Air pollution linked to increase risk of death from stroke: study

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Living in areas with higher levels of air pollution is linked to a heightened risk of in-hospital death from stroke, a new study has found.

That threat also varies based on the size of the air pollution particles — with those patients who are exposed to the smallest particles and whose stroke was caused by a blood clot incurring the greatest risk of death, according to the study, published in the journal Neurology on Wednesday.

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

“What is lesser known is how the different sizes of particulate matter affect that risk,” he added. “Our research found that the size of air pollution particles may affect a person’s risk of dying from stroke.”

The researchers explored three different sizes of air pollution particulate matter: PM1, particles less than one micron in diameter found in soot and smog; PM2.5, particles smaller than 2.5 microns in diameter that make up fly ash from coal combust; and PM10, particles less than 10 microns in diameters found in cement dust.

To draw their conclusion, the scientists examined electronic medical records in China to identify more than 3.1 million hospitalizations for stroke — both ischemic stroke, which is caused by a blood clot, and hemorrhagic stroke, which is caused by a brain bleed.

They found that of this group, 32,140 people, or 1 percent of the total, died of stroke while hospitalized.

The risks were stronger in those people who experienced ischemic stroke than in those who experienced hemorrhagic stroke, according to the study.

The greatest risk of death occurred in people who experienced ischemic stroke and were exposed to the smallest air pollution particles, PM1, the scientists observed.

But the researchers also found that a reduction in PM10 would have the greatest overall impact in reducing deaths from stroke — decreasing the number of hospital deaths by 10 percent for short-term exposure and by 21 percent for long-term exposure.

“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.

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