ISTANBUL

Long-term exposure to wildfire smoke is linked to a higher risk of stroke among older adults in the US and may be associated with about 17,000 strokes each year, according to a study published Tuesday in the European Heart Journal.

The research analyzed data from about 25 million Americans aged 65 and older enrolled in Medicare between 2007 and 2018. During that period, about 2.9 million participants experienced a stroke.

Researchers used artificial intelligence models to estimate long-term exposure to wildfire-related fine particulate matter, known as PM2.5, and assessed its association with stroke risk while accounting for other pollution sources and factors such as smoking and socioeconomic status.

They found that each increase of one microgram per cubic meter in average wildfire smoke PM2.5 exposure was linked to a 1.3% rise in stroke risk. By comparison, the same increase from other pollution sources, including traffic and power plants, was associated with a 0.7% increase.

Yang Liu of Emory University’s Rollins School of Public Health, the study’s lead author, said the findings indicate wildfire smoke may pose greater risks to the brain and blood vessels than other forms of air pollution.

“This suggests wildfire smoke may be even more harmful to the brain and blood vessels than pollution from other sources,” he said. “Looking at the US as a whole, our results suggest that exposure to wildfire smoke could be responsible for around 17,000 strokes every year in this age group.”

Liu said rural and suburban populations may face higher exposure because many wildfires originate in remote areas.

The study did not identify the precise biological mechanisms involved, but said wildfire smoke can trigger inflammation and oxidative stress, processes that may damage blood vessels and promote blood clots.

Researchers also reported no clear safe threshold for smoke exposure, suggesting that even repeated moderate exposure levels could increase health risks.

In an accompanying editorial, Kai Chen of the Yale School of Public Health and a colleague said wildfire smoke has become a growing source of PM2.5 as climate change fuels more frequent and intense fires. They said the new findings add to evidence that wildfire smoke should be viewed as a long-term public health risk rather than only an immediate environmental hazard.