ATLANTA -- Treating people who don't yet have high blood pressure but are well on their way to it can delay the condition but not permanently prevent it unless drugs are taken for life, new research suggests.
It is the first extensive study of treating prehypertension, a condition 45 million Americans have, defined as blood pressure readings from 120 over 80 up to 139 over 89. Below that is considered normal and above it, high.
High blood pressure greatly raises the risk of heart failure, stroke, heart attacks, and other medical problems. Doctors had hoped that two years of early treatment could permanently halt the progression from prehypertension to that more dangerous state.
The study suggests they may not have started early enough.
''We may need to rethink what we consider a normal blood pressure," said Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute.
Dr. Stevo Julius of the University of Michigan in Ann
Researchers gave 391 people the drug and 381 others phony pills for two years, then had everyone take placebos for two more years.
During the first two years, 154 people on the fake pills developed high blood pressure versus only 53 given the drug. In the next two years when those on the drug went off, however, 155 developed high blood pressure, matching what happened in the first two years in the placebo group.
This suggests the disease was just delayed, said Dr. James Stein, a University of Wisconsin-Madison cardiologist who had no role in the research.
''Once people stop therapy, blood pressure goes up inexorably, so I'm not sure we can prevent hypertension," he said.
Results were presented yesterday at an American College of Cardiology meeting and published online by the New England Journal of Medicine.
Although the study was paid for by a drug company, it is ''very important" and will be strongly considered when federal guidelines are next reviewed, Nabel said. Guidelines now advise the treatment begin when the ''big number" hits 140, but study participants who had ''high normal" readings averaging 134 were too far down the road to derail the disease, she said.
The study also supports the growing realization that ''high" blood pressure is a continuum rather than an arbitrary threshold, said Dr. Tom Giles, president of the American Society of Hypertension.
''You can't just look at the number. The disease process is in place before the blood pressure actually goes up at all," he said.
Blood pressure also tends to rise with age. Julius said study participants were relatively young; the average age was 48. ''But I wish they had been much younger than that" because they appeared to need treatment sooner, Julius said.
Specialists said lifestyle changes such as increasing water intake and eating right are key to controlling blood pressure.