A major new study shows treating high blood pressure more aggressively than usual cuts the risk of heart disease and death in people over age 50, the National Institutes of Health said Friday.

How tightly to control hypertension is controversial, especially as people get older. But the study's preliminary results showed strong enough benefits that NIH stopped the research about a year early.

"More intensive management of high blood pressure in people 50 years and older can save lives and reduce cardiovascular complications such as heart attacks," said Dr. Gary Gibbons, director of the NIH's National Heart, Lung and Blood Institute, which sponsored the study.

An estimated 1 in 3 adults in the U.S. has high blood pressure, raising the risk of heart attacks, stroke, kidney failure and other health problems. Normal blood pressure is less than a measurement of 120 over 80. High blood pressure is diagnosed once that measurement reaches, or passes, 140 over 90. Only about half of the nation's hypertension patients have their blood pressure under control.

But how low should their blood pressure be? Guidelines are mixed but generally have recommended getting that top number — called the systolic pressure — to about 140 in otherwise healthy adults, and to 130 in patients who also have kidney disease or diabetes.

The new study suggests lower may be better.

Starting in 2010, the SPRINT study — the Systolic Blood Pressure Intervention Trial — enrolled more than 9,300 people 50 and older who were deemed at increased risk for heart or kidney disease.

Half received an average of about two medications with the goal of lowering their systolic pressure below 140. The other half received an average of three medications with the goal of getting below 120.

The patients who reached that lower level saw their risk of death drop by almost 25 percent compared to the less aggressively treated patients, the study investigators said. Their rates of cardiovascular problems dropped by almost 30 percent.

It's too early to know if this one study might change current guidelines. Hypertension patients who don't have their blood pressure that low today should discuss their care with their doctors, researchers advised.

"We need to avoid having patients jump on it and demand that their blood pressure be normalized. That would be premature," cautioned Dr. Suzanne Oparil of the University of Alabama at Birmingham, one of the study investigators.

Researchers wouldn't give precise numbers of deaths and other complications, information expected when the full study results are published by year's end. Nor did they provide information on side effects except to say that the study's safety monitors weighed that information in advising NIH that the benefits were strong enough to stop it early.

Researchers will continue to track the SPRINT participants to see if kidney disease, cognitive function and dementia also were affected by more aggressive care.