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    Dementia Seen in More Than 25% of Stroke Survivors

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    Desmond, assistant professor of pathology and neurology at SUNY Downstate Medical Center in Brooklyn, says that his study may actually have underestimated the number of patients who develop dementia after stroke. One reason is that the study used a conservative definition of dementia. Another reason is that because dementia indicates that the person suffered a more severe stroke, many patients with dementia died before they could be tested.

    The study analyzed stroke patients at a community health center in northern Manhattan. It found three types of risk factors for dementia after stroke. The first type depended on the part of the brain affected by the stroke: people who had damage to the left side of the brain, which controls language functions and abstract thinking, were more likely to suffer dementia.

    The second type depended on a person's risk factors for severe stroke: patients with diabetes or a prior stroke had increased risk of dementia. The third type of risk depended on patient factors: ethnicity, education, and old age were the major factors involved.

    Why would education be a risk? Desmond points to studies showing that education and a stimulating childhood environment increases the number of connections between brain cells. He suggests that when a stroke hits, these extra connections may help educated people compensate better.

    Stroke expert Charles P. Warlow, FRCP, professor of medical neurology at University of Edinburgh in Scotland, warns that dementia is not something that occurs overnight, even in stroke patients. In an interview with WebMD, Warlow says that a stroke may exacerbate underlying dementia as well as cause it.

    "The rate of dementia in any study depends on how you define it -- it is not something that just happens one day," he says. "Somebody can have a stroke and as a consequence of the stoke has some memory problem. Now how does that qualify as dementia? The time at which you blow the whistle and say 'Now this person has dementia' varies. There are plenty of stroke patients who are demented, and probably the stroke itself has a lot to do with it. The interesting thing is whether stroke accelerates dementia that is going on already."

    The most common cause of dementia is Alzheimer's disease (AD), and the current study finds a link to stroke: about a third of the patients who had dementia after stroke also had AD. "There is a closer link between vascular disease and AD than we have been thinking lately," says Marler. He says his agency is working to increase collaboration between stroke and AD researchers.

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