Long-Term Lead Exposure May Increase Risk of Alzheimer’s Disease, Dementia Diagnosis: Study

Researchers determined that reducing lead exposure could prevent nearly 1 million cases of dementia in future generations.

New research suggests that long-term lead exposure is linked to a higher risk of dementia and nearly triple the risk of developing Alzheimer’s disease.

Lead exposure was widespread in the United States for decades before the 1990s, when lead based paint, leaded gasoline, contaminated drinking water systems and certain industrial emissions were far more common. As a result, millions of Americans were routinely exposed to elevated lead levels during childhood and early adulthood, often without knowing it.

Now, findings published on February 12 in the journal Alzheimer’s & Dementia indicate that individuals who grew up during that period of widespread lead exposure face a significantly higher risk of cognitive decline, including an increased likelihood of developing Alzheimer’s disease later in life.

Lead Exposure Risks

A wide body of research has linked lead exposure to numerous health problems, including learning disabilities and developmental delays, with even low level exposure during pregnancy and early childhood known to potentially cause lasting harm to children’s cognitive development.

The American Academy of Pediatrics (AAP) indicates there is no safe lead exposure level for children, warning that any level of exposure can increase the risk of injuries to the brain and nervous system. Supporting research published earlier this year also found that childhood lead exposure is associated with a higher risk of depression during adolescence.

For the new study, researchers from the School of Public Health at the University of Michigan examined blood lead levels in more than 8,000 people using data from the National Health and Nutrition Examination Surveys from 1988 to 1994 and 1999 to 2016.

Led by Dr. Xin Wang, the team then looked at the lead levels in bones, including the patella and tibia.

Researchers linked the data to Medicare claims and death records spanning up to 30 years. They then used machine learning algorithms to estimate bone lead concentrations, a marker of cumulative lifetime exposure. Unlike blood lead levels, which reflect exposure over roughly the previous 30 days, bone measurements provide a clearer picture of long term lead accumulation in the body.

People who had high bone levels of lead faced nearly twice the risk of developing all-cause dementia. Participants with the highest levels of lead in their bones faced three times the risk of Alzheimer’s disease.

The data also showed that patients with patella bone lead levels in the lowest 25th percentile experienced an 18 percent reduction in dementia risk compared to those with higher concentrations.

Overall, the findings suggest that cumulative lead exposure over a lifetime is a significant risk factor for Alzheimer’s disease. In contrast, current blood lead levels were not useful in assessing long term risk, since they reflect only recent exposure.

Instead, researchers found that bone lead measurements provide a more reliable indicator of exposure accumulated over years and decades. The team noted that lead stored in bone can later be released back into the bloodstream and migrate to vital organs, including the brain, potentially contributing to neurodegenerative damage.

“This finding suggests that circulating lead, as reflected by blood lead, may not be a relevant indicator of long-term cumulative exposure or suitable for assessing risk for chronic diseases such as (Alzheimer’s disease) and all-cause dementia.”

— Dr. Xin Wang, Exposure to lead and incidence of Alzheimer’s disease and all-cause dementia in the United States

With more than half a million Americans diagnosed with dementia each year, researchers concluded that reducing lead exposure and monitoring bone lead levels could prevent more than 900,000 future cases.

Wang’s team warned that it is important to continue efforts to eliminate remaining lead sources in communities, including old paint, old pipes, contaminated soil and lead producing industrial facilities.

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