A new study proclaims some dramatic benefits of using medication to lower blood pressure, but some scientists are advising caution.
Aggressive treatment of high blood pressure comes with risks, and the study, a large clinical trial sponsored by the National Institutes of Health, has not yet been peer-reviewed or published.
Until then, changes to blood pressure guidelines and patient treatment plans should wait, says Sripal Bangalore, a cardiologist at New York University Langone Medical Center.
“The results look good, there’s no doubt about it,” he says. “But we need more details. We need to look at the data.”
Some experts caution that the study’s results may not be as impressive as they initially seem, and that NIH didn’t release enough data to put the findings in context. Plus, a low blood pressure treatment plan might not be right for every patient.
On September 11, the National Heart, Lung and Blood Institute in Bethesda, Md., released the preliminary results of the Systolic Blood Pressure Intervention Trial, or SPRINT. This multiyear study used medications to lower the systolic blood pressure of participants to one of two targets: less than 120 millimeters of mercury or less than 140.
Keeping patients at a lower blood pressure reduced rates of cardiovascular events (such as heart attack and heart failure) and stroke by almost a third, compared with keeping patients at 140. And compared with the higher target group, the death rate in the 120 group was cut by almost a quarter.
“The preliminary results are terrific,” says American Heart Association president Mark Creager. For healthy people, he says, the heart association has long felt that systolic blood pressure should be 120 or lower. SPRINT’s results “provide the evidence to support that position.”
Previous studies have suggested that low blood pressure is linked to low risk of cardiovascular disease, says Paul Whelton, a clinical epidemiologist at Tulane University in New Orleans and the chair of SPRINT’s steering committee. “The question was, ‘How low should we go?’” when treating people with high blood pressure, he says.
SPRINT’s goal was to find out. The study began in 2009 and included 9,361 people age 50 and older. Each participant had a blood pressure of 130 or higher, and at least one other risk factor for cardiovascular disease. Researchers split the participants into two groups and gave them, on average, two medications to lower blood pressure to the 140 target, or three medications to hit the 120 target. Throughout the study, an independent group, the Data Safety and Monitoring Board, kept track of participants’ welfare.
Before SPRINT’s planned end date in the fall of 2016, the monitoring board saw a striking trend: People in the lower blood pressure group seemed to fare better than those in the higher group. The difference was so dramatic, Whelton says, that the board decided the intervention should be stopped. “It just didn’t seem ethical to continue the study.”
So NIH ended the trial on August 20, a year ahead of schedule.
Had scientists let the trial run its course, Bangalore says, they might not have seen such dramatic results. “We’ve seen this time and time again in prematurely terminated trials,” he says. “The relative risk reduction is usually exaggerated.”
What’s more, the heart, lung and blood institute reported only relative numbers, says Joel Handler, an internist at Kaiser Permanente in Anaheim, Calif. For people maintaining a blood pressure of 120, he says, “we don’t know what the absolute benefits are.” It’s not clear just how much the treatment lowers someone’s risk of having a heart attack, he says. “Is this a fraction of a percent, or is it more than that?”
If the preliminary data from SPRINT hold up, Handler says, adopting the new blood pressure target is the right thing to do. But a lower target might not be for everyone. If elderly patients’ systolic pressure drops too low, he warns, they may be more likely to fall and hit their heads.
Though blood pressure drugs are very safe, Whelton says, “typically when we prescribe blood pressure medication, it’s for a lifetime.”
People taking more medications may have more side effects, Bangalore says. Patients may also be less likely to stick to treatment plans. “Some patients might say, ‘Look, I’m already taking 20 medications. I don’t want to take more.’”
Bangalore is looking forward to seeing more details when the paper is published. That should happen within the next few months, the heart, lung and blood institute reports.
The heart association and the American College of Cardiology anticipate putting out new blood pressure guidelines in 2016, Whelton says. “We will of course be looking at SPRINT very carefully.”