The pesticide DDT, which is banned in the U.S. because of its toxic effects on wildlife and its potential to harm human health, may increase the risk for Alzheimer’s disease, according to the first study linking the chemical to the brain-ravaging illness.
People with Alzheimer’s disease had about four times the level of a DDT byproduct in their blood compared with those who didn’t have the form of dementia, according to research findings published Monday in the journal JAMA Neurology.
DDT, which was outlawed in the U.S. in 1972, is still found in blood samples because it can take decades for the chemicals to break down.
The pesticide is used in other countries, and U.S. residents can ingest it by eating fruits, vegetables and grains that are grown in those places, researchers said.
The study points to the need for more analysis about how environmental factors may interact with genes to boost Alzheimer’s risk, said Jason Richardson, the report’s lead author.
“We really need more attention on the role of environment and the interaction of your genes and environment for complex diseases such as Alzheimer’s,” said Richardson, an associate professor at the Robert Wood Johnson Medical School at Rutgers University in Piscataway, N.J. “The prevailing thought has always been it’s a genetic disease. Unfortunately that hasn’t panned out.”
Just how DDT and its byproduct, DDE, are linked to Alzheimer’s disease remains unclear. The pesticide may affect levels of proteins in the brain that are associated with the plaque that leads to the disease, Richardson said.
“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,” Richardson said.
More than 5 million people in the U.S. have Alzheimer’s, a number projected to triple by 2050, according to the Alzheimer’s Association.
Steven DeKosky, a professor of neurology at the University of Virginia, said the study provides a “wake-up call” to look at environmental factors for Alzheimer’s disease.
“We have spent so much time looking for the genetic underpinnings of the disease,” he said. “Now it’s time to start looking harder at the environment.”