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HEART Insight:
doi: 10.1097/01.HEARTI.0000398190.97441.bc
Features: Related Risk

The “Other” Dementia

Lewis, Darcy

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Cardiovascular Risk Factors Play A Role In Various Types Of Dementia, Including Alzheimer's

When people think of dementia, what first comes to mind is often Alzheimer's disease. But “dementia” is actually an umbrella term for any serious, progressive decline in a person's cognition (the process of thought) to the point that he or she can no longer perform activities of daily living without help.

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The Alzheimer's Association defines dementia in addition to memory loss, as a decline in cognitive abilities severe enough to interfere with at least one of the following skills:

▪ To speak coherently or understand language;

▪ To recognize or identify objects;

▪ To perform motor activities; and

▪ To think abstractly, make sound judgments and plan and carry out complex tasks.

With Alzheimer's, cognitive impairment is caused by damage to nerve cells in the brain; with vascular dementia — some prefer to call it “vascular cognitive impairment” — it's caused by impaired blood vessels in the brain, depriving cells of the blood and oxygen that they need to maintain cognitive health.

According to the National Center for Health Statistics (NCHS), Alzheimer's accounts for 50 to 70 percent of dementias. And 5.1 million Americans over 65 — or one in eight — have Alzheimer's disease. While vascular dementia is believed to be the second most common form of dementia, reliable estimates of the number of Americans who have the condition are hard to come by. The Mayo Clinic estimates that one to four percent of people over the age of 65 in the U.S. have vascular dementia, but some experts believe the actual number is much higher.

Gustavo Roman, M.D., director of the Nantz National Alzheimer Center at Methodist Neurological Institute in Houston, did a meta-analysis of dementia studies in 2002 and concluded that vascular dementia “may be the most underdiagnosed and undertreated form of dementia in the elderly.” Nearly a decade later, many of his colleagues have come to share this view.

“Vascular disease in the brain is much more common than believed and interacts with Alzheimer's in ways we're just starting to understand,” says neurologist Vladimir Hachinski, M.D., Distinguished Professor at the University of Western Ontario's University Hospital in London, Ont.

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Complicating matters, the incidence of Alzheimer's and vascular dementia overlap. The Alzheimer's Association believes that up to 45 percent of people with dementia show signs of both Alzheimer's and vascular disease, a condition known as “mixed dementia.”

There appears to be a complex relationship between vascular dementia and Alzheimer's in which either disease can contribute to the other, and people who have both dementias may have worse outcomes.

“As we've moved into advanced [tools to scan] the brain, we've come to realize that cerebrovascular disease may play a major role in Alzheimer's, too,” says Philip Gorelick, M.D., director of the Center for Stroke Research at the University of Illinois College of Medicine in Chicago. “And if it occurs when you already have Alzheimer's-related changes in your brain, even without symptoms, you are much more likely to become impaired.”

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Here's what else we now know: Any condition that reduces or blocks blood flow in the brain can start the cycle of cognitive decline. “In vascular dementia, there are irreversible damages in the brain caused by vascular disease, including the blockage, rupture or leaking of blood vessels,” says Yousef Mohammad, M.D., associate professor of neurology and director of the Stroke Fellowship Program at Rush University Medical Center in Chicago. “Multiple strokes are the major cause of vascular dementia.”

But a single stroke that deprives a significant portion of the brain of its blood supply can lead to vascular dementia. “Around one-third of stroke survivors age 65 and above develop vascular dementia within three months,” notes Roman, lead author of the so-called Roman Criteria that doctors may use to diagnose vascular dementia. “One of the first questions I always ask new patients is whether there has been a stroke within the recent past,” he adds.

In many people with vascular dementia, the actual damage to the small blood vessels in the brain occurs gradually due to a series of small or even undetectable strokes, known as “silent strokes” or transient ischemic attacks (TIA). “For each stroke we see, we believe there are at least five silent strokes that don't get diagnosed because they don't affect the body in obvious ways,” says Hachinski. “The person is often totally unaware he has had a stroke. But once the harmful changes inside the brain reach a tipping point, the person typically declines quickly.”

