Research has suggested that air pollution impacts the brains of older adults and contributes to cognitive decline and dementia—but until now, no researchers have linked improved air quality to better cognition. Writing for Kaiser Health News, Judith Graham explains how two new studies have found the first evidence that better air quality could lead to healthier brains in older adults.
The two new studies, both published in 2022, used the same sample of over 2,200 older women for their analyses. Both were also conducted nationally and factored in variables that could impact results, including socioeconomic status, neighborhood traits, preexisting medical conditions, and lifestyle choices.
The first study, published in the Proceedings of the National Academy of Sciences, found that a 10-year reduction in two types of air pollution—nitrogen dioxide and fine particulate matter—lead to a significant decline in the risk of dementia among women 74 and older..
In the second study, published in PLOS Medicine, researchers determined that decreased levels of nitrogen dioxide and fine particulate matter were associated with a slowed rate of cognitive decline. According to the researchers, the rate of cognitive decline slowed by up to 1.6 years in areas with the most significant air quality improvements.
"We think that when air pollution levels are reduced, the brain is better able to recover" from previous environmental impacts, said Xinhui Wang, an assistant professor of research neurology at the University of Southern California's (USC) medical school.
According to Wang, the hypothesis must be further examined through brain imaging and animal studies.
There are several theories about the impact air pollution has on the brain. For instance, tiny particles can travel from the nasal cavities to the brain, alerting the brain's immune system. Pollutants can also become lodged in a person's lungs, triggering an inflammatory response that spreads to the brain.
In particular, older adults are vulnerable to the harmful effects of air pollution because of their reduced lung capacity. Pollutants also have the potential to worsen existing conditions, including respiratory illnesses and heart disease.
"With older adults, there really is no level at which air pollution is safe," said Jennifer Ailshire, an associate professor of gerontology and sociology at USC.
"It's important to keep on reducing the standards for these pollutants," said Antonella Zanobetti, principal research scientist for environmental health at Harvard University's T.H. Chan School of Public Health.
"The main point is we now realize that Alzheimer's disease is very sensitive to environmental effects, including air pollution," said Caleb Finch, a USC professor who studies the neurobiology of aging.
According to Anthony Gerber, a pulmonologist at National Jewish Health, older adults should go for walks or conduct other outdoor exercise in the morning instead of the afternoon when ozone levels are higher.
For those who live in the western portion of the United States where wildfires have become more common, Gerber recommends wearing a high-quality mask and using air purifiers in the home.
To check local air quality levels, Ailshire recommends visiting AirNow.gov. However, it's important not to become too overly self-protective. "It's really important for older adults to be outside and exercise," Gerber said. "We don't want seniors to end up sick because they're breathing lots of particulates, but we don’t want them to become inactive and stuck at home either." (Graham, Kaiser Health News, 9/20)
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