Scientists at Rutgers University found that having higher levels of the breakdown product of the insecticide DDT (DDE) in your blood seems to fuel the disease and make you more likely to be diagnosed with Alzheimer’s. This research by no means uncovered a definitive cause of Alzheimer’s, but it’s a groundbreaking study that could inspire more research into the possible environmental factors—specifically chemical pesticides—that trigger Alzheimer’s, a brain disease that currently affects about 5 million people in the United States. If the findings pan out through further research, it could mean that testing for DDE levels in the body could lead to earlier diagnosis and treatment. “These results demonstrate that more attention should be focused on potential environmental contributors and their interaction with genetic susceptibility,” says Jason R. Richardson, PhD, associate professor in the department of environmental and occupational medicine at Robert Wood Johnson Medical School and a member of the Environmental and Occupational Health Sciences Institute (EOHSI). In the Rutgers study, conducted in coordination with Emory University Alzheimer’s Disease Research Center and the University of Texas Southwestern Medical School’s Alzheimer’s Disease Center, 74 out of the 86 Alzheimer’s patients involved had DDE blood levels almost four times higher than those of the 79 people in the control group who did not have Alzheimer’s disease. Patients with a version of ApoE gene (ApoE4), which greatly increases the risk of developing Alzheimer’s, along with high blood levels of DDE exhibited even more severe cognitive impairment than the patients without the risk gene. DDT has been banned in the U.S. since 1972, although other countries still use it. In the U.S., it was initially proclaimed to be safe and was sprayed on crops and inside of barns to deter pests. That “safe” chemical went on to cause massive environmental and wildlife damage. Should we be surprised that it’s probably attacking our brains, too? Not really. Because of its chemical structure, the substance remains inside of us for a long time—Dr. Richardson says the time it takes to excrete half of a given amount of DDT/DDE can be more than 10 years. “DDT was designed as an insecticide to kill insects,” he explains. “Unfortunately, insects and humans share the target of DDT: the voltage-gated sodium channel.” In other words, it attacks our brains, too. Younger people still have measurable amounts of DDE in their blood, but not at levels as high as scientists see in older adults. Mexican Americans have much higher levels, which could be because Mexico permitted the use of DDT until the 1990s, Dr. Richardson says. There’s no tried-and-true method for getting DDT out of the human body, either. But that point may be moot—the damage could occur early on. Scientists aren’t sure if its presence, built up over time, puts us at a greater risk of disease later in life, or if it threatens future health soon after exposure. What they do know is this: About 14% of the population carries the APOE4 gene variant, a genetic factor that increases a person’s risk of developing Alzheimer’s. Add pesticides to the mix, and you may have an even greater risk. “I think the take-home message is that chemical exposure is only one potential contributor to a complex disease like Alzheimer’s,” says Dr. Richardson. “Similarly, genes that have received the most attention and study are also only one component. I believe our study clearly suggests that researchers should broaden their thinking about contributors to complex disease and put more focus on gene-environment interactions.”
