Visiting the South's 'stroke buckle' increases risk of stroke death

June 5, 2008

GAINESVILLE, Fla. — It might not only be the state of your health but also the state you visit that increases the chances of dying from a stroke, a new University of Florida study finds.

Simply traveling to a region in the coastal Southeast raises the odds of a visitor succumbing to a stroke, while residents who leave the area reduce their chances of suffering the same fate, said Ilan Shrira, a University of Florida psychologist. His study is published in the current issue of the journal Neuroepidemiology.

“For decades the coastal plains of North Carolina, South Carolina and Georgia have had a high incidence of stroke deaths compared to the rest of the country,” he said. “Our research shows for the first time that even short-term exposure to this ‘stroke buckle’ is associated with higher-than-expected mortality rates.”

The “stroke buckle” is so named because it is located within the larger and more commonly known “stroke belt,” eight states in the southeastern United States that have a stroke death rate nearly one and a half times that of the rest of the country, Shrira said. The smaller buckle region has an even higher concentration of stroke deaths, he said.

Using all U.S. death certificates from 1979 to 1988, the researchers examined deaths inside and outside the stroke buckle, which comprises 153 counties in the eastern halves of Georgia, North Carolina and South Carolina. They also distinguished residents and nonresidents of the region.

They found that visitors to the region were 11 percent more likely to die of a stroke than were visitors to any other part of the U.S. Additionally, stroke buckle residents who temporarily left the area reduced their chances of stroke death by 10 percent.

Among the many explanations proposed for the existence of the stroke belt and stroke buckle are poorer health care, infectious agents, genetic predispositions and environmental toxins in the water or soil, Shrira said.
But, according to Shrira, none of the explanations has been able to account for the excess deaths, leaving the cause a mystery.

Identifying the cause has been challenging because some of the explanations are difficult to test, and the ones that are testable have not produced any convincing answers, he said.

Nor do the results resolve why short-term exposure to the ‘stroke buckle’ is related to stroke death, he said.

“The fact that it also affects visitors suggests that the effects are partially due to some factor inherent to the region itself, rather than the region’s residents,” Shrira said. “For instance, because the stroke buckle is situated in the coastal plain, and the land to the west is mountainous, the region’s distinct geography may play a role.”

Or the high death rate may be the result of some undetermined infectious agents in the region that lead to strokes, Shrira said. A number of studies have found that up to one third of all stroke victims have some kind of infection prior to the onset of an attack, he said.

“Most investigations into disease and death look at individual-level factors such as genes, diet, exercise and the like,” Shrira said. “But research like this has shown that it is not just who you are and what you do, but also where you live and where you travel to that can influence how you die.”

Shrira collaborated on the research with Nicholas Christenfeld, a psychologist at the University of California at San Diego, and George Howard, a biostatistician at the University of Alabama School of Public Health. Howard is the lead investigator of the Reasons for Geographic and Racial Differences in Stroke project, the country’s largest study investigating regional differences in stroke affliction.