Cerebrovascular disease, which includes stroke, is the second leading cause of death and the major cause of long-term disability in Western societies, according to background information in the article. Several studies have shown that risk factors for vascular disease, such as diabetes and hypertension, are associated with stroke, which in turn may increase the risk for dementia and Alzheimer's disease. However, it remains unclear whether stroke is directly related to cognitive decline--increasing problems with thinking, learning and memory--in patients without dementia or cognitive impairment.

Christiane Reitz, M.D., and colleagues at Columbia University, New York, studied 1,271 elderly patients (386 men, 885 women, with an average age of 76.2 years) without dementia or cognitive impairment. Between Jan. 4, 1992, and Dec. 24, 1994, participants underwent an initial interview and evaluation and also took a series of neuropsychological tests to gauge their cognitive abilities. They were then examined at 18-month intervals through Nov. 24, 1999.

At the beginning of the study, 7.6 percent of patients had a history of stroke. All participants experienced a decline in memory over time, but the decline was more rapid in those patients with a history of stroke. The association was stronger in men and individuals without a particular type of gene known as an APOEe4 allele, which has been linked to Alzheimer's disease in previous research. Abstract/visuospatial abilities, which do not involve language, also declined among men and those without the APOEe4 allele who also had a history of stroke.

"The mechanisms by which stroke increases the risk of cognitive decline are not clear," the authors write. Stroke may increase the risk of memory problems by destroying or damaging certain areas of the brain or by triggering the deposit of materials that form the hallmark brain plaques associated with Alzheimer's disease. "It is also possible that the occurrence of stroke adds cognitive deficits in person with subclinical Alzheimer's disease that bring them over the diagnostic threshold  and that stroke does not have a direct specific effect on Alzheimer's disease."

"A history of stroke is related to a progressive decline in memory and abstract/visuospatial performance, especially among men and those without an APOEe4 allele," they conclude.

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