Exposure to high levels of particle air pollution can increase your risk of death from stroke, and the risk is highest with the smallest-sized particles that can get deep into the lungs, researchers say.

“Air pollution has been previously linked to a greater risk of stroke, and stroke is a leading cause of death worldwide,” said study author Hualiang Lin of Sun Yat-sen University in Guangzhou, China.

“What is lesser known is how the different sizes of particulate matter affect that risk. Our research found that the size of air pollution particles may affect a person’s risk of dying from stroke,” Lin said in a Neurology news release. The findings were published online in the journal on May 25.

The study looked at the threat posed by three sizes of air pollution particulate matter, which consists of solids or liquids floating in the air.

Submicron particulate matter (PM1) is less than 1 micron in diameter. It includes soot and smog. Fine particulate matter (PM2.5) is less than 2.5 microns in diameter and includes fly ash from coal combustion. Respirable particulate matter (PM10), which includes cement dust, is less than 10 microns in diameter.

“Our study includes measurements of PM1, which may be small enough to be inhaled deeply into lungs, pass through lung tissue and circulate in the bloodstream,” Lin said.

“Obtaining a deeper understanding of the risk factors of all particulate matter sizes and the magnitude of their possible effects may help reduce the number of deaths and improve the outcomes for people with stroke,” he added.

The researchers examined data on more than 3.1 million hospitalizations in China for ischemic stroke caused by a blood clot and hemorrhagic stroke caused by bleeding in the brain. The average age of the patients was 67, and 1% died of stroke while hospitalized.

The researchers determined the patients’ average exposure to air pollution in the seven days before they were hospitalized for stroke as well as their average daily exposure over the previous year.

After adjusting for factors such as age, sex, socioeconomic status, diabetes and high blood pressure, the study authors concluded that each 10 micrograms per cubic centimeter of air (μg/m3) increase in annual average exposure to particulate matter was associated with an increased risk of dying of stroke while hospitalized, with a 24% greater risk for exposure to PM1, a 11% greater risk for exposure to PM2.5, and a 9% greater risk for exposure to PM10.

Seven-day average exposure to particulate matter included a 6% higher risk with exposure to PM1, a 4% increased risk with exposure to PM2.5, and a 3% increased risk with exposure to PM10.

Patients with ischemic stroke had a higher risk of death than those with hemorrhagic stroke, and those with ischemic stroke and exposure to the smallest air pollution particles (PM1) had the highest risk.

However, the researchers found that reducing exposure to PM10 would do the most to reduce stroke deaths, by 10% for short-term exposure and 21% for long-term exposure.

The findings do not prove that air pollution causes stroke deaths, they only show an association, Lin noted.

More information

For more on air pollution and health, go to the U.S. National Institute of Environmental Health Services.

SOURCE: Neurology, news release, May 25, 2022

Source: HealthDay