Air pollution may increase risk of stroke

Air pollution has been linked to a dangerous narrowing of neck arteries that may raise your risk for stroke, U.S. researchers said Monday.

The researchers analyzed medical test records for more than 300, 000 people living in New York, New Jersey or Connecticut.

They found that people living in regions with the highest average levels of air pollution were 24 percent more likely to show signs of narrowing in their internal carotid arteries, compared to those living in regions with the lowest pollution levels.

The research focused on fine particulate matter pollutants, also called "PM 2.5 pollutants," which are particulates with diameters less than 2.5 micrometers. PM 2.5 is the most common form of air pollution and stems largely from combustion-related sources, such as car exhaust and the burning of coal or wood.

"We spend a lot of time thinking about traditional risk factors for stroke such as high blood pressure, cholesterol, diabetes and smoking -- but our data underscore the possibility that everyday air pollution may also pose a significant stroke risk," said senior investigator Jeffrey Berger, assistant professor in New York University Langone Medical Center, in a statement.

The two internal carotid arteries are situated on either side of the neck and provide most of the brain's blood supply. Strokes often result when accumulated plaque breaks off from a narrowed section of an internal carotid artery and blocks smaller vessels in the brain.

Scientists aren't yet sure how air pollution contributes to vascular diseases such as stroke. Studies have indicated that it may do so in part by causing adverse chemical changes to cholesterol in the blood, by promoting inflammation, and by making blood platelets more likely to form clots.

The findings were presented at the American College of Cardiology's 64th Annual Scientific Session in San Diego and published online in the Journal of the American College of Cardiology.