Air pollution increases chance of stroke, study says

Smoke is released into the sky at a refinery in Wilmington, California (Reuters / Bret Hartman)
People living in areas with high air pollution, such as New York City, face a greater risk of stroke according to a new study from New York University’s Langone Medical Center.

The study found that fine particulate matter produced from burning wood or coal or from car exhaust can contribute to a narrowing of the arteries that supply blood to the brain, or carotid artery stenosis. This constriction of the arteries is associated with more than half of the strokes that occur in the United States each year.

Our study adds to the growing body of evidence that air pollution is a significant risk factor for cardiovascular disease,” said Jonathan D. Newman, M.D., M.P.H., a cardiologist at NYU Langone Medical Center and the study's lead author. “It shows that a person's cardiovascular risk is not only associated with their genes, health behaviors and lifestyle choices, it also depends to some extent on the world we live in and the air we breathe.”

The screening of 300,000 people living in New York, New Jersey and Connecticut was a voluntary, self-pay program that studied the health of participants’ hearts and arteries using cardiovascular ultrasounds and other tests. Researchers analyzed the levels of air pollution in each person’s home ZIP code, based on air quality measurements collected by the Environmental Protection Agency from 2003-2008, and the relationship between it and carotid artery stenosis.

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They found that those living in ZIP codes in the top quartile for air pollution had a 24 percent greater risk of stroke compared to those living in the bottom quartile ZIP codes.

The results draw attention to the importance of strategies to reduce air pollution,” Newman said. “If you're in good health, the level of air pollution we see in most parts of the United States probably doesn't pose a significant health risk to you. But for people who are very young, very old or have other medical problems, air pollution could be a significant source of cardiovascular disease risk.”

The findings also point to air pollution as one potential factor that could help explain why some people, such as those with diabetes, seem to be more susceptible to cardiovascular problems than others.

“People with other cardiovascular risk factors would be wise to limit the amount of time spent outdoors on days when air pollution levels are high,” Newman said.

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Newman said future studies could broaden research to include 3.5 million people nationwide using the same measurements.

The study, “Particulate Air Pollution and Carotid Artery Stenosis,” will be presented at the American College of Cardiology’s 64th Annual Scientific Session in San Diego on March 16.

Previous studies have linked air pollution with cardiovascular problems, but they focused on the heart and its surrounding arteries rather than the neck and head.