Adults exposed to high levels of air pollution are at an increased risk of developing Alzheimer’s disease. That’s the finding of a new Emory University study that is considered the largest of its kind.

Published in “Environmental Health Perspectives,” the study gathered data from 1,113 participants in the Atlanta metropolitan area. Analysis of that data revealed positive biomarkers for Alzheimer’s disease among participants exposed to ambient and traffic-related air pollution at their homes. According to Emory University, the study backs up the results of previous smaller efforts that have suggested air pollution contributes to degeneration in the brain.

“Together, our recent studies represent both ends of the spectrum,” explained Anke Huels, PhD, lead author and an assistant professor in the Department of Epidemiology at Emory’s Rollins School of Public Health, in a press release.

“In our previous study we showed associations between residential exposure to air pollution and Alzheimer’s-related changes in the brain in an autopsy cohort and now, we found similar results in a study of living adults who were on average 15 years younger and cognitively healthy. This is important because it shows that residential air pollution can negatively affect our brain even decades before we actually develop Alzheimer’s disease. This points to a sensitive time period for both exposure and opportunity, because that is time when prevention strategies and interventions are most effective.”

According to the Atlanta-based Centers for Disease Control and Prevention (CDC), as many as 5.8 million Americans lived with Alzheimer’s disease in 2020. As the U.S. population ages, those numbers will grow. By 2060, the CDC project the number of cases within the U.S. to nearly triple to 14 million people.

“We know that air pollution is generally bad for human health, including brain health,” James Lah, MD, PhD, principal investigator of the Emory Healthy Brain Study and an associate professor in the Department of Neurology at Emory’s School of Medicine, said in the press release.

“By showing a relationship to levels of the amyloid protein in the cerebrospinal fluid, this study suggests that air pollution might increase the risk of developing Alzheimer’s disease. The flip side of that is that by cleaning up our environment, we might also help reduce the burden of Alzheimer’s disease.”