What is dementia?
Dementia is the loss of mental functions—such as thinking, memory, and reasoning—that is severe enough to interfere with a person’s daily functioning. Dementia develops when the parts of the brain that are involved with learning, memory, decision-making, and language are affected by any of various infections or diseases.
What is stroke?
A stroke is damage to part of the brain tissue that results from a loss of blood and oxygen. An ischemic stroke, called an "infarct," is one
type of stroke that occurs when a blood vessel in the brain develops a clot and cuts off the blood supply to the brain.
What is the association between cerebrovascular disease and dementia?
Until the 1960s, it was thought that cerebral atherosclerosis, or "hardening of the arteries," caused dementia in the elderly. As a result, vasodilators (medications that dilate blood vessels) were used to treat "senile" dementia. However, while both atherosclerosis and dementia increase with advancing age, this does
not necessarily imply a cause and effect.
A 1970 article, "Observations on the brains of demented old people" (Tomlinson BE, Blessed G, Roth MJ. Neurol Sci 1970 Sep;11(3):205-42), published results of a study that examined the brains of 50 subjects, ages 56 to 92 (29 of the subjects were under age 75).
According to the study results:
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50% showed changes of Alzheimer’s disease
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18% showed multiple strokes (large and small)
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18% showed mixed Alzheimer’s changes and stroke
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14% showed other types of pathology
In the 1970s, the concept of "multi-infarct dementia" (MID) was introduced. MID, a common cause of dementia in the elderly, is caused by numerous small strokes in the brain. Later, in the 1980s and ’90s, this concept was broadened to "vascular dementia," which includes causes other than multiple strokes. The development of CT/MRI scans facilitated the recognition of these disorders.
The problem with the current definitions of dementia is that they are based on the "Alzheimer’s disease" model of predominant memory loss plus additional impairment. In fact, many patients with strokes have deficits in cognitive functioning that relatively spare memory, but still interfere with daily activity.
What are the risk factors for stroke and dementia?
Risk factors for stroke and dementia include:
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Age
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Hypertension. Widely acknowledged as the leading risk factor for stroke, studies show that hypertension appears to increase the risk of dementia as well.
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Diabetes. Overall, the risk of stroke is two and a half times higher in men and women with diabetes compared to people without diabetes.
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Apolipoprotein E,
4 allele. The
4 allele is one version of the apolipoprotein E gene. Presence of the4 gene may increase the risk of dementia after a stroke. It also increases the risk of late-onset Alzheimer’s and decreases its onset age.
Do "silent" strokes increase the risk of dementia?
"Silent" strokes--small blockages in arteries that supplying blood to the brain in older adults without causing symptoms--have been shown to impair cognitive function. A study by Vermeer et al reported in the
New England Journal of Medicine (Silent brain infarcts and the risk of dementia and cognitive decline. N Engl J Med 2003;348:1215-1222) concluded that older adults who experienced "silent" strokes had an
increased risk of dementia and a greater decline in cognitive
function than those who did not experience them.
© Copyright 1995-2008 The Cleveland Clinic Foundation. All rights reserved
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition.This document was last reviewed on: 3/23/2007
