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

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).