0) and -5.5 (95% CI: -12.5, 1.4) point change in Basic Reading score at age 5 years, respectively. Similarly, the estimates for Brief Reading score at age 5 years were -4.5 (95% CI: -10.5, 1.5) and -5.2 (95% CI: -12.2, 1.7) point changes, respectively. Serum concentration of BDE-47, -99, -100, and Sum₄PBDEs (sum of BDE-47, 99, 100, and 153) at every age were inversely associated with reading scores at ages 5 and 8 years in unadjusted analyses. While the adjusted estimates were much attenuated and became non-significant, the direction of most of the associations was not altered.

Conclusion: Our study has shown a suggestive but non-significant trend of inverse associations between childhood PBDE serum concentrations, particularly BDE-153, and children's reading skills. Future studies with a larger sample size are needed to examine these associations.

Keywords: Childhood; Polybrominated diphenyl ethers; Reading ability; Serum concentration.

Figure 1.

Estimated score differences and 95% CIs in WJ-III reading scores at age 5 years (a, n=185) and WRAT-4 Reading Composite scores at age 8 years (b, n=199) by a 10-fold increase in childhood serum BDE-153 concentrations using the imputed datasets. Adjusted for maternal age, education, race, IQ, household income, parity, marital status, maternal serum cotinine, maternal depression, child sex, and HOME score in multiple informant models.

Figure 2.

Scatter plots of childhood serum BDE-153 concentrations and WJ-III reading scores at age 5 years with Generalized Additive Model curve fitting using the non-imputed, original dataset. (A.) Basic Reading score at 5 years (n=153); (B.) Brief Reading score at 5 years (n=154). Data points represent serum BDE-153 concentrations at age 5 years and corresponding reading score for each child. Solid lines indicate the natural cubic spline regression of the association after adjustment for maternal age, education, race, IQ, household income, parity, marital status, maternal serum cotinine, maternal depression, child sex, and HOME score. Dotted lines are 95% confidence intervals of the regression curve.