Scientists have discovered a link between DDT and Alzheimer's disease.
In a small but intriguing study, researchers found that, on average, people with Alzheimer's disease had more of the DDT metabolite DDE in their blood serum than a control group in a similar age range.
"DDE can last in the body for a number of years," said lead author Jason Richardson of Rutgers-Robert Wood Johnson Medical School. "When you are looking at DDE levels, it is basically a snapshot of a person's lifetime exposure to DDT as well as DDE in the environment."
The findings were published in the journal JAMA Neurology.
Richardson said that while he expected to see a correlation between Alzheimer's and DDE levels, he did not expect it to be so dramatic. The average amount of DDE in the serum of the 86 people in the Alzheimer's group was four times greater than the average amount in the control group of 79.
"We can't say that DDT exposure is responsible for Alzheimer's with a study like this, but what we can say right now is that if you have higher levels of DDE you are more likely to be diagnosed with Alzheimer's," said Richardson.
DDT was used as a pesticide in the United States from the 1940s until it was banned in 1972 because of its effect on wildlife and human health. Farmers worldwide have been discouraged from using DDT to protect crops, but it is still used to control diseases such as malaria.
"Over 80% of us have measurable levels of DDE in our blood, that is a reality," Richardson told The Times. "We get it from legacy contamination or food that comes from countries using DDT."
None of the people in the study had DDE levels that were way beyond what is found in the general population. "The levels we observed were not outside what you find in the top 5% of people in the United States," he said.
He added that some of the participants who had high DDE levels did not have Alzheimer's.
"We need to do a lot more work to understand this association," he said. "It may not be as simple as different levels of exposure."
In an editorial about the study in JAMA Neurology, Steven DeKosky and Sam Gandy, who study Alzheimer's, said that while this study should be noted, its results are far from conclusive.
"For now, these conclusions should be considered as preliminary until there is independent confirmation in other populations," they write.
Richardson is working on it. "We have submitted grants to follow this up in much larger groups of people," he said. "That is the most important step -- to replicate this and to have it in a much larger sample."
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