Researchers say their studies on air pollution and cognitive decline — one involving humans and one with mice — provide evidence that cleaner air may reduce risk for Alzheimer’s and other dementias.

Cars and factories produce a fine particulate known as PM2.5 that USC-led studies have linked to memory loss and Alzheimer’s disease. Smaller than the width of a human hair, these tiny particles pose a big problem. Once inhaled, they pass directly from the nose up and into the brain, beyond the blood-brain barrier that normally protects the brain from dust or other invaders.

In a research letter published today in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, the USC researchers described how their labs each independently reported indications of recent decreases in neurotoxicity (damage to the brain or nervous system caused by exposure to toxic substances) of PM2.5 air pollution in humans and mice.

University Professor Caleb Finch and associate professor of gerontology and sociology Jennifer Ailshire, both with the USC Leonard Davis School of Gerontology, focused on PM2.5 pollution. Long-term exposure to PM2.5 has been linked to premature death, particularly in people with chronic heart or lung diseases.

Ailshire’s research, published earlier this year in the Journal of Alzheimer’s Disease, showed a strong association between cognitive deficits and air pollution among people with lower levels of education in 2004.

Based on data from the nationwide Health and Retirement Study, her work showed that, when exposed to PM2.5, adults 65 and older who had fewer than eight years of education faced a greater risk of cognitive impairment. But one decade later, Ailshire found no such association for study participants.

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Materials provided by University of Southern California. Original written by Jenesse Miller. Note: Content may be edited for style and length.