"This work is important because people don't just suddenly develop vascular dementia or AD--it is very likely a long-term and subtle process," Dr. Elias stated. "What our study shows is that in people who have never had a stroke or been diagnosed with dementia, there is a higher risk for performing in the lower range of cognitive ability for those who are at higher risk of stroke within 10 years. Our research shows that it is very important to consider risk factors for a future stroke as risk factors for cognitive deficits." Dr. Elias spoke today at an American Medical Association media briefing on Alzheimer's disease in New York City.
"This study shows that people who are at higher risk for stroke are at risk for lowered cognitive function and show a pattern of deficits similar to that seen in mild vascular cognitive impairment," Dr. Elias said. We hypothesize that the link between risk for future stroke and lowered cognitive performance may be due to structural and functional changes in the brain that do not rise to the level of clinical detection. Very recent evidence from a brain imaging study with a large subset of Framingham Offspring who also participated in our study indicated that abnormal brain atrophy is related both to higher risk of stroke and poorer cognitive ability."
"Mild cognitive impairment related to high risk for stroke is of concern to those who study AD for several reasons. Vascular changes related to stroke are often seen in AD and even silent strokes may play a role in precipitating AD and/or facilitating its progress."
"Lowered cognitive functioning and high risk for future stroke are early warning signs," Dr. Elias stated. "It is critically important to prevent risk factors which increase risk for stroke and to intervene early in the process of cognitive decline where the benefits of intervention are greatest and most likely to be successful."
The individuals included in the study were a community-based sample of 1,011 men and 1,164 women from the Framingham Offspring Study who participated in cognitive testing as part of the ongoing, 50-year-old Framingham Heart Study, supported by the National Heart, Lung, and Blood Institute (NHLBI) and the National Institute on Aging. The researchers used the Framingham Stroke Risk Profile (FSRP) to determine the 10-year risk of stroke and related it to the level of cognitive functioning. The FSRP computes the probability of experiencing stroke within 10 years using weighted combinations of age, systolic blood-pressure, presence of diabetes, cigarette smoking, history of cardiovascular disease, treatment for hypertension and atrial fibrillation.
After determining the risk of stroke for each individual, the researchers assessed cognitive ability by testing visual-spatial memory, concentration, attention, scanning, planning and organization (executive functioning), verbal abstract reasoning and various components of verbal learning and memory.
The study by Dr. Elias and colleagues confirmed findings, in the Framingham studies, and in other studies, that individual stroke risk factors are related to cognitive deficits and have a cumulative effect on level of performance. The uniqueness of their study is that they examined stroke risk in relation to multiple measures of cognitive functioning and did so for a large community-based sample of men and women.
Because vascular changes in the brain have been linked to cognitive performance, the study researchers hypothesize that cerebrovascular brain injury, premature shrinkage of the brain, blockage of arteries, and cerebral infarction (dead brain tissue resulting from insufficient blood to an area) may also be linked to the risk of stroke and cognitive functioning. "Interestingly a number of strong risk factors for stroke and for AD are the same," Dr. Elias stated.
An estimated 4.5 million Americans have AD and by the year 2050 it is estimated that between 11 million and 16 million will join their ranks. Currently, one in 10 people over the age of 65 has AD, and nearly half of those over 85 have it. The cost of AD in the United States alone is $100 billion annually.
"We hope our findings will stimulate further study of the association between risk for stroke and cognitive deficits in people who are currently stroke and dementia free," Dr. Elias concluded. "The findings also highlight the potential role of neuropsychological evaluation in combination with medical diagnostic techniques in the prevention and management of stroke in preserving cognitive functioning in at-risk patients."