December 15, 2003
Men and women who have had a stroke are at increased risk of developing Alzheimer's, especially if they also have heart disease. Those are the findings of a large and rigorous new study that appeared in this months issues of the Archives of Neurology, a medical journal for physicians.
Researchers from Columbia University's College of Physicians & Surgeons in New York City followed 1,766 elderly Medicare recipients living in upper Manhattan from 1992 to 1999. All were free of symptoms of Alzheimer's at the start of the study. Some had suffered from earlier strokes; others had not. They ranged in age from 65 to 105, with a mean age of 77 years.
Each year of the study, more than 5 percent of the seniors who had had an earlier stroke developed symptoms of Alzheimer's disease, while only 4 percent of those with no stroke history did. That means that stroke patients were roughly 60 percent more likely to develop Alzheimer's than those who had never had a stroke, The risk of dementia was greatest in those stroke patients who also suffered from high blood pressure, heart disease, or diabetes.
"Compared with persons with no history of stroke, there was an increased risk of Alzheimer's disease in persons with a history of stroke," the authors write. "Moreover, a history of stroke was associated with an earlier age at onset of dementia."
Both strokes and Alzheimer's are common in older people. The relation between the two conditions, however, remains unclear.
In a stroke, sometimes called a "brain attack" because the disease process resembles what happens during a heart attack, the oxygen supply to the brain is cut off because of blocked or leaking blood vessels. As a result, healthy brain cells become damaged. In addition to partial paralysis, slurred speech, and other physical impairments, stroke may blunt thinking or memory skills. Unlike the progressive mental decline of Alzheimer's, however, people affected by stroke may gradually recover some or all of these skills.
Some research suggests that strokes, even small ones that are barely perceptible, may damage the brain and predispose to the onset of dementia. In autopsies of people with Alzheimer's who have died, for example, those who have evidence of stroke damage to the brain tend to have more severe symptoms of mental decline. It is possible that some of the same vascular, or blood vessel, problems that lead to strokes and heart disease could also play a role in the onset of Alzheimer's.
Alternatively, strokes may just be another brain ailment of the elderly that co-exists along with Alzheimer's. Strokes may damage healthy nerve cells and reduce brain power, causing memory loss and other symptoms of dementia to appear earlier in the course of Alzheimer's.
"Neurologists have long diagnosed dementia as a dichotomy, with pure vascular origin on one hand and pure degenerative origin on the other," comments Dr. Samuel Gandy, Chairman of the Scientific Advisory Board of the Fisher Center for Alzheimer's Research Foundation. "Neuropathologists, however, have frequently noted coexistent pathology when brains are examined at autopsy. As always, the pathologists have the final say. It is becoming apparent that a continuum may exist for Alzheimer's, in which many patients have coexistent diseases because, as this study shows, stroke increases the risk for Alzheimer's." Regardless of the exact relationship between blood vessel disease and Alzheimer's, the authors of the current study conclude that prevention of stroke and heart disease remains an important goal. Among the measures experts recommend:
*If you're overweight, drop some pounds.
*If you smoke, quit.
*Get regular medical checkups. If you develop high blood pressure or high cholesterol, get treated for it.
*If you drink alcohol, limit yourself to one to two drinks a day.
*Exercise regularly. Check with your physician about a routine that's right for you.
*Eat a diet rich in fruits and vegetables and low in artery-clogging fats.
*Ask your doctor if "an aspirin a day" is right for you. Aspirin and other drugs can limit your chance of having a stroke.
For more on the causes of and risk factors for Alzheimer's disease, visit the alzinfo.org research discussion at:
By www.ALZinfo.org, The Alzheimer's Information Site. Reviewed by Samuel E. Gandy, M.D., Ph.D., Chairman of the Scientific Advisory Board, Fisher Center for Alzheimer's Research Foundation.