Air pollution linked to accelerated Alzheimer’s disease

Exposure to air pollution is connected with worsening Alzheimer’s disease, including faster and more aggressive cognitive impairment, according to a new study published in JAMA Neurology this September.

Researchers at the University of Pennsylvania autopsied more than 600 brains from dementia patients and mapped the results against geographic air pollution data. They found that the brains of people with Alzheimer’s who lived in areas with worse air quality were 19% more likely to show severe changes, including protein buildups that are hallmarks of the disease’s progression.

The study also found that living amid more air pollution is associated with mental decline, including memory loss and impaired judgment, based on cognitive tests administered several years before the patients’ deaths. “The more air pollution you’re exposed to, the faster your cognitive decline over time,” said Dr. Edward Lee, one of the study’s lead authors and the co-director of the Penn Institute on Aging.

Lee and his colleagues found that most of this impairment was directly tied to changes in the brain from the disease, rather than other factors related to air pollution, such as difficulty breathing that could starve the brain of oxygen. 

“This is one of the keynote studies looking at this area of research,” said Dr. Thomas Wisniewski, director of NYU Langone’s Alzheimer’s Disease Research Center and Center for Cognitive Neurology, who was not involved in the study. He noted that it “makes a very strong case” for a connection between air pollution and Alzheimer’s by directly examining changes to the brain itself, rather than indirect markers of the disease — the “gold standard” method in Alzheimer’s research. 

Approximately 7.2 million Americans are living with Alzheimer’s dementia in 2025, according to the Alzheimer’s Association. It is the most common form of dementia.

“Other studies show us there are more cases of Alzheimer’s or dementia in higher exposure areas, but this study shows us these cases are also more severe,” said Dr. Katrin Burkart, who studies environmental effects on health at the University of Washington and was not involved in the study. “It gives us a glimpse into what could be the neuropathology behind the impact of air pollution.”

The study focused on air pollution made of microscopic particles less than 2.5 micrometers wide — about 30 times smaller than the width of a human hair — that when inhaled can enter the bloodstream and cause an array of health problems. This pollution comes from a variety of sources, including wildfire smoke, car exhaust and construction debris, according to the U.S. Environmental Protection Agency.

Despite ongoing progress reducing air pollution, experts noted that levels are still too high for human health. “The elephant in the room is really that air pollution is a huge health hazard,” Burkart said. “There is more progress to be made and there is a lot to be gained from continuing to reduce air pollution levels.”

Still, Lee cautioned against making drastic personal changes like moving to an area with better air quality, urging a focus on broader measures instead. “We should advocate on a public policy standpoint for improved air quality,” he said.

“This is a societal issue,” Wisniewski said. “Dementia is expected to double in the coming decades in the United States and much of the world, so curbing pollution might lower the expected dementia rates in this aging population.”

“The cleaner the better, is what the whole field is finding,” Lee said.