S06: Lead’s long-term legacy: what past exposures can tell us about future disease, Room 315, Floor 3, August 27, 2019, 10:30 AM - 12:00 PM
With the assistance of humans, lead has insinuated itself into human bodies for centuries, wreaking havoc on humans’ vascular systems, blood, kidneys, moods, and developing brains. As human lifespans have stretched into seven and eight decades, the question has arisen as to whether lead might affect the risk of conditions of older age, particularly dementia. Dementia is extraordinarily common with advancing age, affecting 1 in 10 adults ages 65 years and older and nearly a third of adults 85 and older. More than other conditions of older age, dementia is condition that many people would like to avoid developing. Lead is a suspect in the etiology of dementia owing to its potent neurotoxicity and cardiovascular toxicity, as well as its capacity to linger in the body for decades. Over the past few decades, lead exposures have plummeted to historically low levels, due largely to a near complete ban of leaded fuel and paint. Even so, historic exposures may yet reverberate into the future of the dementia epidemic: nearly 90% of U.S. children in 1976 had blood lead levels exceeding 10 microg/dL, and many people who were born as late as the 1990s may have incurred childhood exposures that could influence their dementia risks later in life.
High-quality studies that directly address this important public health question about lead’s effect on dementia risk are essentially absent. Studies with high-quality assessments of cumulative lead exposure rarely also entail high-quality assessments of dementia, and vice versa. Yet abundant indirect mechanistic and epidemiologic evidence supports a role of lead in dementia etiology. I will trace that line of evidence, which includes studies of well-characterized lead exposure and preclinical outcomes. I will also characterize the key challenges in conducting this research, including differential misclassification and selection bias, and how future research might overcome them.