A-20IQ and Memory Functioning among Children with a History of Elevated Blood Lead Levels

Objective: To examine the relationship between peak blood lead levels (BLLs), IQ and memory performance among a group of children evaluated in a forensic context. Method: Scores from the Wechsler Intelligence Scale for Children—3rd edition (WISC-III) and the Children's Memory Scale (CMS) were examined among 68 children with a mean age of 9.3 years (SD = 2.6) and average peak BLLs of 42.5 µg/dL (SD = 23.4). Results: Peak BLLs were not significantly correlated with either full-scale IQ (FSIQ) (r = .118, ns) or the CMS General Memory Index (GMI; r = −.056, ns). Two regression analyses were completed regressing peak BLLs on FSIQ and the CMS GMI, while controlling for age, gender, and education. The overall model accounted for approximately 16% of the variance in FSIQ scores (R² = .16, F(4, 62) = 3.0, p < .05). However, the proportion of variance in FSIQ scores explained uniquely by peak BLLs was approximately 0.8% (semi-partial correlation = .092, t(66)= .79, ns). The overall model accounted for approximately 22% of the variance in CMS GMI (R² = .22, F(4, 27) = 1.95, ns). The proportion of variance in CMS GMI explained uniquely by peak BLLs was 2% (semi-partial correlation = −.143, t(31)= −.846, ns). Because peak BLLs were not normally distributed, a logistic transformation was performed on all analyses; however, this did not influence any of the results. Conclusions: Peak BLLs accounted for no more than 2% of the variance in both IQ and memory scores among children with a history of elevated BLLs. These findings are consistent with those reported by the Center for Disease Control (2005).