Do you live in a neighborhood with a lot of fast-food joints? Be advised: a new study suggests that living in an area densely packed with fast food ups the odds you will suffer from a stroke.

Lewis Morgenstern, who directs the University of Michigan’s stroke program in Ann Arbor, and colleagues studied ischemic strokes (caused by blocked vessels supplying blood to the brain) occurring between January 2000 and June 2003 in Southern Texas's Nueces County, which has a population of about 320,000. During that time period, 1,247 strokes occurred among people ages 45 and older.

The researchers found that the risk of suffering a stroke was 13 percent higher for people living in neighborhoods with the greatest number of fast-food restaurants (an average of 33) compared to those living in areas with the least (an average of 12), and the risk of stroke in a neighborhood increased by 1 percent for every fast-food restaurant.

"We found there was a significant association between stroke risk and the density of fast-food restaurants," says Morgenstern, who presented the results yesterday at the American Stroke Association’s International Stroke Conference in San Diego, Calif.

Morgenstern wouldn’t say which fast-food joints the study looked at, but the restaurants had to have at least two of the following four features: offering a takeout service, having limited or no waiting staff, requiring customers to pay before giving them food, or having pre-prepared food.

Morgenstern is quick to note that the study only shows an association between fast-food restaurants and stroke, not any cause-and-effect relationship. "We have no information that any of the people who have suffered a stroke [in this study] have ever eaten fast food in their whole life," he says. Perhaps easy access to fast food leads to increased consumption of the greasy goods, upping the likelihood of stroke by clogging arteries, Morgenstern speculates. Or, he hypothesizes, fast-food joints might be markers for other neighborhood risk factors, such as air pollution (previous research by Morgenstern's team linked air pollution to stroke), lack of access to parks for doing exercise (one study showed that brisk walking for even a half hour each day lowered stroke risk), or perhaps even high crime rates, which might create a stressful environment (some researchers have suggested that high stress can up stroke risk by as much as 40 percent).

"[These findings] highlight the need to look beyond the conventional risk factors for stroke [such as high blood pressure, diabetes, and tobacco use]," Morgenstern says, noting that scientists should also look at neighborhood-associated risk factors that may be at play.

The next step, Morgenstern says, is ferreting out what it is about neighborhoods with large numbers of fast-food restaurants that makes it likely residents will have strokes. He hopes to conduct a similar study comparing food consumption among those who suffer from strokes and those who do not.

A restaurant trade group slammed the study, calling it misleading. "This article is seriously flawed, and by its own admission shows no correlation whatsoever between dining at chain restaurants and incidence of stroke," says Beth Johnson, a spokesperson for the National Restaurant Association.

Behind cancer and heart disease, stroke is the third leading cause of death in the U.S. -- almost 800,000 people suffer from a new or recurrent stroke every year, 87 percent of which are ischemic, according to the American Heart Association. (The annual rate of people who had ischemic strokes in Nueces County appears to be lower than the national average—approximately 0.1 percent versus approximately 0.2 percent—but Morgenstern says his study did not compare stroke incidence in Nueces County to that of the U.S. overall.)

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