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two bikes sit alongside a biking trail with smoke and haze in the distance

The weather app on my phone the other day suggested in rather earnest fashion that I stay indoors. The air-quality index had clocked in at an “unhealthy” 151, more than 100 points above what experts consider to be safe. The warning seemed fairly unequivocal: “Everyone may begin to experience health effects. Members of sensitive groups may experience more serious health effects.”

I like to think of myself as a nonmember of these “sensitive groups” and generally ignore such alerts. Pedaling to the office later that morning, though, I couldn’t help noticing a smoky haze had descended upon the landscape, a product of wildfires up north and who knows what else. This can’t be good for the lungs, I pondered as I huffed up the hill.

It’s probably not doing my aging brain any favors, either.

The science is pretty clear about the many ways in which air pollution damages our cardiovascular and respiratory systems, but I was struck last week by research presented at the annual Alzheimer’s Association International Conference that solidifies the connection between our foul air and dementia.

First the bad news: A team of researchers from the University of Washington tracked levels of common air pollutants — fine particulate matter (PM2.5), large particulate matter (PM10), and nitrogen dioxide (NO2) — enveloping the residences of more than 3,000 study participants for up to 20 years. These volunteers displayed no signs of dementia at the outset of the study, but after as little as eight years, blood tests revealed the presence of troublesome amounts of amyloid plaque, a reliable marker of the disease.

“Our findings suggest that air pollution may be an important factor in the development of dementia,” notes lead study author Christina Park, a doctoral student in the department of epidemiology. “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.”

Two other studies offer some hope on that front. Using data from the Women’s Health Initiative Memory Study, Xinhui Wang, PhD, and his colleagues at the University of Southern California analyzed dementia development among a group of women aged 74 to 92 along with air pollution levels in their neighborhoods over a 10-year period. Those who lived in areas where air quality — specifically PM2.5 and NO2 levels — improved saw their risk of developing the disease drop by as much as 26 percent.

Noemie Letellier, PhD, and her University of California, San Diego research team reported similar results after reviewing a large French study involving 7,000 seniors. Allowing for socio-demographic, health behaviors, and hereditary factors, they found that every microgram reduction in PM2.5 levels reduced the risk of all-cause dementia by 15 percent and the risk of Alzheimer’s by 17 percent.

“These data, for the first time, highlight the beneficial effects of reduced air pollution on the incidence of dementia in older adults,” Letellier explains. “The findings have important implications to reinforce air quality standards to promote healthy aging. In the context of climate change, massive urbanization, and worldwide population aging, it is crucial to accurately evaluate the influence of air pollution change on incident dementia to identify and recommend effective prevention strategies.”

All these studies still await peer reviewal and publication, so it’s probably a good idea to temper any expectations that their findings will spark some urgency among public-health officials still struggling to contain a resurgent pandemic. Indeed, given the number of lawmakers at the federal and state level who continue to deny the existence of human-driven climate change, I’m not going to hold my breath waiting for some meaningful legislative or regulatory action to save our aging brains.

I’ll save that gambit for the next time I’m biking to the office.

Craig Cox
Craig Cox

Craig Cox is an Experience Life deputy editor who explores the joys and challenges of healthy aging.

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