A comprehensive study presented at the Alzheimer’s Association International Conference® 2025 in Toronto has established a connection between historical lead exposure and memory problems in older adults. The research indicates that individuals aged 65 and older who lived in areas with high atmospheric lead levels from 1960 to 1974 are approximately 20% more likely to experience cognitive issues today.
The analysis, which examined data from over 600,000 adults, reveals that nearly half of the U.S. population, equating to more than 170 million people, were exposed to high lead levels during their formative years. According to Maria C. Carrillo, Ph.D., chief science officer at the Alzheimer’s Association, this study provides critical insights into how lead toxicity continues to impact brain health in older adults.
Impact of Historical Lead Exposure on Cognition
The research is groundbreaking as it delves into how airborne lead from the past may have long-lasting effects on cognitive health. The study found that older adults who grew up in regions with moderate to extremely high historical atmospheric lead levels (HALL) reported memory problems at a significantly higher rate. Specifically, the data indicated that between 17% and 22% of individuals in these areas faced memory issues.
The researchers calculated the average atmospheric lead levels for different regions and correlated these with self-reported memory problems from the American Community Survey conducted between 2012 and 2021. Although they did not examine the specific sources of lead, they noted a direct correlation between higher traffic densities in urban areas and elevated atmospheric lead levels.
Dr. Eric Brown, the lead author of the study and associate scientist at the Centre for Addiction and Mental Health, emphasized the research’s potential to enhance our understanding of the pathways that may lead to dementia and Alzheimer’s disease.
Lead was initially added to gasoline to improve vehicle performance, but its hazardous effects on health and the environment led to a gradual phase-out starting in 1975. Dr. Esme Fuller-Thomson, senior author of the study, highlighted that children in the mid-1970s had blood lead levels that were 15 times higher than those of today’s children, with an alarming 88% of them exceeding what is now considered dangerously high.
Continued Risks from Environmental Lead Exposure
While the risks associated with atmospheric lead have diminished, other sources, such as old lead paint and water pipes, continue to pose threats. Dr. Brown advises individuals previously exposed to atmospheric lead to mitigate other risk factors for dementia, including managing blood pressure, avoiding smoking, and maintaining social connections.
Another study presented at the conference revealed that older adults living within approximately 5 km of a lead-releasing facility, such as those involved in glass or electronics manufacturing, exhibited greater memory and cognitive difficulties compared to those residing farther away. This research, which encompassed a diverse group of 2,379 participants, reinforces the ongoing concerns about the cognitive impacts of environmental lead exposure, particularly in communities that already face health disparities.
Dr. Kathryn Conlon, senior author of the study and associate professor at the University of California, Davis, noted that lead exposure in adulthood could significantly impair cognitive performance within a few years. The study highlighted that in 2023, there were 7,507 lead-releasing facilities in the U.S., emphasizing the need for continued vigilance in managing environmental lead exposure.
Moreover, a third study indicated that even low levels of lead exposure could lead to permanent changes in brain cells, increasing the risk of developing Alzheimer’s disease. Researchers exposed human brain cells to varying lead concentrations, finding that those exposed to levels as low as 15 parts per billion exhibited signs of early dysfunction and damage.
Dr. Junkai Xie, the lead author, explained that these findings illuminate how lead exposure, particularly during early life, may leave enduring effects on the brain, making it more susceptible to age-related diseases.
These studies underscore the long-term consequences of lead exposure on cognitive health, highlighting an urgent need for continued research and public health initiatives to address this critical issue.
