Vehicle exhaust was cut dramatically. Dust particles flying from construction sites ceased. Star gazers enjoyed a clear view of the constellations and, at long last, fresh air wafted through open windows in cities around the world.

The first pandemic lockdown brought into sharp focus just how much air pollution city dwellers live with, and the incredible difference it makes when that pollution is reduced.

While long-term air pollution is linked to cognitive decline and dementia, what happens when air quality improves? Will this benefit cognitive function and reduce dementia risk?

The results from several long-term studies are in…

Toxic air comes from many sources. Two of the most dangerous are particulate matter 2.5 (PM2.5), which generally comes from fuel combustion, and nitrogen oxide (NO2), which is formed from emissions from cars, trucks and buses, power plants, and off-road equipment.

More than 50 years have passed since the Clean Air Act was signed into law, and together, with modern pollution control technologies, emissions have dropped considerably.

How has improved air quality affected brain health? A team of researchers at the University of Southern California (USC) investigated.

Better Air Quality Means a Sharper Brain 

The USC researchers followed American women aged 74 to 92, who were initially free from dementia in 2008 when the study began. Every year for the next ten years the women took comprehensive cognitive tests. Meanwhile, researchers used their home addresses to estimate pollution levels from a decade before the study began (1998) to 2018. That’s 20 years of data on air pollution.

Fortunately, pollution levels fell overall for every participant during that time. What’s more, for those living in areas that saw the greatest decline in PM2.5 and NO2 pollutants, their risk of dementia fell by 14 percent and 26 percent respectively. In fact, these reductions lowered this age group’s dementia risk to a level seen in women two to three years younger.

In addition, the study participants experienced a slower decline in overall cognitive function and memory. Again, this was like the decline seen in women one to two years younger. Best of all, these memory benefits were seen in study participants regardless of age, education, geographic region or whether they had cardiovascular disease.

Lead researcher Xinhui Wang said the study “… provides new evidence that by improving the quality of air we may be able to significantly reduce risk of cognitive decline and dementia. The possible benefits found in our studies extended across a variety of cognitive abilities, suggesting a positive impact on multiple underlying brain regions.”

Dementia Risk Falls Sharply as Pollutants Decline 

Another study involving over 7,000 seniors living in France found similar results. Between 1990 and 2000 researchers documented how participants’ exposure to levels of PM2.5 fell as air quality improved. The team concluded that for every microgram decrease of gaseous pollutant per cubic meter of air (µg/m3), there was a 15 percent decrease in dementia risk and a 17 percent decrease in Alzheimer’s risk.

Noemie Letellier from the University of California, San Diego, said, “These data, for the first time, highlight the beneficial effects of reduced air pollution on the incidence of dementia in older adults.

“The findings have important implications to reinforce air quality standards to promote healthy aging.”

Long-Term Pollutant Exposure Linked to Higher Blood Amyloid 

To date both short-term animal and human studies link air pollution to increased production of amyloid-beta brain plaques. However, little is known about the effects of long-term exposure to air pollution on brain plaques.

So, researchers from the University of Washington examined over 3,000 Americans who were dementia-free when the study began. They evaluated levels of NO2, PM2.5 and PM10 (a larger particle) at participants’ homes for up to 20 years before drawing blood to measure Aβ1-40, a major component of plaques.

Researchers found a strong link between those participants with the longest exposure time to all three pollutants and increased levels of Aβ1-40. These are some of the first human data to show that people exposed to air pollution for longer periods of time have higher Aβ1-40 levels in the blood.

Christina Park, who led the group, said, “Many other factors that impact dementia are not changeable, but reductions in exposure to air pollution may be associated with a lower risk of dementia.”

My Takeaway 

The research is another good argument for country living. And if you can’t get out of your large metropolitan area—or don’t want to—then I recommend buying several high-quality air purifiers for your home and clean those purifiers regularly. Air purifiers can help cut down on your exposure to damaging air pollutants so they can’t negatively impact your memory.


  1. https://alz.org/aaic/releases_2021/air-pollution-dementia-risk.asp 

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