The data is from UAB's Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, which has enrolled more than 30,200 U.S. participants. The study confirms a greater-than 40 percent higher stroke death rate in eight southeastern states known as the Stroke Belt – Alabama, Arkansas, Georgia, Louisiana, Mississippi, North and South Carolina and Tennessee.
After factoring in age, race and sex-related factors, the predicted stroke risk was only slightly higher in Stoke Belt states compared to other regions (10.7 percent versus 10.1 percent), said George Howard, Dr.PH., professor of biostatistics in UAB's School of Public Health and a REGARDS principal. That risk was calculated using nine known risk factors common to stroke screening.
"We found geographic and racial differences are useful in predicting stroke risk, but they only explain less than half the picture. Something else is happening," Howard said. "It could be exposure to allergens in the home, it could be micronutrients in drinking water or it could be other factors considered 'non-traditional' because they don't fall into the list of nine factors commonly used to predict stroke risk."
The findings are reported in the Annals of Neurology.
All minority groups, including Native Americans, Hispanics and African-Americans, face a significantly higher risk for stroke and death from stroke compared to whites, and research is focused on exactly why that is, said Mary Cushman, M.D., of the University of Vermont, the study's lead author. Continued analysis of REGARDS data and follow-up study will determine other stroke risk factors and their significance.
One detail that emerged in the Annals of Neurology study is that the prevalence of diabetes and hypertension was up to five percentage points higher in the Southeast. That means interventions to reduce geographic disparities in diabetes and hypertension – including boosting diabetes screening rates and follow-up care – could also reduce geographic disparities in stroke death, Howard said.