The Link Between Wildfire Smoke and Higher Dementia Risk

Parts of California, Oregon and Montana have been hit by several massive wildfires, including the Park Fire in Northern California, the fifth-largest in state history, and air pollution has reached unhealthy levels.

Smoke from wildfires can travel hundreds, even thousands, of miles, making it a danger to people nearby as well as those far away.

The fine particles in the smoke are not only bad for your lungs, but a series of studies in recent years have shown that they also have a negative impact on brain health, increasing the risk of dementia, cognitive impairment and mental health problems.

“Much of the research on wildfire smoke has historically focused on the lungs and the heart,” said Stephanie Cleland, an assistant professor at Simon Fraser University who studies the health effects of wildfire smoke. “It's only recently that we've seen a focus on cognitive function and brain health.”

Adding to this body of evidence is a study presented Monday at the Alzheimer's Association International Conference suggesting that wildfire smoke may increase the likelihood of a dementia diagnosis.

The study analyzed health records of more than 1.2 million Southern California adults aged 60 and older from 2009 to 2019.

The researchers looked at where people lived and their exposure to fine particles from wildfire smoke and other pollutants, and found that for every extra microgram per cubic meter of fine particulate matter from smoke that participants were exposed to over a three-year period, their odds of developing dementia increased by 21%.

In contrast, a similar increase in exposure to fine particulate matter from other sources, such as cars and factories, was associated with a 3% increased odds of developing dementia.

Study author Dr. Holly Elser, a neurology resident at the Hospital of the University of Pennsylvania, said the evidence is still preliminary but supports that chronic exposure to wildfire smoke contributes to cognitive decline.

But, she said, “the threshold at which wildfire smoke begins to pose a risk to dementia is unclear.”

a A study published in August Similarly, higher exposure to fine particulate matter from a variety of sources, including wildfires, was also found to be associated with higher incidence of dementia.

Climate change is making wildfires more frequent and more intense, and it is also increasing people's exposure to smoke. Between 2003 and 2023, the frequency of major wildfires is expected to more than double, Recent research has shown that.

Scientists believe that wildfire smoke affects the brain because the tiny particles it contains can penetrate the barrier between the bloodstream and the brain, causing inflammation in the central nervous system. The particles can also travel directly from the nose to the brain, which can affect people's ability to think, learn, and remember.

Dementia isn't the only potential impact. Research in 2022 Adults who had recently been exposed to wildfire smoke performed worse on brain-training games that measure abilities such as memory, attention, flexibility, processing speed and problem-solving skills, a study has found.

“People's alertness is significantly reduced within hours to days of exposure to wildfire smoke,” said Cleland, one of the study's authors.

other A study published in the same year Exposure to wildfire smoke during the school year has been shown to lower students' test scores compared to smoke-free years.

“The more smoke you're exposed to, the worse your test scores are,” said Marshall Burke, a co-author of the study and an associate professor of global environmental policy at Stanford University. “The impact on individual students is probably pretty small, but when you add it up across students and across schools, it adds up to a pretty significant overall learning loss.”

But Mr Burke said he had doubts about the dementia study findings published this week because wildfire smoke and other pollution “cannot be equated”.

Elser acknowledged that many questions remain about how smoke affects the brain — for example, it's unclear whether smoke causes dementia in healthy people or only in those who are already at risk.

“That's a really interesting question as to whether this is creating new cases of dementia that never would have occurred before, or whether it's simply hastening the onset of clinically evident dementia,” she said.

Other questions remain about the relationship between wildfire smoke and mental health. February Survey Exposure to smoke from wildfires in the western United States has been linked to increased emergency room visits for anxiety. depression and Psychosis like schizophrenia.

Elser said wildfire smoke can change the neurochemistry in people's brains, which can lead to depression and anxiety, but it's also possible that the anxiety and stress of experiencing and living through a wildfire can independently lead to mental health issues.

Other health effects of wildfire smoke are fairly well understood: Scientists have known for decades that inhaling smoke particles can travel deep into the lungs or enter the bloodstream, increasing the risk of asthma, stroke, heart attack, lung cancer, and low birth weight in newborns.

Cleland said it's not just people in fire-prone areas of the U.S. who have to worry about these risks, as the Canadian wildfires that blanketed parts of the Midwest and Northeast in smoke last summer showed.

“Last summer completely changed our discussion of who is exposed to wildfire smoke,” she says. “Oregon, California, Washington and British Columbia are actually getting a lot of wildfire smoke, but that doesn't mean places like the northeastern U.S. and Ontario aren't affected.”

To reduce exposure to wildfire smoke, experts recommend that people living in areas with high levels of wildfire smoke: Air Quality Index Reading If your count is over 100, avoid outdoor activities, close all windows, run indoor air purifiers, and wear an N95 mask if you must go out.