FRIDAY, Feb. 22, 2008 (HealthDay News) -- Older people whose health conditions put them at high risk for stroke are more likely to suffer from memory loss, even if they never actually have a stroke, new research shows.
The cause could be mini-strokes that people don't notice but that nonetheless contribute to the brain's deterioration. "Stroke risk factors really matter, and they matter even if you don't have a stroke," said study author George Howard, chairman of biostatistics at the University of Alabama in Birmingham.
Three risk factors in particular were linked to memory loss -- high systolic blood pressure (that's the top number in a blood-pressure reading), diabetes, and left ventricular hypertrophy (thickening of part of the heart muscle, often caused by high blood pressure).
Researchers interviewed 17,626 people who were enrolled in a national study as of last June. The average age of participants was 66, almost 40 percent were black, and none had suffered a stroke. The average systolic blood pressure in the group was 127.9, 56 percent had hypertension, 19.3 percent had diabetes, 21.9 percent had heart disease, and 6.5 percent had left ventricular hypertrophy.
While the study included people in every state but Alaska and Hawaii, its goals were to shed light on the so-called Stroke Belt, an area of the South where stroke rates are high, and to explain why blacks have such high stroke rates.
To test their mental skills, researchers gave three common words to the participants during a phone call and later asked them to repeat the words.
Then the researchers tried to find any connections between scores on the mental test and risk factors for stroke.
The findings were expected to be reported Friday at the American Stroke Association's International Stroke Conference in New Orleans.
The rate of cognitive decline in one group of participants, those with a 22 percent chance of having a stroke in the next 10 years, was double that of those who had a 2 percent chance of stroke in the next 10 years.
"What I think is happening, and what a lot of other people think is happening, is that people develop small strokes that are not significantly big enough to disable you, but cumulatively knock your [mental] condition down," Howard said.
Mini-strokes are not that uncommon, he said. Starting at age 55, about 10 percent of people who report never having had a stroke show evidence of one when they undergo brain scans, he said. The number grows to about half by age 80. Those mini-strokes create holes in the brain where blood flow has been restricted.
Dr. Argye Hillis, an associate professor of neurology at Johns Hopkins University, said the study "provides the strongest evidence of the association between the risk factors and cognitive decline."
It's not clear, though, if the risk factors directly cause brain deterioration or if they're part of a larger complex of conditions, she said. For example, people with diabetes and high blood pressure may be prone to have inflammation of the blood vessels, leading to mini-strokes, she said.
Other factors, such as a sedentary lifestyle, could also play a part, she said.
Learn more about stroke from the National Institutes of Health.