Hemoglobin, lead exposure, and intelligence quotient: effect modification by the DRD2 Taq IA polymorphism
Ananya Roy1, Howard Hu, David C Bellinger
1Environmental and Occupational Health Sciences Institute, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA. aroykaushik@gmail.com
Environmental Health Perspectives
|January 6, 2011
Summary
The dopamine D2 receptor (DRD2) Taq IA polymorphism may worsen lead exposure's impact on children's IQ. This genetic factor appears to disrupt hemoglobin's protective effect on cognitive development, increasing vulnerability to lead-induced deficits.
Area of Science:
- Neuroscience
- Environmental Health
- Genetics
Background:
- Anemia and lead exposure are significant global public health concerns, frequently co-occurring.
- Animal studies indicate the dopamine D2 receptor (DRD2) influences cognition and behavior related to both lead and iron.
Purpose of the Study:
- To investigate if the DRD2 Taq IA polymorphism modifies the association between lead exposure, hemoglobin levels, and intelligence quotient (IQ) in children.
- To explore gene-environment interactions impacting child cognitive development.
Main Methods:
- Assessed blood lead and hemoglobin levels in 717 children (3-7 years) in Chennai, India.
- Determined IQ using Binet-Kamat scales and genotyped the DRD2 Taq IA polymorphism.
- Employed generalized estimating equations (GEEs) to analyze interactions between lead, hemoglobin, and DRD2 genotypes (homozygous variant vs. wild-type).
Main Results:
- In children with the homozygous DRD2 variant genotype, increased blood lead was associated with a greater IQ decrease (9 IQ points) compared to those with the wild-type allele (4 IQ points).
- Higher hemoglobin levels correlated with higher IQ in wild-type allele carriers.
- In homozygous variant children, increased hemoglobin was linked to a decrease in IQ (p=0.02 for interaction).
Conclusions:
- The DRD2 Taq IA polymorphism may impair the cognitive protective role of hemoglobin.
- This genetic variation may heighten children's susceptibility to IQ deficits resulting from lead exposure.
- Findings highlight the complex interplay between genetics, environmental toxins, and cognitive outcomes in children.
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