Polluted Air Might Increase Stroke Risk

High hourly rates more than double the chances of an attack, study says

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THURSDAY, Sept. 21, 2006 (HealthDay News) -- The pollution you breathe now may increase your risk of having a stroke within the next two hours, according to new research.

In an article published online ahead of print in Occupational and Environmental Medicine, researchers assessed data on stroke deaths in people ages 65 and older that occurred between January 1990 and December 1994 in 13 major urban areas in Japan.

The researchers tracked levels of air pollutants -- including nitrogen dioxide, particulate matter, and photochemical oxidants -- on an hourly basis in each of the 13 areas.

They found that between the months of April and September, the risk of hemorrhagic stroke -- when a blood vessel bursts in the brain -- more than doubled two hours after high hourly rates of particulate matter (in excess of 200 micrograms per cubic meter) were observed.

This effect was not found for ischemic stroke, when arteries in the brain become blocked. The researchers propose this may be because the time lag between the start of an ischemic stroke is longer than that for a hemorrhagic stroke.

Previous research showed that the effects of air pollution act quickly on the body, the authors said, with inhaled particles detectable in the blood within 60 seconds.

More information

The National Institute for Neurological Disorders and Stroke has more about stroke.

SOURCE: BMJ Specialty Journals, news release, Sept. 20, 2006

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