For release: Wednesday, July 20, 2011
New research shows that in addition to facing a higher risk of stroke and stroke-related death, people living in a part of the Southeastern U.S. known as the Stroke Belt are also at higher risk for cognitive decline as they age.
| In the U.S., stroke mortality is about 20 percent|
higher than the national average in the Stroke Belt, and about 40 percent higher in the Belt's "buckle" (in gold).
The Stroke Belt includes Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee. Stroke mortality in the region is about 20 percent higher than the average across the U.S., and is highest among African Americans. Nationwide, African Americans aged 35-64 have three to four times the risk of dying from stroke compared to whites.
The new findings come from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study. Supported by the National Institute of Neurological Disorders and Stroke (NINDS), the study seeks to explain the heightened stroke mortality of African Americans and Stroke Belt residents – in part by examining risk factors for stroke, such as high blood pressure and diabetes.
Since 2003, the study has followed more than 30,000 people age 45 and over. About half of the participants are from the Stroke Belt and the rest are from the 40 other mainland states and Washington, D.C.
Stroke – a blockage or rupture of a blood vessel that supplies the brain – can cause a host of cognitive disabilities, including effects on memory, speech and language, and day-to-day problem solving. But even without suffering a stroke, individuals at risk for stroke may experience cognitive problems as the health of their blood vessels deteriorates.
"We think of cognitive decline as a marker for changes in the brain that increase the risk of stroke," said Virginia Wadley, Ph.D., a REGARDS investigator and an associate professor of medicine at the University of Alabama at Birmingham (UAB). Some day, she explained, measures of cognitive decline could be combined with other risk factors to help people manage their stroke risk. In the Annals of Neurology,* Dr. Wadley and her colleagues report that the incidence of cognitive decline is 18-40 percent higher in the Stroke Belt than it is outside the Belt.
The analysis involved about 24,000 participants from the REGARDS cohort. Those with a history of strokes or cognitive impairment were excluded. Each year, from December 2003 to October 2010, participants were given a six-item assessment over the phone. They were asked for the correct date (year, month and day), and asked to remember and recite a list of three items after a few minutes delay. Cognitive decline was defined as shift from a score of five or six correct items to four or fewer correct items at the last assessment.
"This is not an intelligence test or a diagnostic tool," said Dr. Wadley. "It's a screening tool to detect cognitive changes over time."
During the seven year analysis, 1,937 (8.1 percent) of participants nationwide had scores indicating cognitive decline. Six of eight Stroke Belt states had an incidence of cognitive decline higher than this national average, while about two-thirds of states outside the Belt were below the national average. The odds of cognitive decline were 18 percent higher in the Stroke Belt than in the other states.
In a more stringent analysis, the researchers focused on 438 people who scored as cognitively impaired on their last twoassessments. In this dataset, the odds of cognitive decline were 40 percent higher in the Stroke Belt.
Living inside or outside the Stroke Belt, however, was not the strongest predictor of cognitive decline. As expected, some of the most potent risk factors for stroke – including age and race – had a much stronger association. Depending on whether the researchers looked at the large dataset or the more stringent data, the odds of cognitive decline were two to three times higher for each 10-year increment in age, and for African Americans compared to European Americans. Also, compared to college graduates, people who had not finished high school were two to three times more likely to show cognitive decline.
"Persons diagnosed with stroke as well as those with asymptomatic strokes found by brain imaging have long been known to have increased risk of dementia. These data from REGARDS underline the importance of determining whether controlling stroke risk factors might prevent not only stroke but also cognitive decline," said Walter Koroshetz, M.D., deputy director of NINDS.
Since 2006, the REGARDS team has been giving participants an expanded cognitive assessment intended to provide more information about memory and thinking ability. They are also collecting data on whether people who have cognitive decline but no history of stroke eventually do have strokes. "We hope to identify domain-specific tests that are more specific for predicting the risk of stroke, as opposed to Alzheimer's disease or other neurodegenerative diseases associated with cognitive decline," Dr. Wadley said.
They also will investigate whether cognitive decline correlates with treatable risk factors for stroke. Prior data from REGARDS show that high blood pressure and diabetes are more common in the Stroke Belt.
"Our hypothesis is that these factors are playing a role in regional differences in cognitive decline," said George Howard, Dr.PH., the principal investigator for REGARDS and chair of the biostatistics department at UAB. "We want to know what is driving the higher incidence of stroke and cognitive decline in the Stroke Belt, so that we can intervene."
He said the participants in REGARDS deserve high praise, because "the things we learn from them could help everyone in the country live longer healthier lives."
- By Daniel Stimson, Ph.D.
*Wadley VG et al. "Incident cognitive impairment is elevated in the Stroke Belt: The REGARDS Study." Annals of Neurology, published online May 26, 2011.
Last Modified July 20, 2011