An examination of the relation between early childhood lead (Pb) exposure and cognitive intraindividual variability in a medicolegal sample.

Abstract

Objective: Lead (Pb) exposure, particularly during early childhood, is a major health concern associated with diminished cognitive performance. Most prior research has focused on Full-Scale IQ (FSIQ). This study examined relations between childhood blood Pb exposure and cognitive intraindividual variability (IIV) in a medicolegal sample.

Method: Two-hundred sixteen adolescent participants (50% female; 82.4% Black; age M = 20.47, SD = 2.05 years; education M = 10.94, SD = 1.56 years) completed a neuropsychological battery more than a decade after documented Pb exposure. All participants passed the Test of Memory Malingering or Word Memory Test. IIV was operationalized as an examinee's performance dispersion across a battery of nine test scores (IIV dispersion). Continuous Performance Test-Second Edition Variability also served as an index of IIV inconsistency (within-task reaction time variability). Associations among blood Pb exposure, IIV metrics, and FSIQ were examined using bivariate correlations, group comparisons, and multiple regression.

Results: IIV dispersion was positively correlated with childhood average blood Pb (r = .17-.22) and the average of the highest three Pb values (r = .20-.25) and negatively correlated with FSIQ (r = -.32 to -.55). FSIQ was unrelated to Pb outcomes. Demographic and psychiatric factors were unrelated to Pb and IIV variables. Within-group analyses revealed a dose-response pattern, with the high Pb group showing greater IIV-dispersion metrics than the low and medium exposure groups (d = |0.38| to |0.50|). Regression analyses indicated that IIV-dispersion metrics predicted Pb exposure above-and-beyond FSIQ and IIV inconsistency.

Conclusions: These results support that cognitive IIV, particularly dispersion-based indices, is a sensitive marker of Pb-related neurocognitive dysfunction, providing incremental information beyond FSIQ and IIV inconsistency. (PsycInfo Database Record (c) 2026 APA, all rights reserved).