DDT Exposure Tied to Increased Risk and Severity of Alzheimer's Disease

Exposure to the banned pesticide DDT may heighten the risk and severity of Alzheimer's disease, a latest U.S. study claims. This association is more prominent in older adults.

The pesticide DDT (dichlorodiphenyltrichloroethane) is well known for its harmful effects on the environment. Studies have also tied the use of this insecticide to various health hazards due to which environmentalists have campaigned for an international ban of this product. Though its use in the United States was banned in 1972, certain countries continue to use it as a pesticide.

But in a new finding, researchers at the Rutgers University claim that People diagnosed with Alzheimer had higher levels of the synthetic pesticide DDE (Dichlorodiphenyldichloroethylene), a byproduct of DDT, in their blood.  This was four times higher than the levels seen in a healthy person with no Alzheimer.

"I think these results demonstrate that more attention should be focused on potential environmental contributors and their interaction with genetic susceptibility," says Jason R. Richardson, associate professor in the Department of Environmental and Occupational Medicine at Robert Wood Johnson Medical School.  "Our data may help identify those that are at risk for Alzheimer's disease and could potentially lead to earlier diagnosis and an improved outcome."

In the United States, this synthetic pesticide was introduced during World War II to control the damage caused by insects in crops. Though over the last three decades the levels of these pesticide have dropped significantly in the U.S., it is still present in 75-80 percent blood samples collected from the  Centers for Disease Control and Prevention for a national health and nutrition survey. 

Scientists say that since the chemical takes almost a decade to breakdown into the environment, traces of it are still present in the blood samples. People expose themselves to this chemical by consuming imported fruits, grains and vegetables where DDT is still being used. Eating fish taken from contaminated waterways also plays a key role in exposing humans to the chemicals.

 This is the first study that links a particular chemical to a neurodegenerative disease like Alzheimer's. In this study, the Rutgers researchers in collaboration with researchers at Emory University and University of Texas Southwestern Medical Center examined the blood samples of over 86 people who were diagnosed with Alzheimer's. The average age was 74. The researchers noticed that 74 of the 86 patients had traces of DDE in the blood samples that were four times higher than in the 79 members of the control group( a group of healthy individuals).

People who carried the gene ApoE , linked with the risk of developing Alzheimer's, and high blood levels of DDE, suffered from severe cognitive impairment compared to patients with the ApoE gene alone.

"This study demonstrates that there are additional contributors to Alzheimer's disease that must be examined and that may help identify those at risk of developing Alzheimer's," says Richardson. "It is important because when it comes to diagnosing and treating this and other neurodegenerative diseases, the earlier someone is diagnosed, the more options there may be available."

The study was published in JAMA Neurology.