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Low-Level Lead Exposure, Intelligence and Academic Achievement: A Long-term Follow-up Study
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1992
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NeuropsychologyEducational PsychologyLow-level Lead ExposureEducationSocial SciencesPsychologyLead PoisoningIntellectual ImpairmentAcademic PerformanceCognitive DevelopmentUnderachieving ChildEarly Life ExposureNeuropsychological FunctioningLead ExposureCognitive VariableLong-term Follow-up StudyCognitive FunctionEducational LeadershipChild DevelopmentCognitive PerformancePediatricsAcademic Achievement
Low‑level lead exposure’s impact on children’s intellectual and academic performance at school age remains uncertain. The study prospectively examined whether early childhood lead exposure predicts later cognitive and academic outcomes in middle‑class and upper‑middle‑class children. Neuropsychological testing at age 10, including the WISC‑R and K‑TEA, was administered to 148 children whose lead exposure had been measured repeatedly from infancy through 24 months. Higher blood lead at 24 months, but not earlier, was significantly linked to lower WISC‑R Full‑Scale IQ (≈5.8‑point decline per 10 µg/dL) and lower K‑TEA scores (≈8.9‑point decline), indicating that modest lead exposure at 24 months predicts intellectual and academic deficits at age 10.
The implications of low-level lead exposure for children's intellectual and academic performance at school age are uncertain. This issue was investigated in a prospective study of middle-class and upper-middle-class children with low lifetime exposures to lead. A battery of neuropsychological tests was administered at age 10 years to 148 children whose lead exposure and cognitive function had been previously assessed at ages 6, 12, 18, 24, and 57 months. Primary endpoints were Wechsler Intelligence Scale for Children-Revised (WISC-R) and the Kaufman Test of Educational Achievement (K-TEA). Higher levels of blood lead at age 24 months, but not at other ages, were significantly associated with lower global scores on both the WISC-R and the K-TEA after adjustment for potential confounders. Over the range of approximately 0 to 25 micrograms/dL, a 0.48-mumol/L (10 micrograms/dL) increase in blood lead at 24 months was associated with a 5.8-point decline in WISC-R Full-Scale IQ (95% confidence interval: 1.7 to 9.9, P = .007) and an 8.9-point decline in K-TEA Battery Composite score (95% confidence interval: 4.2 to 13.6, P = .0003). Mean blood lead level at age 24 months was 0.31 mumol/L (6.5 micrograms/dL; SD: 4.9, 90% percentile: 12.5). Slightly elevated blood lead levels around the age of 24 months are associated with intellectual and academic performance deficits at age 10 years.