A possible link between dementia and air pollution

In the past decade, a growing body of research has shown that air pollution damages the brains of older adults, and contributes to cognitive decline and dementia. What wasn’t clear was whether improving air quality would benefit brain health.

Two studies published this year by researchers at six universities and the National Institute on Aging provide the first evidence of these benefits in older adults.

One report, published in Proceedings of the National Academy of Sciences, It found that the risk of dementia decreased significantly in women aged 74 and older after a decade-long reduction in two types of air pollution: nitrogen dioxide, a gaseous by-product of emissions from automobiles, industrial sources, and natural events such as wildfires; And the fine particlesa mixture of very small solids and liquids resulting from similar sources.

second report in MEDICINE PLOS, drawing on the same sample of more than 2,200 elderly women, found that lower levels of these pollutants were associated with a slower rate of cognitive decline. In areas where air quality improvement was most pronounced, the rate of cognitive decline was delayed by up to 1.6 years, depending on the test.

The report says that the fittest are 33% less likely to develop Alzheimer’s disease

Both studies are national in scope and consider other factors that could influence outcomes, such as participants’ socioeconomic status, neighborhood characteristics, pre-existing medical conditions and lifestyle choices such as smoking.

What might explain their results?

“We believe that when air pollution levels are reduced, the brain is more able to recover” from previous environmental insults, said Shenhui Wang, associate professor of neuroscience research at the University of Southern California School of Medicine. She suggested that the hypothesis needs further study in animal studies and through brain imaging.

There are many theories about how air pollution affects the brain. Tiny particles–a human hair at least 30 times larger than the largest particle–may travel from the nasal cavities to the brain via the olfactory system, putting the brain’s immune system on high alert. Or, pollutants may lodge in the lungs, causing an inflammatory response that spreads to the brain.

Also, pollutants can damage the cardiovascular system, which is essential for brain health. (The links between air pollution, stroke and heart disease are firm.) or fine particles can cross the blood-brain barrier, causing direct damage. Oxidative stress may occur, resulting in the release of free radicals that damage cells and tissues.

Older people are especially at risk To the harmful effects of air pollution due to reduced lung capacity and the potential for pollutants to exacerbate conditions such as respiratory and heart disease. Also, the effects of air pollution accumulate over timeThe longer people live, the greater the risks they may face.

However, the recognition of the potential cognitive consequences of air pollution is relatively recent.

the first national study The link between air pollution and cognition was published in a diverse sample of older men and women in 2014. It found that older people who lived in areas with high levels of fine particulates were more likely to have cognitive problems than people who lived in less polluted areas. .

Another studyTwo years later, she extended these findings by reporting an amplification of the cognitive effects of air pollution in older adults who live in deprived neighborhoods where pollution levels tend to be higher. The authors wrote that the chronic stress experienced by the inhabitants of these neighborhoods may “increase the rate of neuronal damage due to toxic challenges.”

The researchers said that air pollution is only one of many factors that influence cognitive decline and dementia, and findings of this kind establish associations rather than causation.

Is my memory persistent or is it just normal aging?

Recent research indicates that older adults’ cognition is affected even when exposures are lower Standards set by the Environmental Protection Agency.

“With older adults, there really is no level at which air pollution is safe,” said Jennifer Elshire, associate professor of gerontology and sociology at the University of Southern California.

“It is important to continue to lower the standards for these pollutants,” said Antonella Zanopetti, principal research scientist for environmental health at Harvard University’s T.H. Chan School of Public Health. She and her colleagues won a grant from the National Institute on Aging to study how air pollution affects the risk of Alzheimer’s disease and related dementia among healthcare recipients. In 2019, her work showed that higher levels of fine particles are associated with more hospitalizations among older adults with dementia — a sign of disease progression.

Last year, in One of the largest American studies to dateIn this study, a group of researchers examined the relationship between long-term exposure to particulate matter and nitrogen dioxide among 12 million Medicare recipients diagnosed with Alzheimer’s disease and other forms of dementia. The researchers concluded that exposure to high levels of these pollutants appears to accelerate cognitive decline that was already relatively advanced, leading to increased diagnoses.

In addition to population-level studies, nearly 20 scientific laboratories around the world study how air pollution contributes to dementia in animals. At the University of Southern California, Caleb Finch, a professor who studies the neurobiology of aging, is a co-principal investigator in a five-year, $11.5 million grant from the National Institute on Aging to study. How urban air is polluted It affects the risk of developing dementia and accelerating brain aging.

Among the questions to be answered, Finch said, are which areas of the brain seem to be most vulnerable to air pollutants? When are people most at risk? How long does the damage last? Is healing possible? Do lifestyle interventions such as diet and exercise help?

“The key point is that we now recognize that Alzheimer’s disease is very sensitive to environmental influences, including air pollution,” Finch said.

Realizing this, The Lancet Committee on Dementia Prevention, Intervention and Care In 2020, air pollution added to the list of modifiable risk factors for dementia, and it was estimated that up to 40 percent of dementia cases worldwide could be prevented or delayed if these risk factors were addressed.

For her part, Elshire is optimistic that public policies can make a difference. She noted that from 2000 to 2019, average annual particulate matter pollution fell by 43 percent nationwide due to efforts to improve air quality. “I am very optimistic that these efforts will continue,” she told me.

I suffer from incurable cancer. A houseplant that helps me face the yard.

What can seniors worried about air pollution do on their own?

On hot days, take a walk in the morning instead of the afternoon, when ozone levels are highest, said Anthony Gerber, MD, a pulmonologist at National Jewish Health, a Denver medical center that specializes in respiratory conditions. Ozone is a poisonous gasIt forms when different chemicals react with sunlight and heat.

If you live in the western United States, where wildfires spreading fine particulates are becoming more common, “wear a KN95 mask” on days when fires affect air quality in your area, Gerber said.

Also, if you can buy air purifiers for your home, he advised, noting that fine particles can get into homes that aren’t well-enclosed.

To check air quality levels in your area, go to AirNow.govElshire said. “If it was a very risky day, it might not be the day to go out and do heavy work in the yard,” she said.

But don’t stay indoors all the time and become overly self-protective.

“It’s really important for the elderly to get out and exercise,” Gerber said. “We don’t want older people to end up sick because they breathe in a lot of particulates, but we don’t want them to become inactive and be stuck at home either.”

This article was produced by Kaiser Health NewsAnd the A program for the Kaiser Family Foundation, a nonprofit organization that provides information on the nation’s health issues.

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