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Researchers may have found a new risk factor for Alzheimer's disease. The culprit? Leaky blood vessels in the brain. NPR's Jon Hamilton reports that the finding could eventually help doctors predict and prevent Alzheimer's and other forms of dementia.
JON HAMILTON, BYLINE: Blood vessels in the brain include a special protective layer called the blood-brain barrier. It keeps the bacteria and toxins that circulate in blood from leaking into the brain. A few years ago, some researchers noticed that this barrier is damaged in people who die of Alzheimer's. Berislav Zlokovic is at the University of Southern California.
BERISLAV ZLOKOVIC: We're looking at brains from autopsies, and it becomes quite apparent that there is breakdown of the blood-brain barrier.
HAMILTON: But wasn't clear whether the breakdown was happening before Alzheimer's appeared or after. In other words, was it a potential cause or just byproduct of the disease? To find out, Zlokovic used a special type of MRI to study the brains of more than 60 people. These included both healthy individuals and people with mild cognitive impairment, which can be an early sign of Alzheimer's. Zlokovic says he paid special attention to the hippocampus, one of the first brain areas affected by Alzheimer's.
ZLOKOVIC: There is an increase in the blood-brain barrier breakdown by about 40 to 50 percent in the hippocampus, the brain region that is involved with memory and learning.
HAMILTON: Blood vessels are much leakier in people with cognitive problems. And Zlokovic believes that is exposing their brains to toxic substances.
ZLOKOVIC: Leading to loss of brain cells eventually or loss of connections between different brain cells.
HAMILTON: The hallmarks of Alzheimer's disease. The finding could help explain why people with atherosclerosis and other problems with their blood vessels are more likely to develop Alzheimer's. Rod Corriveau is a program director at the National Institute of Neurological Disorders and Stroke, which helped fund the research.
ROD CORRIVEAU: There's every reason to think a lot of Alzheimer's disease does involve vascular damage.
HAMILTON: Corriveau says the study also adds to the evidence that amyloid plaques and tangles known as tau aren't the only factors that can lead to problems with memory and thinking. He says there are probably several paths.
CORRIVEAU: One of them could be through amyloid. One of them could be through tau. One of them could be through vascular contributions. And in fact, what is more likely is that they are interactions between these and other factors to create dementia, including Alzheimer's disease.
HAMILTON: Corriveau says changes in the blood-brain barrier happen long before mental problems appear so it may be possible to use those changes as markers to predict who will go on to develop Alzheimer's disease. And Corriveau says the disease might be delayed or prevented by drugs that make blood vessels less leaky.
CORRIVEAU: This study gives patients and families hope for the future, hope that detecting leaky blood vessels early will provide the opportunity to stop dementia before it starts.
HAMILTON: The new research appears in the journal Neuron. Jon Hamilton, NPR News.
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