WEDNESDAY, March 17, 2010 (HealthDay News) -- In the ongoing struggle to find treatments -- and maybe one day even a cure -- for dementia, researchers are focusing their attention on high blood pressure, long a culprit for a variety of other ills and an ailment for which many drugs are already available.
This coming fall, the U.S. National Institutes of Health will start enrolling participants in the largest trial thus far to see if lowering blood pressure even below current recommendations can reduce not only the risk of age-related cognitive decline, but also the risk of cardiovascular and kidney diseases.
The Systolic Blood Pressure Intervention Trial (SPRINT) will involve 7,500 people aged 55 and over who will be followed for a minimum of four years. The NIH is investing $114 million in the endeavor.
"We have a number of effective and safe medications to lower blood pressure," said Dr. Lawrence Fine, chief of the clinical applications and prevention branch in the division of cardiovascular sciences at the National Heart, Lung, and Blood Institute. "For the average person right now, the recommendation is a blood pressure of 140/90 or lower. SPRINT will compare that with a goal of 120 as the top number. Will the rate of dementia for people in the lower-goal arm be lower than standard?"
Current clinical guidelines recommend systolic pressure (the top number in a blood pressure reading) of less than 140 millimeters of mercury (mm Hg) for healthy adults, and 130 mm Hg for adults with kidney disease or diabetes.
"Hypertension is very easy to medicate and very easy to measure, so they want to see if just by modifying that simple thing they could reduce the incidence of dementia," said Ian Murray, an assistant professor of neuroscience and experimental therapeutics at the Texas A&M Health Science Center College of Medicine in College Station.
The timing is critical, as over the next several decades huge numbers of aging Baby Boomers will develop Alzheimer's disease and other forms of dementia.
Besides sparing thousands of Americans needless suffering, "if you could reduce that number by 10 percent, your cost savings would be immense," said William Thies, chief medical and scientific officer for the Alzheimer's Association in Chicago.
Although experts have long suspected a link between high blood pressure and dementia, without trial data those suspicions inevitably remain hypotheses.
"What we do know is that there's an association between high blood pressure and a higher rate of dementia -- it's not a large increased risk but there is some increase," Fine said.
"A whole bunch of epidemiologic data says there's a link, and one trial actually showed that if you lowered people's blood pressure it decreased the amount of dementia," added Thies.
That particular trial used blood pressure drugs known as calcium-channel blockers, one in an extensive armamentarium of medications for the condition. Still, no one really knows why treating high blood pressure would lower the odds of dementia if, in fact, it really does.
"We'd really like to know the answer because it would give us our first confirmed pathway to modifying the amount of dementia by treating people with known agents," Thies said. "That would be very important."
The SPRINT trial will randomize participants -- all of whom have systolic blood pressure of 130 mm Hg or higher -- either to a group taking more intensive drug therapy (three or four medications) to try to get their blood pressure under 120, or a control group taking about two medications to maintain blood pressure at the currently recommended 140.
"We may discover lower blood pressure will not reduce the rate of dementia, but if the lower goal did reduce the rate of dementia by 10 or 20 or 30 percent, that would be an important observation because we don't have other good treatments for dementia," Fine said. "SPRINT should provide some additional science to inform us whether lowering blood pressure to the lower goal will, in fact, reduce the rate of developing dementia."
"There are a lot of reasons why we ought to control blood pressure anyway, but this gives us another very important reason," Thies added.
There's more on high blood pressure at the American Heart Association.