Low level lead exposure in early childhood and parental education on adolescent IQ and working memory: A cohort study

BACKGROUND: The independent effect of lead exposure and parental education on children’s neurocognition is well-documented. However, few studies have examined the combined effect of childhood lead exposure and parental education on adolescent neurocognition, especially in China. OBJECTIVE: Examine both the combined and interactive effect of childhood blood lead levels (BLLs) and parental education on early adolescent neurocognition. METHODS: 417 children from a longitudinal cohort study in Jintan, China had BLLs measured at 3–5 years and 12 years, parental education levels assessed at 3–5 years, and neurocognitive outcomes tested at 12 years. RESULTS: BLLs at 3–5 years were inversely associated with adolescent IQ (β −0.55 95% CI: −0.97, −0.13) but not working memory (β −0.06 95% CI: −0.23, 0.11) and parental education was positively associated with adolescent IQ (β 0.68 95% CI: 0.19, 1.17) and working memory (β 0.24 95% CI: 0.04m 0.44). BLLs and parental education evidenced combined effects on neurocognition, where children with higher BLLs and lower fathers’ education had mean IQ scores 7.84 (95% CI: −13.15, −2.53) points lower than children with lower BLLs and higher fathers’ education. There were significant associations between parental education and working memory, however, not with BLLs. The interaction between mother and father high school education and BLLs was insignificant for effects on IQ and working memory. SIGNIFICANCE: Childhood lead exposure and parental education levels have a combined and long-term impact on IQ, evidence that may partially explain disparities in lead exposure associated outcomes and highlight those children at greatest risk for neurocognitive deficits. IMPACT STATEMENT: Children continue to be exposed to low-levels of environmental lead in China and globally, warranting examination of the impact of such exposures. This paper demonstrates that even relatively low-level lead exposure in early childhood significantly influences adolescent neurocognitive functioning. Furthermore, co-existing social determinant of health-related variables, measured here as parental education, have a combined impact on neurocognition. These results highlight children at greater risk for neurocognitive deficits and demonstrate the need to examine the influence of lead exposure within the broader socio-ecological environment, as these factors work in tandem to influence longer-term neurocognitive outcomes.