December 18, 2024
A growing number of studies have implicated air pollution as a risk factor for the onset of dementia. Now a new report found that one type of air pollution may be particularly bad for the brain: wildfire smoke.
Researchers analyzed the health records of more than 1.2 million people aged 60 and older who were living in southern California between 2008 and 2019. All were free of dementia at the start of the study period. Over the ensuing decade, some developed Alzheimer’s disease or other forms of dementia.
The researchers also estimated residents’ exposure to an especially hazardous form of air pollution called fine particulate matter, or PM2.5. These tiny pollutant particles, smaller than 2.5 micrometers in diameter or 30 times smaller than the width of an average human hair, can be breathed in and make their way into the brain. The research team looked at exposure to PM2.5 both from wildfire smoke as well as other sources of pollution such as traffic exhaust and factory chimneys over various three-year periods.
They found that for every 1 microgram per cubic meter increase in the three-year average PM2.5 concentration from wildfire smoke, the odds of a dementia diagnosis increased by 18 percent. Exposure to non-wildfire PM2.5 also increased a person’s risk of dementia, but to a much lesser degree. Risk was highest for those who were younger at the start of the study period.
Risks from wildfire pollutants were particularly pronounced in low-income areas. The authors say that in such areas, lower-quality housing may allow more smoke to enter people’s homes. Families may also be less able to afford air filtration systems that can help to lower indoor pollutant levels. The findings were published in JAMA Neurology.
“There have been studies that have found total PM2.5 is related to people developing dementia, but no one had looked specifically at wildfire PM2.5,” said Joan Casey, the senior author of the study and assistant professor in the Department of Environmental and Occupational Health Sciences at the University of Washington, Seattle. “Wildfire smoke is a different animal, in that it’s much spikier. There are many days where there’s no wildfire smoke, and there are some days where exposure is really, really extreme.”
“One microgram per meter cubed might sound fairly small, but we have to think about how people are exposed to wildfire smoke,” Dr. Casey said. “Most days they aren’t exposed at all, so this might represent a few days of exposure at a concentration of something like 300 micrograms per cubic meter, where the AQI is over 200 in someone’s community. When you think about it, it’s actually a few really severe wildfire smoke days that might translate into increased risk.”
The Environmental Protection Agency defines 12 micrograms of PM2.5 per cubic meter as a “safe” threshold, the maximum for protecting the health of asthmatics, children and the elderly.
The authors caution that with rising global temperatures and increasing numbers of forest fires, the risks from wildfire smoke will grow in coming years. To help lower your risk, update your home air filtration system when possible and keep the windows closed on smoke or smog warning days. Stay inside as much as possible, and don’t exercise outdoors when air quality is poor. When heading outdoors, wear an N95 or KN95 mask when the Air Quality Index reaches 100. The current air quality near you can be found by visiting AirNow.gov and entering your ZIP code, or using popular smartphone weather apps, including The Weather Channel, Apple Weather or AccuWeather, among others.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D. Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Holly Elser, MD, PhD; Timothy B. Frankland, MA; Chen Chen, PhD; et al: “Wildfire Smoke Exposure and Incident Dementia.” JAMA Neurology, November 25, 2024
