As rates of dementia continue to climb across the United States, new research from the University of Michigan School of Public Health suggests that long-term exposure to lead may play a significant role in the development of cognitive decline. The study indicates that older adults who have accumulated higher levels of lead in their bodies over the course of their lives face a substantially greater likelihood of developing Alzheimer’s disease and other forms of dementia. While lead exposure has long been recognised as harmful to the brain, the findings highlight how its effects may continue to influence neurological health decades after initial exposure.
According to the researchers, the scale of the potential impact is considerable. Kelly Bakulski, an associate professor of epidemiology at the University of Michigan School of Public Health and one of the study’s senior authors, explained that the analysis provides the first empirical evidence suggesting that roughly 18 per cent of new dementia cases in the United States each year may be connected to cumulative lead exposure. With around half a million Americans diagnosed with dementia annually, this estimate suggests that close to 90,000 cases could potentially be linked to the long-term effects of lead stored in the body.
The study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, found striking differences in risk between individuals with varying levels of lifetime exposure. Participants whose bone lead concentrations ranked in the highest quarter faced nearly three times the risk of developing Alzheimer’s disease compared with those in the lowest quarter. They were also more than twice as likely to develop dementia from any cause. These results point to cumulative lead exposure as a major environmental factor that may contribute to neurodegenerative disease, yet one that has historically received less attention in dementia research.
To explore this relationship, the research team analysed data from participants in the National Health and Nutrition Examination Survey (NHANES), linking these records with Medicare claims and mortality data spanning up to three decades of follow-up. The investigators used machine learning techniques to estimate the amount of lead stored in bone tissue, which acts as a biological archive of lifetime exposure. Unlike measurements that capture only recent contact with lead, bone lead levels reflect the accumulation of the metal over many years.
One of the most important findings of the study was that bone lead levels showed a strong association with dementia risk, while current blood lead levels did not. Sung Kyun Park, a professor of epidemiology and environmental health sciences and a senior author of the research, noted that this distinction is crucial for understanding the long-term consequences of exposure. Lead circulating in the blood typically reflects exposure from the past few weeks, whereas lead embedded in bones can remain for decades. As a result, bone lead provides a much clearer picture of the lifetime burden that may contribute to chronic diseases such as dementia.
Many of the adults included in the study were born before 1980, when environmental lead exposure was significantly higher due to the widespread use of leaded petrol and lead-based paint. Researchers explain that once lead enters the body, it can become stored in bone tissue and remain there for many years. As people age, some of this stored lead may gradually be released back into the bloodstream and potentially reach organs such as the brain. The researchers emphasise that reducing remaining sources of lead exposure—including ageing paint, old plumbing systems, contaminated soil, and industrial pollution—remains essential for protecting both current and future generations from accumulating levels that may increase the risk of dementia later in life.
More information: Xin Wang et al, Exposure to lead and incidence of Alzheimer’s disease and all-cause dementia in the United States, Alzheimer’s & Dementia. DOI: 10.1002/alz.71075
Journal information: Alzheimer’s & Dementia Provided by University of Michigan School of Public Health
