Declining Blood Lead Levels and Cognitive Changes in Moderately Lead-Poisoned Children

Abstract

OBJECTIVE: To determine whether chelation therapy or biochemical changes during a lead-lowering intervention was associated with changes in cognitive functioning of moderately lead-poisoned children. It was hypothesized that cognitive performance would improve as blood lead level declined over time. DESIGN: Short-term intervention study with measures obtained before and after intervention. SETTING: Hospital specialty clinic and university research center. PATIENTS: A total of 154 previously untreated children referred to clinic with blood lead levels between 1.21 and 2.66 mumol/L (25 and 55 micrograms/dL) at time of enrollment. Ages ranged from 13 to 87 months. INTERVENTION: Enrolled children were treated with edetate calcium disodium (EDTA) if eligible and/or with orally administered iron supplement if iron deficient. For all children, housing inspections and abatement procedures were performed as necessary. MAIN OUTCOME MEASURES: Score on Bayley Mental Development Scale or Stanford-Binet Intelligence Scale (4th edition). RESULTS: There was no effect of edetate calcium disodium treatment per se. In the short term (7 weeks), changes in blood lead levels were not related to changes in cognitive scores. In the long term (6 months), however, changes in performance were significantly related to changes in blood lead level, even after controlling for confounding variables. The standardized score increased 1 point for every decrease of 0.14 mumol/L (3 micrograms/dL) in blood lead level. CONCLUSION: The results suggest an association between decreases in blood lead level and cognitive improvements in moderately lead-poisoned children.