Exposure to wildfire smoke linked to risk of dementia

MONDAY, Nov. 25, 2024 (HealthDay News) — People in Southern California with relatively frequent exposure to wildfire smoke over a decade also had a significantly higher risk of developing dementia, a new study warns.

In fact, the researchers note, the fine particle pollution created by these fires is more closely linked to brain problems than similar pollutants from factories and car exhaust.

Over the long term, each one microgram per square meter increase in air pollution caused by bushfires “was associated with an 18 percent increase in the likelihood of a dementia diagnosis,” the team led by Joan Casey concluded. She is an assistant professor in the Department of Environmental and Occupational Health at the University of Washington in Seattle.

The new study examined health data from more than 1.2 million members of the Kaiser Permanente Southern California health system. Participants were followed from 2008 to 2019.

Casey’s team linked changes in each participant’s neurological health to exposure to local wildfires. The number of fires in Southern California has increased in recent years due to climate change.

The researchers specifically looked at an airborne pollutant called PM 2.5. It is a combustion product that is so small that it can penetrate deep into the lungs and is believed to even be able to overcome the protective barrier of the brain and blood.

Studies of PM 2.5 from industry or automobiles have long shown that it is “associated with the onset of dementia,” the researchers noted.

Will PM 2.5 emissions from wildfires be different?

It may be much more harmful to the brain than other forms of PM 2.5, according to the study.

The researchers calculated that while long-term exposure to wildfire particles increased the likelihood of developing dementia by 18 percent, similar exposure to PM 2.5 from other sources increased people’s risk by only 1 percent.

Of the more than 1.2 million Californians covered in the study, certain groups were found to be at particular risk.

People who were under 75 when they took part in the study were more likely to suffer smoking-related brain damage than older people, and people living in poorer areas also faced a higher risk of developing dementia associated with smoke from forest fires.

Why can poverty make a difference?

As the researchers explained, people are advised to stay home whenever wildfire smoke clouds the air, but poorer households may have “lower quality housing (which) may increase smoke penetration.” They also may not be able to afford expensive air filtration devices, Casey’s team noted.

Poverty and race are often linked, so the fact that the link between wildfire smoke and dementia was stronger among blacks and Hispanics compared to whites was not surprising, the researchers added.

Because of warmer and drier conditions caused by climate change, “wildfires, once rare and geographically limited, now regularly affect the U.S. population,” Casey’s team noted.

Helping prevent these fires and better protect residents from smoke if they occur “could reduce the number of dementia diagnoses” in the coming years, they said.

The study appears in the November 25 issue of JAMA Neurology.

Additional information

Learn more about the effects of air pollution on the brain at Harvard University.

SOURCE: JAMA Neurology, November 25, 2024.