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Researchers stressed that they do not know whether the brain finding can translate into any benefits for patients. But future studies should look into that possibility, they said.
The findings, published June 17 in the journal Hypertension, come from a trial of 44 patients with mild to moderate Alzheimer's. They were randomly assigned to take either the blood pressure drug nilvadipine or inactive placebo pills for six months.
In the end, patients on the drug showed a 20% increase in blood flow to the hippocampus -- a brain structure involved in memory and learning that is one of the first areas damaged by Alzheimer's.
Experts said the study was too small and short-term to know whether the improved blood flow could have any effect on symptoms.
But future research should try to answer that question and should focus on people with early Alzheimer's, said Dr. Jurgen Claassen, the study's lead author.
The research is part of a larger trial that looked at whether nilvadipine could improve Alzheimer's patients' memory and thinking skills. Overall, there was no evidence the drug helped.
But, Claassen explained, patients with early-stage Alzheimer's did show signs of a benefit.
"So a new trial should focus on those patients, and follow them longer -- at least two to three years," said Claassen, an associate professor at Radboud University Medical Center in the Netherlands.
The findings add to a body of evidence on the heart-brain connection, according to Rebecca Edelmayer, director of scientific engagement for the Alzheimer's Association.
Research has shown that some of the same risk factors for heart disease -- including high blood pressure, diabetes and obesity -- are also risk factors for dementia. Last year, Edelmayer noted, a major trial found that tight control of high blood pressure cut older adults' risk of developing mild cognitive impairment -- a precursor to dementia.
But little is known about the effects of blood pressure control in people who already have Alzheimer's. And that's why the new findings need to be followed up, Edelmayer said.
"We don't know if [blood pressure control] may be more of a preventative measure, or if it might have a role in treatment, too," she said.
Why would blood pressure matter in Alzheimer's? According to Claassen, if high blood pressure damages blood vessels supplying the brain, that might increase dysfunction in the cells there.
Brain cells need a large amount of oxygen and sugar to function well, Claassen explained. So about 15% to 20% of the body's blood flow goes to the brain, he noted.
In theory, Claassen said, better circulation to the hippocampus might allow its cells to function better -- even in people with early Alzheimer's. But this trial does not prove that.
The study -- funded by government and foundation grants -- included 44 Alzheimer's patients who were about 73 years old, on average. Half were randomly assigned to take nilvadipine for six months, while the other half received placebo pills.
Not surprisingly, patients on the real drug saw their blood pressure drop by about 11 points, compared to the placebo group.
Meanwhile, specialized MRI scans showed that blood flow to the hippocampus rose by 20%, on average, in the nilvadipine group. It remained stable in other areas of the brain.
For now, Claassen said, the findings suggest that treating high blood pressure in Alzheimer's patients is not only safe, but may even increase the brain's blood supply.
But is that an effect of the medication, or of better blood pressure control in general? It's not clear from this trial, Claassen said.
To Edelmayer, the central message is that people "have tools available today" to help preserve their brain health.
"Heart health is very important to protecting your brain, too," she said.
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