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Hypertension, Alzheimer’s Linked

High Blood Pressure Impedes Blood Flow to Brain
By
WebMD Health News
Reviewed by Louise Chang, MD

Nov. 28, 2007 (Chicago) -- High blood pressure reduces blood flow to the area of the brain that controls memory and learning, perhaps raising the risk of Alzheimer's disease, researchers report.

University of Pittsburgh researchers used a modified magnetic resonance imaging (MRI) technique to look at blood flow in the brain of 68 older adults. Forty-eight of them had no memory problems, 20 had Alzheimer's disease, and 20 had mild cognitive impairment, which is marked by memory problems that aren't severe enough for dementia diagnosis.

At least half of the people in all three groups had high blood pressure.

They found that blood flow to the hippocampus -- the seahorse-shaped structure in the middle of the brain that controls memory and learning -- was significantly reduced in people with high blood pressure, whether they had memory problems or not.

"If high blood pressure reduces blood flow to an area of the brain known to be affected in Alzheimer's disease, it makes you wonder if it's a risk factor, although this still has to be tested," says Cyrus Raji, an MD, PhD candidate at the University of Pittsburgh who presented the findings here at the annual meeting of the Radiological Society of North America.

"If true, then it's even more important to prevent and aggressively treat high blood pressure," Raji tells WebMD.

Scans Safe for Elderly

All the study participants underwent arterial spin-labeled MRI, a noninvasive technique.

The scans showed that in people with Alzheimer's, blood flow to every part of the brain studied was substantially lower in those with hypertension, compared with those who didn't have high blood pressure.

Interestingly, the link between hypertension and impeded blood flow to both the hippocampus and other parts of the brain held true even though many of the participants were taking medication to lower their blood pressure, Raji says.

The reason, he says, is that treated or not, high blood pressure makes your blood vessels narrower and less pliable over time.

Narrower, less pliable blood vessels hinder delivery of nutrients in the blood to the brain, says Philip O. Alderson, MD, of Columbia University in New York and moderator of a news conference to discuss the findings.

"Since Alzheimer's disease is marked by abnormal metabolism in an area of the brain associated with memory, you could imagine that poor delivery of nutrients to that part of the brain would make you more susceptible to the symptoms of Alzheimer's disease," he tells WebMD.

According to the National Heart, Lung and Blood Institute, about 50 million Americans have hypertension.

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