THURSDAY, May 26 (HealthDay News) -- People living in an area of the southeastern United States known as the "Stroke Belt" are also at greater risk for cognitive decline, or reduced brain function, than those living in other areas, new research suggests.

The Stroke Belt states -- known to have significantly higher rates of stroke deaths than the rest of the country -- include Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee. According to the researchers, shared risk factors for stroke and brain impairment appear to be to blame for the greater incidence of cognitive decline in this geographic region.

The new study, published online May 26 in Annals of Neurology, followed more than 30,000 Americans aged 45 or older for a period of four years to document signs of stroke as well as cognitive decline.

In assessing reduced cognitive function, the researchers included nearly 24,000 participants (38 percent were black, and 62 percent were white) with normal brain function and no history of stroke. More than half of those participating in the study, or 56 percent, were from Stroke Belt states, while 44 percent were from other parts of the country.

After subjecting participants to brain function tests, including memory and perception of time, the researchers found that roughly 8 percent showed cognitive impairment over the course of the study period. In addition, those living in the Stroke Belt states had an 18 percent higher risk of cognitive decline than those living elsewhere in the country.

"Our study is the first to document higher incidence of cognitive impairment in the Stroke Belt compared to remaining U.S. regions," Virginia Wadley, associate professor of medicine at the University of Alabama at Birmingham, said in a journal news release.

One expert called the finding "extremely interesting."

"It has been known for some time that the "stroke belt" is a geographical region with a significantly higher incidence of stroke," said Dr. Richard B. Libman, chief of the division of vascular neurology at Long Island Jewish Medical Center in New Hyde Park, N.Y. "Stroke by itself is a major contributor to cognitive impairment and dementia."

The study's authors also noted that more research is needed to examine other possible risk factors for reduced brain function, including migration patterns, urban vs. rural living, socioeconomic status and education.

"Risk factors for stroke, such as high blood pressure, diabetes, etc..., are in themselves independent risk factors for cognitive impairment," Libman added. "The important message is that careful analysis of what makes the stroke belt different from other areas of the country can lead to more insight into what is causing the cognitive impairment, and, hopefully, result in effective preventive measures and treatment."

More information

The American Stroke Association provides more information on the risk factors for stroke.