Prenatal and Early Postnatal Lead Exposure and Later Adulthood Cognitive Function in the St. Louis Baby Tooth-Later...

Early exposure to lead has known neurocognitive impacts in childhood, but few studies have examined the long-term impacts extending into later adulthood. We estimated associations between prenatal and early postnatal lead exposure and later adulthood cognitive function and examined specific periods of exposure and effect modification by sex.

The St. Louis Baby Tooth-Later Life Health study (SLBT) is a prospective cohort study that re-enrolled participants of the Baby Tooth Survey, originally centered in St. Louis, MO, who had donated their deciduous teeth between 1958 and 1972. SLBT participants completed surveys and a battery of cognitive tests in later adulthood. Tooth dentin lead concentrations were assessed using laser ablation inductively coupled plasma mass spectrometry across prenatal (second and third trimesters) and early postnatal periods. Cognitive function was assessed using a computerized cognitive battery taken at home using computers or personal digital devices. We used weighted generalized estimating equations to estimate associations between lead exposure and a composite outcome of later adulthood cognitive function.

A total of 715 participants (52% female, mean age at cognitive testing: 62 years) had completed tooth metals analysis. The association between lead and performance on the vocabulary test was positive and statistically significantly different from the other tests. For each part per million (ppm) higher second trimester tooth dentin lead concentration, performance on a composite of tests excluding vocabulary was 0.07 SDs lower (95% CI -0.15 to 0.02). This effect was similar when coadjusting for third trimester and postnatal lead. These findings were driven by females, among whom each 1 ppm higher second trimester lead concentration was statistically significantly associated with 0.16 SD worse cognitive function (95% CI -0.29 to -0.03), equivalent to a 3-year difference in age in the same model. The results were robust to adjustment for additional potential sources of confounding and alternate methods of averaging tooth lead concentrations.

We found suggestive evidence for associations between early lead exposures and later adulthood cognitive function, although these only reached statistical significance for second trimester lead exposure among females. A coadjusted analysis suggested the second trimester may be most relevant for later cognitive function.