If you have high blood pressure and haven't treated it yet, consider this: getting it under control may also reduce your risk of dementia, suggests a study out Monday.

Men who had been treated with anti-hypertensive drugs were found in autopsies to have fewer microinfarcts (a sign of small strokes), fewer amyloid plaques and tangles (signs of Alzheimer's disease) and less brain atrophy.

Those on beta blockers, one of the least recommended medicines because of their side effects, had the healthiest brains, compared with other treatments. They had "about half as severe damage,'' says lead author and physician Lon White, but anyone who was treated "fared better than those who had no treatment.''

"What we're seeing is another advantage of treating hypertension,'' says White, of the Pacific Health Research and Education Institute in Honolulu. "It reduces heart disease and stroke, but we're saying it looks like it can also reduce all kinds of dementia."

About 1 in 3 U.S. adults, an estimated 68 million, have high blood pressure and about half of them don't have it under control, according to the Centers for Disease Control and Prevention. Called the silent killer, hypertension has no symptoms or warning signs, and many people don't know they have it.

Blood pressure is measured by two numbers: systolic (blood pressure in veins when the heart is pumping) and diastolic (blood going through the heart when it is at rest). Normal blood pressure is when systolic is below 120 and diastolic is below 80.

The findings are being presented in March at the American Academy of Neurology's annual meeting. The report is posted on the AAN website.

The study involved 774 Japanese American men who took part in the Honolulu Asia Aging Study, one of the "largest group of brain autopsies'' ever done in research, White said. The only way to confirm most dementias is by autopsy findings.

The brain relies on healthy arteries to deliver a steady supply of blood. Hypertension damages the arteries, by turning an open and flexible channel into a thick and stiff one, known as arteriosclerosis. Two kinds of dementia, vascular dementia and mild cognitive impairment, occur from a narrowing and blockage of the arteries brought on by high blood pressure. Also, brain damaging strokes can occur after blood clots form in arteries and interrupt blood flow.

Beta blockers are not the first line of treatment for high blood pressure, according to guidelines issued by the Joint National Committee on the Prevention, Detection and Treatment of High Blood Pressure. Researchers not associated with the study say that in most instances, they're often the last recommended treatment and in some countries they're little used because of their side effects and complications they cause in managing other diseases, such as diabetes. Beta blockers can increase the risk of stroke in the elderly and they can cause confusion and erectile dysfunction, according to Sripal Bangalore, a cardiologist and assistant professor of medicine at the NYU Langone Medical Center in New York, who was not associated with the new study.

"This study raises more questions than it answers, but nevertheless it calls for randomized trials to test these associations between beta blockers and their protection against dementia,'' Bangalore says. "The timing of this study is interesting because new guidelines to treat hypertension are expected to come out this spring."

"Maybe we need to think more about using beta blockers to help control dementia," says JoAnne Foody, co-director of cardiovascular wellness and prevention cardiology at Brigham and Women's Hospital in Boston.

Beta blockers slow the heartbeat, reduce the force of the heart muscle's contractions, and decrease blood vessel contraction in the heart, brain and the rest of the body. Other drugs -- such as diuretics, ACE inhibitors and calcium channel blockers -- treat hypertension in other ways.

Most patients require a "cocktail of multiple drugs" to treat hypertension, says Foody.

White says he hypothesized that he'd see the results between beta blockers and microinfarcts, but was surprised he found a lower number of amyloid plaques and tangles in Alzheimer's patients.

"My thought was maybe if you lower heart rate, you'd have less arteriosclerosis over the decades,'' says White. " My guess was that the accumulated injury over the years was less. But we don't really know why. Maybe the heart needs a little less pounding later in life."

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