March 11, 2008
Older Americans at high risk of stroke also have a high rate of memory loss and mental decline, even if they have never actually suffered a stroke. Those are the findings of a new report presented at the American Stroke Association's 2008 International Stroke Conference in New Orleans. The findings underline the importance of maintaining cardiovascular health to help protect the brain and memory.
"Everyone knows that people lose some cognitive function as they age," said study leader George Howard, Dr.P.H., of the University of Alabama at Birmingham School of Public Health. "We found that people at high risk of stroke decline twice as fast as those persons considered at low-risk."
High blood pressure is the greatest risk factor for stroke. Advancing age, smoking, alcohol abuse, high cholesterol, a high-fat diet, obesity, lack of exercise, heart disease and diabetes are also important risk factors for stroke.
In the study, researchers looked at more than 17,000 older men and women and assessed their stroke risks. Their average age was 65, and 38 percent were African-American. Researchers also gave them a simple cognitive test to measure memory and other brain functions. They found that stroke risk tracked closely with the annual loss of cognitive function.
"The higher your stroke risk score, the more the cognitive decline," said Dr. Howard, professor and chair of biostatistics at the University of Alabama. "This is important because it shows that if you have these stroke risk factors, even if you don't have a stroke, they are bad for you."
The researchers found that the higher your risk of having a stroke in the next 10 years, the greater the acceleration in rate of memory loss and mental decline.
The Stroke Belt
The research is part of the REGARDS, for Reasons for Geographic and Racial Differences in Stroke, study, a long-term research project involving some 30,000 African-American and white Americans ages 45 and older living in 48 states. Its main goal is to understand the high stroke death rate in the Southern United States -- sometimes called the Stroke Belt --- and among black Americans. The project uses telephone surveys to assess health status, including whether participants have suffered a heart attack or stroke, as well as annual assessments of memory and thinking skills.
Of the more than 17,000 men and women in the current study, more than half had high blood pressure, putting them at high risk for stroke. Nearly 20 percent had diabetes; more than 25 percent suffered from heart disease or had thickening of the heart wall, a sign of a failing heart; and about 13 percent smoked.
The cognitive assessment used in this study consisted of six questions, including giving study members three common words and asking them later in the telephone call to repeat them.
"A lot of people couldn't remember the words," Dr. Howard said. "If you extrapolate these effects, our findings suggest that would be an average 8 percent larger increase in missed questions after 10 years in the high-risk group," he added. "That's a large difference."
The researchers also identified three specific risk factors significantly associated with memory loss. First was high systolic blood pressure, the top number in the blood pressure ratio; a number of 120/80 is usually considered normal, so numbers above 120 would mean you were at high risk. Second was diabetes. And the third was thickening of the left heart wall, a condition known medically as "left ventricular hypertrophy."
Identifying the three conditions could have important implications for slowing the age-related decline in mental functioning. "Physicians and patients should be as vigilant as possible in controlling hypertension and diabetes because it may slow cognitive decline," Dr. Howard said.
The Fisher Center for Alzheimer's Research Foundation continues to fund critical research into the risk factors and causes of cognitive decline and Alzheimer's disease. To learn more, visit www.ALZinfo.org, The Alzheimer's Information Site.
American Stroke Association, 2008 International Stroke Conference.