There is a link between exposure to the pesticide DDT and Alzheimer’s disease, according to a new study published in JAMA Neurology. Eighty percent of Alzheimer’s patients involved in the study had evidence of exposure to DDT. DDT was a widely used pesticide in the U.S. for over 30 years before it was banned by the Environmental Protection Agency in 1972.

“In our study, we found that of the patients that we sampled had on average about four times the level of DDE [a compound created when DDT breaks down] in their blood, and this was associated with about a fourfold increase in risk for being diagnosed with Alzheimer’s,” says Dr. Jason Richardson, the lead author of the new study. “We have to be very cautious with this. Studies like this can’t really tell you about the cause of the Alzheimer’s.”

To hear more of Lizzie O’Leary’s interview with Dr. Jason Richardson, click the audio player above.