Stroke victims more likely to develop Alzheimer's

By John Fauber
Milwaukee Journal Sentinel

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MILWAUKEE — One of the best ways to avoid getting Alzheimer's disease may be to ward off another devastating neurological disorder: stroke.

Research being published today found that people who had suffered a stroke were about 60 percent more likely to develop Alzheimer's disease than those who had never had a stroke.

The research links the two most disabling brain disorders and suggests that measures taken to prevent one may also help prevent the other.

For years, doctors have known that people with poor vascular health were at higher risk for developing a stroke. And people who have had strokes are at greater risk for developing vascular dementia, a disease that is similar to Alzheimer's but that is caused by a different mechanism.

Both vascular dementia and Alzheimer's disease involve the progressive loss of memory and impairment of cognitive function.

Vascular dementia, which is the second-most-common dementia after Alzheimer's, has several forms, but all involve a lack of blood supply to the brain.

Alzheimer's, on the other hand, develops after clumps of malformed proteins form around and inside brain cells.

Over the years, doctors have changed their thinking about dementia.

"There was a time 30 or 40 years ago when almost everyone with dementia was thought to have vascular dementia," said study co-author Lawrence Honig, an associate professor of clinical neurology at Columbia University Medical Center.

Doctors since have come to realize that the leading cause of dementia is Alzheimer's, which now affects 4.5 million Americans and is expected to increase dramatically in the next two decades as the population ages. It is found in 10 percent of all people over the age of 65 and half of those over 85.

The study, which appears in the Archives of Neurology, offers two explanations of how stroke and Alzheimer's are linked.

One theory is that poor vascular health in the brain may accelerate the symptoms of Alzheimer's. Honig used the analogy of a car engine that is not working well but still is getting along. Suddenly, it gets a tank of bad gas, causing it to sputter and die.

However, the Columbia study also supports the possibility there may be a common underlying physiological cause that makes some people more prone to both stroke and Alzheimer's.

That's a theory now being studied by Robert Dempsey and other researchers at the University of Wisconsin-Madison.

In October, Dempsey presented findings from a small study of stroke-prone patients. Looking at the genetic makeup of the plaque in their carotid arteries, Dempsey found two proteins that are precursors to amyloid-beta, the protein that builds up in clumps in the brains of people with Alzheimer's.

The finding, which still needs to be confirmed with a larger group of patients, suggests that stroke and Alzheimer's may have a common cause.

"A deficiency in processing these proteins may be the basis for both Alzheimer's and symptomatic stroke," said, Dempsey, professor and chairman of the department of neurological surgery at the University of Wisconsin.

He added, "It (the Columbia study) is very helpful. It confirms the importance of treating the whole patient."

And while there are no proven ways to prevent Alzheimer's, there are measures that can substantially reduce the risk of stroke. They include controlling cholesterol and blood pressure and treating or preventing diabetes.

In fact, the Columbia study, which followed a diverse group of 1,776 patients for seven years, found that those who had suffered a stroke and who had heart disease were two times more likely to develop Alzheimer's.

Those who had a stroke and also had high blood pressure were 2.3 times more likely to develop Alzheimer's and those who had a stroke and also had diabetes were 4.6 times more likely to develop Alzheimer's.

"Having good heart health is good for your brain health," said co-author Richard Mayeux, a professor of neurology, psychiatry and epidemiology at Columbia.

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