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Alzheimer's Disease Health Center

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
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WebMD News from HealthDay

By Dennis Thompson

HealthDay Reporter

MONDAY, Jan. 27, 2014 (HealthDay News) -- Exposure to the banned pesticide DDT appears to increase a person's risk of Alzheimer's disease, a new study reveals.

Blood drawn from a small sample of Alzheimer's patients contained nearly four times greater levels of a DDT byproduct than blood taken from a group of healthy people, researchers found.

Exposure to DDT appears to promote the development of amyloid beta plaques, which clog the neurons of Alzheimer's patients and are suspected to be a cause of the disease, said study author Jason Richardson, an assistant professor of environmental and occupational medicine at Rutgers-Robert Wood Johnson Medical School in New Jersey.

The pesticide also might further increase Alzheimer's risk for people who already have a genetic predisposition toward developing the degenerative disease, Richardson said.

People scored significantly lower on logic and reasoning tests if they had high levels of the DDT byproduct and an Alzheimer's-prone version of the apolipoprotein E (ApoE) gene, compared with people who had similarly high levels of DDT but no genetic risk.

However, Richardson added that it's too soon to tell if the pesticide and the faulty gene have some sort of interaction or simply pose their own individual risk for Alzheimer's.

"They may just act separately, or they may converge. We don't know yet," he said of the two risk factors. "If both were on board, you did worse than if you had only one of them."

U.S. officials banned DDT in 1972 due to concerns over the pesticide's effect on wildlife, especially birds. Since the 1940s, it had been used extensively in agriculture and for mosquito control.

A worldwide ban on DDT use in agriculture has been in effect since 2004, but it has lingered in the environment and it is still in limited use in foreign countries where mosquitos carry malaria and other infectious diseases.

This research, published online Jan. 27 in JAMA Neurology, grew out of earlier research in which Richardson and colleagues linked the banned pesticide beta-hexachlorocyclohexane (beta-HCH) to Parkinson's disease.

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