Cleaner air, clearer mind: Air pollution linked to higher risk of Alzheimer’s disease

SAN FRANCISCO, Calif. — Location, location, location. Choose very wisely where you spend your days and call home, it may determine your cognitive health in old age. Researchers at the University of California, San Francisco report older Americans with cognitive impairment are more likely to show amyloid plaques in their brains (a major predictor of Alzheimer’s) if they live in areas with high levels of air pollution.

Scientists already know about various factors that can raise one’s risk of dementia, such as diabetes or smoking. Now, it appears air pollution from sources like cars, factories, forest fires, and power plants may need to go on that list as well.

How air pollution is linked to dementia, Alzheimer’s

Study authors analyzed the PET scans of over 18,000 elderly Americans with an average age of 75 years-old. Participants came from all over the U.S. and each individual showed signs of dementia or mild cognitive decline.

Notably, Americans living in regions known to have lots of air pollution were 10 percent more likely to show amyloid plaques in their PET scans.

If we apply these results to the entire U.S. population and the roughly 5.8 million people over the age of 65 diagnosed with Alzheimer’s today, smog exposure may be involved in tens of thousands of those diagnoses.

“This study provides additional evidence to a growing and convergent literature, ranging from animal models to epidemiological studies, that suggests air pollution is a significant risk factor for Alzheimer’s disease and dementia,” says senior study author Gil Rabinovici, MD in a university release.

A significant number of participants showed no signs of amyloid plaque buildup (40%), indicating the cognitive issues seen in those participants may be due to other problems like frontotemporal or vascular dementias.

Dirtier air has dire consequences

To measure air pollution levels across the nation, researchers analyzed data on round-level ozone and PM2.5 readings (particulate matter in the air with a diameter less than 2.5 micrometers) provided by the Environmental Protection Agency. Using that information, the team divided different areas and regions into “quartiles” depending on PM2.5 concentration levels. Sure enough, the greater the local air pollution, the greater the probability of amyloid plaque buildup.

“Exposure in our daily lives to PM2.5, even at levels that would be considered normal, could contribute to induce a chronic inflammatory response,” notes first study author Leonardo Iaccarino, PhD. “Over time, this could impact brain health in a number of ways, including contributing to an accumulation of amyloid plaques.”

Troublingly, particulate matter levels don’t even have to be all that high to impact amyloid plaque buildup. Researchers say the annual average in San Francisco, for example, appears to be enough to make a cognitive difference.

“I think it’s very appropriate that air pollution has been added to the modifiable risk factors highlighted by the Lancet Commission on dementia,” Dr. Rabinovici concludes.

The study is published in JAMA Neurology.