Scientists Say This Sneaky Factor Impacts Brain Health, Increases Alzheimer’s Risk

Research shows that certain lifestyle factors impact everything from heart disease risk factors to dementia. Aspects of your routine, like diet, exercise, and how much sleep you get, all may play a role. But now, scientists say one sneaky element may increase your heart disease and Alzheimer’s risks: air pollution.

Air pollution has been linked with a slew of serious health conditions, including heart disease and asthma. A new study of nearly 28 million older Americans adds to that.

For the study, which was published in PLOS Medicine, researchers analyzed data from more than 27.8 million Americans on Medicare, 65 or older, between 2000 and 2018. The researchers compared levels of air pollution exposure with new cases of Alzheimer’s disease, taking into account other chronic health conditions.

The researchers discovered that people who were exposed to higher levels of air pollution had a greater risk of developing Alzheimer’s disease and the risk grew with more air pollution exposure. (The link was stronger in people who had experienced a stroke in the past.)

“These findings highlight the need for air quality interventions as part of dementia prevention strategies in aging populations, especially those facing overlapping environmental and clinical vulnerabilities,” the researchers wrote in the conclusion.

Meet the experts: Davide Cappon, Ph.D., director of neuropsychology at Tufts Medical Center; Auriel A. Willette, Ph.D., an associate professor in the Department of Neurology at Rutgers Robert Wood Johnson Medical School; Clifford Segil, D.O., a neurologist at Providence Saint John’s Health Center in Santa Monica, CA.

What’s behind this link and, more importantly, how can you combat it? Here’s what experts suggest.

How might air pollution raise the risk of Alzheimer’s disease?

This isn’t the first study to link air pollution with Alzheimer’s disease. Research published in JAMA Neurology in 2025 analyzed brain samples from more than 600 autopsies and found that for every 1 microgram per cubic meter increase in PM2.5 (tiny particulate matter that can be absorbed into the bloodstream), the risk of having a higher build-up of Alzheimer’s disease markers (amyloid and tau) increased by 19%.

The latest study found that air pollution may contribute directly to Alzheimer’s disease risk (vs. causing conditions that may also raise the risk of the disease). Why? Scientists don’t know at the moment, but there are some theories.

“Tiny pollution particles don’t just affect the lungs,” explains Davide Cappon, Ph.D., director of neuropsychology at Tufts Medical Center. “When we breathe them in, they can get into the bloodstream and put stress on the body.”

With time, that stress may impact blood vessels and increase the risk of conditions like high blood pressure, stroke, and even depression, Cappon says. “What’s important in this research is that air pollution appears to raise the risk of Alzheimer’s disease even beyond those conditions,” he continues. “In other words, it’s not just that pollution causes high blood pressure or stroke, which then lead to Alzheimer’s—pollution itself seems to have a more direct impact on brain health.”

But air pollution may also increase inflammation in the body, along with oxidative stress that can impact brain tissue, says Auriel A. Willette, Ph.D., an associate professor in the Department of Neurology at Rutgers Robert Wood Johnson Medical School. (Oxidative stress is an imbalance of unstable molecules and the body’s ability to neutralize them.)

“Higher long-term exposure not only raises risk, but some of the biological precursors thought to lead to Alzheimer’s disease, including higher brain amyloid burden,” Willette says. “So air pollution could push the brain into a more vulnerable state by impacting inflammation, vascular, and amyloid-related pathways that may contribute to Alzheimer’s disease.”

The effect being a little stronger in people who already had a stroke “makes sense,” Cappon says. “When the brain’s blood vessels are already damaged, it may be less able to handle additional stress from environmental exposures,” he says. “In simple terms, a more vulnerable brain has less resilience.”

But Cappon stresses that air pollution is unlikely to be the only thing that causes Alzheimer’s disease. “Alzheimer’s disease doesn’t develop from one single cause,” he says. “It reflects a mix of factors that build up over decades—genetics, vascular health, metabolism, lifestyle, education…” Air pollution may simply be one piece of the puzzle, he says. “It’s not likely to be the dominant driver on its own, but it may add stress to the brain over time, especially in people who already have vascular or other health vulnerabilities,” Cappon adds.

Still, Willette underscores this: “The public-health message is clear: When exposure differences are that large and persist for years, air pollution is a serious environmental risk factor to consider.”

What can you do to combat it?

The researchers in the latest study note that improving air quality may be an important way to lower the risk of dementia. While you can’t do anything about the air quality outside, you can impact the air you breathe indoors, Cappon says. Consider these options if air pollution is common in your area:

• Use an air purifier. Not all air purifiers filter out PM2.5, making it important to look for one designed to do this. HEPA filters can typically pull these particles out of your air, though.
• Close your windows and doors. Keeping windows and doors closed helps to minimize the amount of air pollution inside your home.
• Wear a mask outside. An N95 mask can help to filter out PM2.5 on high-pollution days.
• Check the air quality before outdoor exercise. The air quality index (AQI) is a rating system that checks the severity of pollution in your area on a scale from zero to 500. An AQI of 50 or below is considered a good air quality day; an AQI over 300 is considered hazardous. Planning outdoor workouts around air quality can lower your exposure to PM2.5.

Willette notes this, though: “While these measures are sensible for reducing particulate exposure, we do not yet have studies that tie such reductions to reduced dementia risk.”

Other ways to lower your risk of Alzheimer’s disease

Doctors still don’t know exactly what causes Alzheimer’s disease, which makes prevention tricky. However, doctors say there are some key behaviors that seem to be linked to a lowered risk of Alzheimer’s disease:

• Exercise for 150-plus minutes a week. A healthy body is supportive of a healthy brain, says Clifford Segil, D.O., a neurologist at Providence Saint John’s Health Center in Santa Monica, CA. “Keep active,” he says.
• Engage your brain. Dr. Segil often recommends that his retired patients take classes at a local community college or other academic institutions to keep them learning new things. However, reading about subjects you’re unfamiliar with, listening to music, or doing puzzles may help, too, he says.
• Interact with friends. Socializing is helpful for brain health, according to Dr. Segil. It also helps to combat loneliness, which is linked to a 31% greater risk of developing dementia.