Air Pollution Linked to Stroke

Oct. 10, 2003 -- Air pollution causes lung disease. Air pollution causes heart disease. And now, it seems, air pollution causes stroke, too.

Kaohsiung is Taiwan's second largest city. It's the heart of Taiwan's heavy industry. A four-year study of hospital admissions in Kaohsiung shows that hospital admissions for stroke skyrocket on days when the air pollution is bad.

The findings come from researchers led by Chun-Yuh Yang, PhD, MPH, director and dean of the Institute of Public Health, Kaohsiung Medical University. They appear in this week's rapid access issue of Stroke: Journal of the American Heart Association.

"Particulate matter and nitrogen dioxide seem to be the most important pollutants, and the effects appear to be stronger on warm days," Yang says in a news release.

Stroke is disease that affects the blood vessels of the brain. A stroke can occur when a blood vessel that supplies oxygen to the brain bursts or when it gets clogged with a blood clot.

Air pollution had the strongest effect on burst blood vessels in the brain. But there was also an effect on blood clots blocking blood flow to the brain.

What happens? Yang and colleagues speculate that air pollution irritates and inflame small structures deep inside the lung. This causes an increase in blood coagulation, making blood clots more likely. Pollution thickens the blood and increases the heart rate. This may cause clots to break loose and enter the circulation.

Whatever the mechanism, it's pretty clear that bad air is bad for you.

"In hot weather, we recommend that people avoid pollution, stay inside, and use an air conditioner," Yang says.