Early childhood blood lead concentrations and selective attention among school-age children: Evidence consistent with a causal association and effect modification by sleep duration

Selective attention is essential for cognitive and behavioral self-regulation. However, the association between lead exposure and selective attention remains unclear. We examined the association between blood lead levels and selective attention, and evaluated whether this association is influenced by sleep duration. We used data from a prospective cohort of 377 Korean children. Blood lead concentrations and Stroop Color and Word Test (SCWT) scores were repeatedly measured at 6, 8, and 10 years of age. Generalized propensity scores (GPSs) were generated using linear regression models predicting lead levels. Associations between lead levels and SCWT scores were assessed using causal inference approaches, such as linear mixed models adjusted for both GPS and potential confounders, as well as doubly robust estimation models. In models adjusted for both GPS and potential confounders, a doubling of lead levels was associated with lower color [β = -1.46, 95 % confidence interval (CI): -2.63, -0.30] and color-word (β = -1.52, 95 % CI: -3.00, -0.04) test scores. In doubly robust models, these associations persisted for the color (β = -1.35, 95 % CI: -2.36, -0.34) and color-word (β = -1.33, 95 % CI: -2.61, -0.04) test scores. The associations varied by sleep duration, with stronger effects observed among children sleeping ≤ 8 h compared with those sleeping longer. By applying multiple causal inference approaches, this study provides robust evidence that lead exposure impairs selective attention in school-age children. The detrimental associations were amplified among those sleeping ≤ 8 h, suggesting that sufficient sleep may mitigate the neurotoxic effects of lead exposure.