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Assessing windows of susceptibility to lead-induced cognitive deficits in Mexican children
Joe M Braun1, Elaine Hoffman, Joel Schwartz
1Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. jbraun@hsph.harvard.edu
Insights
Lead exposure at age 2 significantly impacts children's cognitive development. Higher blood lead (Pb) levels at this age predict lower cognitive scores, highlighting critical windows for childhood Pb prevention strategies.
Area of Science:
- Environmental Health
- Neuroscience
- Pediatrics
Background:
- Identifying critical periods for lead (Pb) exposure and its impact on child cognitive development is crucial.
- Previous research has not clearly defined susceptible windows for Pb-induced cognitive decrements.
Purpose of the Study:
- To determine specific windows of susceptibility to lead exposure by examining the relationship between serial blood lead (Pb) concentrations and cognitive abilities in children.
- To analyze data from 1035 mother-child pairs in Mexico City birth cohorts.
Main Methods:
- Longitudinal blood lead (Pb) measurements were collected from children at ages 1, 2, 3, and 4 years.
- Child cognitive abilities were assessed at age 4 using the General Cognitive Index (GCI) of the McCarthy Scales of Children's Abilities.
- Multivariable linear regression was employed to analyze the association between blood lead (Pb) levels and GCI scores, adjusting for potential confounders.
Main Results:
- Blood lead (Pb) concentrations at 2 years of age showed the strongest association with reduced GCI scores at 4 years (β: -3.8; 95% CI: -6.3, -1.4).
- Mutual adjustment for other blood lead (Pb) measurements indicated a stronger association at 2 years (β: -7.1; 95% CI: -12, -2.0).
- Associations varied across cohorts, suggesting potential exposure, outcome, or cohort-specific factors.
Conclusions:
- Higher blood lead (Pb) levels at 2 years of age were most predictive of decreased cognitive abilities in this cohort.
- These findings can inform the development of targeted childhood lead (Pb) prevention strategies in developing countries.
Background:
The identification of susceptible periods to Pb-induced decrements in childhood cognitive abilities remains elusive.
Objective:
To draw inferences about windows of susceptibility using the pattern of associations between serial childhood blood lead (BPb) concentrations and children's cognitive abilities at 4 years of age among 1035 mother-child pairs enrolled in 4 prospective birth cohorts from Mexico City.
Methods:
Multiple longitudinally collected BPb measurements were obtained from children (1, 2, 3, and 4 years) between 1994 and 2007. Child cognitive abilities were assessed at 4 years using the general cognitive index (GCI) of the McCarthy Scales of Children's Abilities. We used multivariable linear regression to estimate the change in cognitive abilities at 4 years of age with a 10 μg/dL increase in childhood BPb concentrations adjusting for maternal IQ, education, marital status, child sex, breastfeeding duration, and cohort.
Results:
In separate models for each BPb measurement, 2 year BPb concentrations were most strongly associated with reduced GCI scores at 4 years after adjusting for confounders (β: -3.8; 95% confidence interval CI: -6.3, -1.4). Mutual adjustment for other BPb concentrations in a single model resulted in larger, but less precise estimate between 2 year BPb concentrations and GCI scores at 4 years of age (β: -7.1; 95% CI: -12, -2.0). The association between 2 year BPb and GCI was not heterogeneous (p=0.89), but some BPb and GCI associations varied in magnitude and direction across the cohorts. Additional adjustment for child hemoglobin, birth weight, gestational age, gestational BPb concentrations, or test examiner did not change the pattern of associations.
Conclusions:
Higher BPb concentrations at 2 years of age were most predictive of decreased cognitive abilities among these Mexico City children; however, the observed pattern may be due to exposure, outcome, or cohort related factors. These results may help developing countries more efficiently implement childhood Pb prevention strategies.
