245 - Examining the associations of child lead and prenatal folate with child IQ in the HOME (Health Outcomes and Measurements of the Environment) Study

Poster Number: 245
Publication Number: 245.1209

Background: Prenatal and early life exposure to environmental toxicants is associated with worse neurocognitive outcomes in children. This includes exposure to lead and tobacco smoke, two prevalent toxicants in the United States. Preliminary studies suggest folate may mitigate other environmental exposures via oxidative pathways.

Objective: We examined the association between child lead at 12 months and child IQ at ages 5-12 years, while adjusting for prenatal tobacco smoke exposure. We then studied whether prenatal total folate modifies the association between child lead and IQ.

Design/Methods: Complete data were available for 199 mother-child dyads. Child whole blood lead was assessed at age 12 months. Average prenatal cotinine (a biomarker of tobacco smoke) was calculated from maternal serum concentrations at 16 and 26 weeks gestation. Prenatal total folate was measured in maternal serum at 16 weeks or delivery. Child IQ was assessed via WISC at age 8-12, or via WPPSI at age 5 years if WISC data was not available. For both assessments, age-adjusted, full-scale scores were included. Multivariable linear regression models were used, adjusting for maternal education, household income, prenatal serum cotinine, prenatal vitamin use, and child sex.

Results: In bivariate linear models, child lead was negatively associated with child IQ (estimate for each doubling of blood lead = -4.6; 95% Confidence Interval (CI): [-6.8, -2.3]) and prenatal total folate was positively associated with child IQ (estimate for each doubling of total folate = 0.02; 95% CI: [0.01, 0.02]). The associations between child lead at age 12 months, prenatal total folate, and child IQ were not significant. Furthermore, there was no significant interaction between child lead and prenatal folate.

Conclusion(s): Our study suggests the association between child blood lead level at age 12 months and child IQ is heavily confounded by maternal education or other correlated sociodemographic variables. Additionally, maternal total folate was a significant predictor of child IQ when adjusting for maternal education, but there was no interaction of folate with child lead. Further studies investigating early toxic and sociodemographic mediators of child IQ are necessary. While the detrimental effects of child lead exposure on neurodevelopment have been illustrated extensively, this study suggests that other sociodemographic factors ought to be considered in addition to lead exposure when assessing cognitive outcomes.