Long-term exposure to wildfire smoke linked to increased risk of dementia: study

Long-term exposure to wildfire smoke could increase the risk of developing dementia even more than exposure to other sources of air pollution, according to a new study.

In the study, published last week in the journal JAMA Neurology, researchers examined a cohort of more than 1.2 million people over the age of 60 who lived in Southern California between 2008 and 2019. They tracked the incidence of dementia in the cohort and compared it to the average concentration of particulate matter, also known as PM2.5, in the air due to wildfires in the region.

They found that when the average wildfire PM2.5 concentration increased by just one microgram per cubic meter of air over three years, the likelihood of a dementia diagnosis increased by 18 percent.

The same increase in levels of PM2.5 not caused by wildfires was associated with only a three percent increase in the likelihood of a dementia diagnosis.

Although previous research has linked long-term exposure to air pollution to a higher risk of dementia, the effects of specific sources of air pollution have been less researched.

“You see a greater impact of PM2.5 from wildfires than from other sources,” said Scott Weichenthal, an associate professor in the department of epidemiology, biostatistics and occupational medicine at McGill University in Montreal. He was not involved in the study.

“This is important because we need to start paying more attention to the type of particles that are in the air and not just how much mass they have, because chemical composition also plays a really important role in health Effects.”

How smoke can reach the brain

Particulate matter is tiny airborne particles found in smoke and fumes that are less than 2.5 micrometers in size and can travel deep into the lungs when inhaled.

Wildfire smoke can contain a dangerous cocktail of chemicals from burned homes, vehicles and plastics, Weichenthal said. And unlike smog, which is a constant source of air pollution, smoke from wildfires leads to massive spikes in PM2.5 concentrations in the air – which can affect not just the lungs, but the entire body.

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When the body encounters foreign particles, it reacts and puts the lungs into a “heightened state of inflammation,” which can spread to other organs through inflammatory cells in the bloodstream, said Michael Brauer, a professor at the School of Population and Public Health at the University of British Columbia in Vancouver.

This is the leading theory about how long-term exposure to air pollution can affect the brain, he told CBC News, although scientists are still unsure about the mechanisms.

Brauer, who was not involved in the study but has previously examined the connection between PM2.5 and dementia in his research, said air pollution has strong effects on the cardiovascular system and possibly also on blood flow to the brain.

How to minimize exposure

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Air filtration systems like HEPA filters go a long way toward reducing long-term exposure, Weichenthal said. On days with poor air quality during wildfire season, wearing a KN95 or N95 mask also minimizes risk while outdoors.

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But last week’s study found that the link between long-term exposure to wildfire smoke and dementia is stronger among people living in high-poverty areas – where people may not be able to afford air filters or have access to air quality warnings or can stay home from work Avoid going outdoors on days when there is heavy smoke.

It is a sign that society needs to switch to more climate infrastructure, said Brauer.

“For a fraction of the cost of treating a person in the emergency room, you’re paying for a portable air purifier in their home, or we’re equipping every school with air filtration… And actually over…” In the long run, we’ll probably make money save just because of … the extreme costs of actually treating people.”

When the researchers examined the data more closely, they also found that the sharp increase in dementia risk associated with PM 2.5 wildfires primarily affected people between the ages of 60 and 75.

This could be because younger seniors are more likely to spend time outdoors and have longer-term exposure to wildfire smoke, researchers suggested.

People over 75 who have not yet developed dementia may also have been “least vulnerable” to developing dementia because the disease does not affect all seniors, Weichenthal said.

The health risk from forest fires continues to increase

The health effects of wildfire smoke are a growing concern as climate change pushes extreme weather events to new levels. Wildfires in Canada have increased in size and intensity, with the area burned increasing significantly decade after decade over the past 50 years. In 2023, Canada experienced the most devastating wildfire season ever: more than 15 million hectares of land burned.

According to Brauer, the increase in baseline exposure over time is most concerning because these long-term health effects will continue to add up.

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When he was younger, Brauer said, Vancouver experienced about one day of heavy smoke from wildfires every decade, “back then it was about every three years, and now it’s at least a week every summer.”

“Think about a child who is now an adult. It’s 10 years old. It has had that every year of its life, and it will have that for the next 50 or 60 years.”

With wildfires expected to get worse over time, scientists are working to keep up. McGill University launched the McGill Center for Climate Change and Health in November to try to address the problems that climate change will bring.

“This type of frequency and intensity of wildfires is likely to be with us for the rest of our lives,” said Weichenthal, the center’s deputy director. “So we need to think about what we can do to adapt and take steps to reduce our exposures, while recognizing that we are unlikely to be able to prevent them.”