DDT Exposure May Raise Alzheimer's Risk: Study
Researchers say those with the disease had 4 times higher blood levels of byproduct of banned pesticide
That earlier study also contained a small sample of Alzheimer's patients, Richardson said. Those patients did not have elevated levels of beta-HCH but they did have higher levels of a byproduct of DDT called DDE. The researchers decided to go back and look into a possible link between DDT and Alzheimer's.
This new research is based on blood samples drawn from 86 Alzheimer's patients between 2002 and 2008.
Even though DDT has been banned for decades, it still turns up in human blood samples due to its long half-life, the authors noted. DDE can remain in a person's body for up to a decade, and despite the ban people still are exposed to DDT through imported food or contamination that remains in United States soil and waterways.
Researchers found that people with Alzheimer's disease had 3.8 times the level of DDE in their blood when compared to healthy people.
The investigators further found that people with DDE levels in the top third of the sample had four times the risk of developing Alzheimer's.
The team did some follow-up lab research involving human brain cell cultures to investigate possible explanations for the link. They found that when they exposed the cells to DDE for 48 hours, levels of a protein linked to beta amyloid plaques increased by nearly 50 percent.
"Levels of DDE that correspond to that of people who are highly exposed increases the levels of a protein associated with the plaques that build up in the brains of people with Alzheimer's," Richardson said.
People who want to limit their exposure to DDT should avoid eating fish caught in contaminated waterways and be careful eating food grown or raised in countries where the pesticide is still used to control mosquitos.
While the results are interesting, the study's small sample makes it difficult to draw any firm conclusions about the link between DDT exposure and Alzheimer's disease risk, said Heather Snyder, director of medical and scientific operations for the Alzheimer's Association.
"This requires further study, but it does give us valuable information that will help better ask future research questions," Snyder said. "It gives us some good reasons that we as a field should explore elements in the environment that could influence Alzheimer's risk."