Researchers at USC say their studies on air pollution and cognitive decline provide evidence that cleaner air may reduce the risk for Alzheimer’s and other dementia-related conditions.
USC professor Caleb Finch and associate professor of gerontology and sociology Jennifer Ailshire, both with the USC Leonard Davis School of Gerontology, described how their labs each independently reported indications of decreases in damage to the brain or nervous system caused by exposure to toxic substances in humans and mice in a research letter published Thursday in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
In the research, cars and factories were found to produce a form of pollution called PM2.5 that USC-led studies linked to memory loss and Alzheimer’s disease. Once inhaled, the PM2.5 particles pass directly from the nose to the brain, and beyond the blood-brain barrier that normally protects the brain from dust and other toxic substances.
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. 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. A decade later, Ailshire did not find the same association for study participants.
The reduction of PM2.5 over the decade was a likely factor in the findings, Ailshire said in a release.
“Improving air quality around the country has been a tremendous public health and environment policy success story. But there are signs of a reversal in these trends,” Ailshire said in the release. “Pollution levels are creeping up again and there are increasingly more large fires, which generate a significant amount of air pollution in certain parts of the country. This gives me cause for concern about future trends in improving air quality.”
Finch’s research on mice, published earlier this year in the Journal of Alzheimer’s Association, also found evidence of lower neurotoxicity of air pollution over time.
Finch and his research team have studied pollution levels at the same Los Angeles site as Ailshire’s team and their effects on mice since 2009. After 2017, the mice exposed to tiny scales of PM2.5 appeared healthier. They also showed sharp declines in a number of factors in neurotoxicity, including damage to cells and tissues.
“Our findings underscore the importance of efforts to improve air quality as well as the continued importance of demographic and experimental evaluation of air pollution neurotoxicity,” Finch said in the release.