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

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

Thoseon beta blockers, one of the least recommended medicines because oftheir side effects, had the healthiest brains, compared with othertreatments. They had "about half as severe damage,'' says lead authorand physician Lon White, but anyone who was treated "fared better thanthose who had no treatment.''

"What we're seeing is anotheradvantage of treating hypertension,'' says White, of the Pacific HealthResearch and Education Institute in Honolulu. "It reduces heart diseaseand stroke, but we're saying it looks like it can also reduce all kindsof 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 undercontrol, 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 ismeasured by two numbers: systolic (blood pressure in veins when theheart is pumping) and diastolic (blood going through the heart when itis at rest). Normal blood pressure is when systolic is below 120 anddiastolic 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.

Thestudy involved 774 Japanese American men who took part in the HonoluluAsia Aging Study, one of the "largest group of brain autopsies'' everdone in research, White said. The only way to confirm most dementias isby autopsy findings.

The brain relies on healthy arteries todeliver a steady supply of blood. Hypertension damages the arteries, byturning an open and flexible channel into a thick and stiff one, knownas arteriosclerosis. Two kinds of dementia, vascular dementia and mildcognitive impairment, occur from a narrowing and blockage of thearteries brought on by high blood pressure. Also, brain damaging strokescan occur after blood clots form in arteries and interrupt blood flow.

Betablockers are not the first line of treatment for high blood pressure,according to guidelines issued by the Joint National Committee on thePrevention, Detection and Treatment of High Blood Pressure. Researchersnot associated with the study say that in most instances, they're oftenthe last recommended treatment and in some countries they're little usedbecause of their side effects and complications they cause in managingother diseases, such as diabetes. Beta blockers can increase the riskof stroke in the elderly and they can cause confusion and erectiledysfunction, according to Sripal Bangalore, a cardiologist and assistantprofessor of medicine at the NYU Langone Medical Center in New York,who was not associated with the new study.

"This study raises morequestions than it answers, but nevertheless it calls for randomizedtrials to test these associations between beta blockers and theirprotection against dementia,'' Bangalore says. "The timing of this studyis interesting because new guidelines to treat hypertension areexpected to come out this spring."

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

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

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

Whitesays he hypothesized that he'd see the results between beta blockersand microinfarcts, but was surprised he found a lower number of amyloidplaques and tangles in Alzheimer's patients.

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