Association of cumulative lead and neurocognitive function in an occupational cohort.

Lead is a neurotoxicant that accumulates in bone with a half life of 25-30 years. To evaluate the association of lead biomarkers and cognitive function, a cohort of exposed and nonexposed workers who had been previously assessed in 1982 was retested approximately 22 years later. For the current assessment, both blood lead and tibia bone lead levels were determined. In addition, cognitive function was tested with the Pittsburgh Occupational Exposures Test battery, which had previously been administered in 1982. In exposed workers, bone lead level predicted lower current cognitive performance and cognitive decline over 22 years. In those lead-exposed workers older than age 55, higher levels of bone lead predicted poorer cognitive scores, suggesting vulnerability for older workers with higher past lead exposure. Finally, there was no association with bone lead level and recency of exposure, suggesting that cumulative body burden is most likely responsible for the progressive cognitive decrement evidenced with vulnerability because of aging.