Associations between Cognitive Function, Blood Lead Concentration, and Nutrition among Children in the Central Philippines

Objective

Because little is known about its effects on cognitive function among children in less-developed countries, we determined the impact of lead exposure from other nutritional determinants of cognitive ability.

Study design

Data were from a cross-sectional population-based stratified random sample of 877 children (age 6 months-5 years) participating in the Quality Improvement Demonstration Study we are conducting in the Philippines. With data from validated psychometric instruments, venous blood samples, and comprehensive survey instruments, we developed multi-stage models to account for endogenous determinants of blood lead levels (BLLs) and exogenous confounders of the association between BLLs and cognitive function.

Results

A 1 μg/dL increase in BLL was associated with a 3.32 point decline in cognitive functioning in children aged 6 months to 3 years and a 2.47 point decline in children aged 3 to 5 years olds. BLL was inversely associated with hemoglobin and folate levels. Higher folate levels mitigated the negative association between BLL and cognitive function.

Conclusions

These population-based data suggest greater lead toxicity on cognitive function than previously reported. Our findings also suggest that folate and iron deficient children are more susceptible to the negative cognitive effects of lead. Folate supplementation may offer some protective effects against lead exposure.

Abbreviations: BLL, Blood lead level, BSID-II, Bayley Scales of Infant Development, second edition, FDA, US Food and Drug Administration, HOME, Home observation for measurement of the environment, MDI, Mental development index, NHANES, National Health and Nutrition Examination Survey, NIH, US National Institutes of Health, PDI, Psychomotor development index, PIQ, Performance intelligence quotient, PP, Philippine pesos, QIDS, Quality improvement demonstration study, VIQ, Verbal intelligence quotient, WPPSI-III, Wechsler Preschool and Primary Scales of Intelligence, third edition