New evidence—funded by Cure Alzheimer’s Fund (CAF) and others—has emerged suggesting a strong connection between air pollution and Alzheimer’s disease. “These findings underscore the complexity of this disease,” says CAF President and CEO Tim Armour, “and emphasize the need for a comprehensive approach to stop it.”
While Alzheimer’s researchers have theorized for a more than a generation that environment and lifestyle play a significant role in the development of Alzheimer’s, only now are they learning about pollution’s important role. “In the last five years,” said University of Southern California gerontologist Caleb Finch, Ph.D., “it’s become very clear to me and others that air pollution is a likely risk factor in Alzheimer’s, as well as in other changes in brain aging that slow our cognitive processes. This is a very large issue that we face globally.”
Thankfully, it’s also an issue researchers are beginning to address seriously. “There are now more than ten labs working on this around the world,” says Finch. “Five years ago, there were just a few. The topic is catching up to the recognition that it merits.”
Finch is helping to lead the way. A widely acclaimed biomedical gerontologist who specializes in environmental effects on brain aging, he has received numerous scientific awards and has authored 500 research studies, as well as several major books on aging. In 1984, Finch was the founding director of the University of Southern California’s Alzheimer Disease Research Center, funded by the National Institute on Aging. He joined Cure Alzheimer’s Fund’s Scientific Advisory Board in 2014.
Finch’s recent attention to pollution was stimulated by emerging epidemiological studies from USC and elsewhere showing the following:
- A strong association between urban pollution and shorter life expectancy: about 1.5 years shorter in the U.S. and five years shorter in China.
- A direct correlation between urban pollution and a dangerous thickening of the walls of the carotid artery, limiting blood flow to the brain.
- A strong connection between air pollution and inflammation in parts of the brain affected by Alzheimer’s disease.
- A direct correlation between urban pollution and decreases in verbal learning, logical reasoning and memory, and executive function in middle-aged and older adults, both in the Los Angeles area and across the U.S.
From all of this, Finch concludes, “It looks to me that air pollution contributes to at least five percent of Alzheimer’s, and it may be much more.”
His own research on pollution’s effect on aging has been spurred in two ways by a 2014 CAF research grant to examine the effect of nano-sized particulate matter (derived mostly from automobile traffic in urban environments) on the creation of Abeta in mice. Small particle air pollution is particularly worrisome, because that is the material that finds its way into the bloodstream. “We’re not worried about the particles larger than 2.5 microns, such as fireplace smoke,” Finch explains. “Those are trapped in the upper airways. The ones that we’re really concerned about are invisible to the human eye — smaller than 2.5 microns. They penetrate deeply into the lung, and they reach the brain.”
That 2014 CAF-funded project, says Finch, developed in conjunction with his USC associate Mafalda Cacciottolo, later led to a substantial grant from the National Institutes of Health. Together, their research established strong evidence that urban pollution is contributing to a toxic increase in Abeta, which in turn leads to the development of Alzheimer’s.
“This sort of leveraging of small, privately funded projects into much larger, public-funded research is central to the Cure Alzheimer’s Fund mission,” says Armour.
While the news about air pollution’s neurotoxicity is stunning and worrisome, there is some reassuring news. These nanoparticles though abundant around the world, are on the decline in some nations. The U.S., for example, has seen a 35 percent decrease in the concentration of small airborne particles from 2000 to 2014. “Fifteen years ago, the bulk of the country was over the EPA safety standard,” Finch says. “Now, more than half of the country is under the safety standard. So we’re making progress.”
“This is a key piece of the puzzle,” says CAF Research Consortium Chair Rudy Tanzi, Ph.D. “Alzheimer’s emerges more than a decade before symptoms begin, with the over-accumulation of Abeta in the brain. As we aggressively move toward therapies to control that process, we need to expand our understanding of the contributing factors.”
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