Does the particle size of air pollution affect the risk of death from stroke?

Living in areas with more air pollution is associated with an increased risk of death from stroke in hospitals, and the risk varies depending on the size of the air pollution particles, according to a new study published in the online edition of May 25, 2022. with Neurology.

The study looked at three sizes of airborne particulate matter. Solid particles consist of liquid or solid substances suspended in air. Submicron Solid Particles, PM₁, diameter less than one micron and includes soot and smog. Fine Particles, PM_2.5, has a diameter of less than 2.5 microns and includes coal ash. Inhalable Solids, PM₁₀has a diameter of less than 10 microns and includes cement dust.

“Previously, air pollution was associated with greater risk strokeand stroke is the leading cause of death worldwide, “said study author Hualien Lin, Ph.D., of Sun Yat-sen University in Guangzhou, China. ».

For the study, scientists conducted a survey electronic medical records in China find more than 3.1 million hospitalized for stroke, both ischemic stroke caused by blood clots and hemorrhagic stroke caused by bleeding in the brain. The average age of the participants was 67 years. Of this group, 32,140 people, or 1%, died of stroke during hospitalization.

The researchers identified individual levels of exposure to air pollution for each participant, using their home addresses and a source of air pollution data that captures daily concentrations of different types of particulate matter. The researchers then calculated a seven-day exposure to polluted air immediately before hospitalization due to stroke, which was 31.38 micrograms per cubic meter (μg / m).³) PM₁45.43 μg / m³ the Prime Minister_2.5 and 78.75 μg / m³ the Prime Minister₁₀. They also calculated the average daily human exposure to particulate matter in the year before hospitalization was 32.98 μg / m³ the Prime Minister₁49.08 μg / m³ the Prime Minister_2.5 and 87.32 μg / m³ the Prime Minister₁₀.

After adjusting for factors such as age, gender, socio-economic statusdiabetes and high blood pressurethe researchers found every 10 mcg / m³ The increase in the mean annual exposure to particulate matter was associated with an increased risk of death from stroke during hospitalization, with a 24% higher risk of exposure to PM₁11% higher risk of PM exposure_2.5and 9% higher risk of PM exposure₁₀. The mean seven-day exposure to particulate matter included a 6% increase in the risk of PM exposure₁the risk of PM exposure increases by 4%._2.5and a 3% increased risk of PM exposure₁₀.

The risks were stronger in people with ischemic stroke than in people with hemorrhagic stroke. The greatest risk of death from stroke was in people with ischemic stroke and exposure to finer air pollution particles, PM₁.

However, researchers also found a decrease in PM₁₀ will have the greatest impact on reducing overall stroke mortality by reducing hospital deaths by 10% with short-term exposure and by 21% with long-term exposure.

Lynn said it’s important to note that the results of the study don’t prove that air pollution causes death from stroke, they only show a link.

“Our study involves measuring PM1, which can be small enough to be inhaled deeply into the lungs, to go through lung tissueand circulating in the bloodstream, “Lynn said.” Gaining a deeper understanding of everyone’s risk factors solid particles the size and magnitude of their possible consequences can help reduce the number of deaths and improve outcomes for people with stroke. ”

A limitation of the study was that the results were not adjusted for human smoking status or stroke severity. The researchers also investigated the effects of air pollution only at the person’s current residence and not at previous habitats.