Blood pressure study debunks basic assumptions
Research shows previous 140mm standard must drop to 120mm, writes GINA KOLATA
WHEN the federal government announced in September that it had halted a large blood pressure study because its results were so compelling, doctors were left in frustrating limbo.
The announcement said researchers had found that driving systolic blood pressure to levels far below what current guidelines recommend — less than 120mm instead of 140mm or 150mm of mercury — could save lives and prevent heart disease and strokes. But they declined to release data on the number of lives saved, number of heart attacks prevented, or other critical measures.
“How can anyone do anything different tomorrow with regard to blood pressure control without knowing more about what they found?” asked Harlan Krumholz, a cardiologist at Yale, echoing the concerns of other specialists.
On Monday, reporting at an American Heart Association meeting in Orlando, Florida, and in a paper published simultaneously in The New England Journal of Medicine, study investigators lifted the veil.
Among the 9,361 hypertension patients followed for an average of 3.2 years, there were 26% fewer deaths (155 compared with 210) and 38% fewer cases of heart failure (62 compared with 100) among patients who achieved the systolic pressure target of 120 than among those who achieved the 140 target.
SYSTOLIC pressure is the higher of the two blood pressure numbers and represents pressure on blood vessels when the heart contracts. Overall, there was a 24% reduction — 243 compared with 319 — in people who had a heart attack, heart failure or stroke or died from heart disease, Paul Whelton, a principal investigator for the study, said. The older participants did just as well as younger ones.
For millions of Americans with high blood pressure, the results could be transforming, said Marc Alan Pfeffer, a cardiologist at Brigham and Women’s Hospital in Boston.
Before now, Pfeffer said, if a patient older than 50 came into his office with systolic pressure of 136 and a well-controlled risk factor for heart disease such high cholesterol, he would pat the patient on the back and say, “Great job”. Now, he said, he would feel obliged to give the patient more hypertension drugs.
At least 17-million Americans would be affected by the findings, said Paul Muntner, an epidemiologist at the University of Alabama who was not involved with the study.
The study, called Sprint, enrolled patients aged 50 and older with high blood pressure. The patients also had at least one other risk factor for heart disease such as smoking or a high cholesterol level, kidney disease, or they were simply 75 or older. Half were assigned to a systolic pressure target below 140, in keeping with today’s medical practice. The rest were assigned a target pressure of less than 120. The study was supposed to continue until 2017, but ended when researchers said they had “potentially lifesaving” results.
Doctors have long wrestled with how low blood pressure should go. Bringing it too far down, particularly in the elderly, can result in complications such as dizziness and fainting.
According to the results, about 5% of the patients, or 220 people, with the 120 blood pressure target had serious complications over the course of the study — blood pressure so low it caused severe dizziness or fainting, or a reversible injury to the kidneys. Among those with the 140 target, 118 had serious complications.
A complication the investigators worried about with blood pressures of 120 or lower — an abrupt drop in blood pressure when people stood up — occurred more often in those with the higher systolic pressure target.
“When we put those complications in the context of a 27% reduction in total mortality, it seems that the benefits outweigh the risks,” said biostatistician David M Reboussin, a principal investigator for the study.
What was most remarkable, researchers said, was that the improvements in death rates and rates of heart attacks occurred on top of improvements these patients experienced as their blood pressures fell to 140. To get their systolic pressures to 120, patients took an average of one additional blood pressure drug — 2.8 pills instead of 1.8.
It is now up to committees that formulate guidelines to decide how to change their recommendations.
ONE issue is what to tell patients with diabetes, who were not included in this study. A previous study with diabetics that tested stringent blood sugar control along with a blood pressure of 120 found no reduction in heart attacks or deaths. But many researchers are not convinced that it proved that lower systolic pressure failed to help people with diabetes, because it was so much smaller and because blood sugar control was also being tested.
Another question is what to advise people younger than 50 and those older than 50 with no risk factors other than high blood pressure. “That will be a judgment call,” said Jackson T Wright Jr, a study investigator who also is on the guidelines committee and who directs the hypertension programme at University Hospitals Case Medical Center in Cleveland.
There also is the unanswered question of how low blood pressure should go. A few patients in the new study lowered their systolic pressure to 110, but getting it below 120 was a challenge for most people.
Wright said that it was almost inconceivable that there would be another large study comparing, say, a blood pressure of 110 to one of 120.
“That is a very narrow window,” he said, and the expected differences in outcomes would be small, meaning the study would have to be very large and prolonged.