But strokes and TIAs are not the only suspected culprits in vascular cognitive decline. Others include, atherosclerosis (or hardening) of arteries in the brain, and cerebral amyloid angiopathy, which is the build-up of amyloid protein in the brain's blood vessels. “When amyloid accumulates in the blood vessels, it tends to make them ‘leaky’, which produces small strokes,” notes Hachinski.

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One reason vascular cognitive decline can be challenging to diagnose is that symptoms may vary depending on which part of the brain has been affected.

“Alzheimer's is a memory disorder, but the silent strokes that cause so many cases of vascular cognitive impairment don't typically cause memory damage as their main outcome,” says Hachinski. “They typically affect the areas of the brain that control executive functions like decision-making skills and impulse control.”

Roman likens “executive dysfunction” to an airport losing its air traffic controller. “How do you complete a task? How do you do things in a safe and appropriate way?” he asks. “You can manage memory loss to a certain extent by using pencil and paper or your iPhone to stay organized. If you lose your executive capacities, that is much harder to compensate for.”

Imagine you are playing cards when the phone rings. You instantly stop thinking about your cards and how to hold them, put them down, stand up, push back your chair, locate the phone even if it is out of sight, walk to it without tripping over the dog, answer the call and have your conversation. When you finish the call, you reverse these steps and resume your card game. And you do it all without a second thought.

For a patient with vascular cognitive impairment, however, this seemingly intuitive process can get derailed at any step along the way. “It's very difficult for these patients to shift from one mode of thinking or task to another and then back again,” says Gorelick.

Executive function skills tend to determine how ably people interact with the world and with others, so any decline in these areas can bring distress to people with vascular dementia and — especially — their families. “Vascular dementia brings a progressive loss of social skills and empathy,” says Mohammad. “Patients tend to cry or laugh at very trivial or inappropriate things. They may become angry or agitated easily. Some patients complain they lack energy and are just not themselves.”

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Unfortunately, declines caused by vascular dementia are often permanent. The Food and Drug Administration (FDA) has not approved any drugs specifically for the treatment of vascular dementia, but many of the drugs used to treat cognitive symptoms of Alzheimer's may also be somewhat helpful. “Right now TLC from family and friends is probably more effective than any drug,” says Roman.

And the same lifestyle changes that reduce risk of heart attack and stroke also reduce the risk of vascular dementia. “We already know that improving risk factors like high blood pressure, high cholesterol, obesity and an inactive lifestyle can prevent cardiovascular disease, and it appears that controlling these same risk factors can prevent cerebrovascular disease as well,” says Gorelick.

Even after a person begins to show signs of cognitive vascular decline, progression can be slowed by managing cardiovascular risk factors. “We find we can actually halt the disease's progress in some patients or occasionally even help them improve by managing the factors that caused the blood vessel disease,” says Mohammad. “These are generally patients who are younger, get diagnosed early and take good care of themselves.”

Even more important: Reducing the risk of a second stroke also prevents further cognitive and physical decline. A study presented at the 2011 American Stroke Association conference in February showed that patients with dementia were twice as likely to die after suffering a stroke as those without dementia. And they were nearly twice as likely to become disabled.

“People need to know there is a strong link between vascular cognitive impairment, cardiovascular risk factors and Alzheimer's. All three are closely related and, by controlling your risk factors, you can lessen your risk of dementia,” says Gorelick.

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FIVE QUICK FACTS: About Vascular Dementia

1. Many forms of dementia — cognitive decline severe enough to interfere with daily life — exist. Alzheimer's disease, vascular dementia and a combination of these two known as mixed dementia are the most common.

2. Vascular dementia, or blood vessel disease in the brain, is typically caused by one or more strokes or other conditions closely related to cardiovascular disease.

3. It now appears that vascular dementia and Alzheimer's can each contribute to the other. People who have both may have worse outcomes than those with only one.

4. Vascular dementia, stroke and heart disease all share common risk factors, including high blood pressure, high cholesterol, diabetes, obesity and sleep apnea. Fortunately, these are generally very controllable. Vascular dementia may be preventable with long-term control of these risk factors.

5. Treatment focuses mainly on how to slow disease progression. Some drugs may help with Alzheimer's and may reverse vascular dementia symptoms in some people but are not currently FDA-approved for this purpose.

© 2011 American Heart Association, Inc.