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updated 2/3/2011 4:08:27 PM ET 2011-02-03T21:08:27

Brain microbleeds, stemming from tiny, ruptured blood vessels, might help explain how blood vessel damage and amyloid plaque buildup work together to cause Alzheimer's disease, a new review of studies suggests.

Microbleeds, which have long been perceived as harmless and irrelevant in disease development, were found in 23 percent of patients with Alzheimer's disease in the review of five studies. A previous study showed that 6.5 percent of healthy 45- to 50-year-olds have microbleeds, whereas 35.7 percent of people 80 and older have them.

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Though that percentage is not high, it shows that blood vessel damage is occurring in some people with the disease, said study researcher Wiesje van der Flier, of Visje University Medical Centre in Amsterdam.

Many researchers agree that Alzheimer's disease is associated with both blood vessel damage and the accumulation of amyloid plaques in the brain, he said. This new review found that microbleeds could be a link between the causes.

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"We now proposed that microbleeds are an example of amyloid pathology meets vascular [blood vessel] damage," because they represent blood vessel damage that occurs simultaneously with Alzheimer's disease, van der Flier told MyHealthNewsDaily.

The study was published online Jan. 21 in the journal Brain: A Journal of Neurology.

Origins of microbleeds

Past studies have established that microbleeds are not a predictive sign of Alzheimer's disease, and their root cause is still unknown. But researchers know they are evidence of very small ruptures in the brain's blood vessels, Van der Flier said.

There are two ways microbleeds could occur. The first is that some risk factors — such as smoking, diabetes or hypertension — deprive the brain's blood vessels of oxygen, causing them to stiffen and increasing their likelihood of tearing, he said.

Microbleeds could also crop up from deposits of amyloid beta proteins — long thought to be at work in Alzheimer's — gathering in vessel walls. The protein buildup damages the vessels, spurring microbleeds, he said.

Researchers have long known that blood vessel damage is common among Alzheimer's patients. And past studies have shown that people with high blood pressure, blood vessel disorders and those who've suffered strokes are at an increased risk of Alzheimer's disease, said Maria C. Carrillo, senior director of Medical and Scientific Relations at the Alzheimer's Association, who was not involved with the study.

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There is not yet enough evidence to say that microbleeds are associated with Alzheimer's disease, but they are a sign of vascular damage that could contribute to the disease, she said.

Gateway to personalized medicine

The review shows that the cause of Alzheimer's isn't necessarily the same for everyone, Carrillo said.

"It's a perfect storm building up over time, and the contributors to that storm are different because everyone is different — including genetics, lifestyle — all those things combined," Carrillo told MyHealthNewsDaily. "They make your risk factors different from mine."

And if Alzheimer's has multiple causes, the disease might be managed more effectively taking that into consideration, rather than treating it in a one-size-fits-all way, she said.

"[A microbleed] could be a contributor in some people, and in others it's not," Carrillo said. "So we can't look at it as the only cause, but it's important to see what its role is in people who actually have one."

Pass it on: Brain microbleeds, which are small ruptures of blood vessels, could provide evidence that blood vessel damage and amyloid plaque buildup are together linked with development of Alzheimer's disease.

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