IQ and Blood Lead Levels: Effect Modification By ALAD Amongst Children in Chennai, India

Abstract

PP-31-171 Background/Aims: Exposure to lead is known to be causally associated with deficits in intelligence quotient (IQ) among children. However, little is known about genetic factors that affect neurocognitive susceptibility to lead. The effect of lead on the body has been known to vary across the aminolevulinate delta-dehydratase (ALAD) genotype among adults, but there are few studies examining the association in children. This study tests the hypothesis that the ALAD polymorphism modifies the association between lead and IQ among school-age children in Chennai, India. Methods: A total of 756 children, aged 3 to 7 years, were recruited from 12 schools in Chennai, India. Blood lead levels (BLL) were measured using the LeadCare Analyzer. The Binet–Kamat intelligence test was administered to ascertain IQ. ALAD genotype, for 695 children, was determined using the MassARRAY iPLEXTM. Stratified and interaction generalized linear models were used to explore modification of the lead and IQ association by ALAD genotype (1/1 vs. 1/2 + 2/2 genotypes) after adjusting for age, socioeconomic status, mother's and father's education, and hemoglobin. Results: The distribution of the ALAD 1/1, ALAD 1/2, and ALAD 2/2 genotype in this population was 73.4%, 23.2%, and 3.4%, respectively. The mean BLL for the whole population was 11.5 μg/dL. Children with the ALAD 1/1 genotype experienced a 3.11 reduction in IQ points with every 10 μg/dL increase in blood lead levels (P = 0.022). Children with the ALAD 1/2 or 2/2 genotype experienced a 1.72 drop in IQ points with every 10 μg/dL increase in BLLs (P = 0.4603). In the interaction model, IQ decreased by 0.698 points between the ALAD groups, with every 10 μg/dL increase in blood lead levels (P = 0.788). Conclusion: This study did not find significant effect modification of the lead and IQ association by ALAD genotype.