NEW YORK, Jun 10 (Reuters) -- When it comes to preventing stroke and heart attack, the optimal blood pressure is lower than previously thought, according to a study of nearly 19,000 patients in 26 different countries.
Hypertension has been defined as a blood pressure of 140/90 or greater. But the new study indicates that to reduce the risk of cardiovascular disease, blood pressure should be at or below 138.5 mmHg systolic (the pressure when the heart is contracting) and 82.6 mmHg diastolic (the blood pressure when the heart muscle is relaxed) reported researchers Wednesday at the 17th scientific meeting of the International Society of Hypertension in Amsterdam, the Netherlands.
"What we've learned is that lowering blood pressure just to the point where it isn't 'high' isn't enough," said Dr. Claude Lenfant, director of the National Heart, Lung, and Blood Institute in a statement issued by the researchers. "If physicians lower blood pressure beyond traditional levels of 90 mmHg, there's reason to believe that cardiovascular morbidity and mortality can be diminished."
In the 5-year study, known as the Hypertension Optimal Treatment (HOT) Study, the patients all received the calcium channel blocker, felodipine, to treat their elevated pressure. Almost 70% of the patients also received beta-blockers and ACE inhibitors as needed and a small percentage also required diuretics.
The patients, who had an average age of 61 and a diastolic blood pressure between 100 mmHg to 115 mmHg at the study's start, were randomly assigned to three groups in which the target diastolic blood pressure was 90, 85, or 80 mmHg.
Those patients who lowered their diastolic pressure to 82.6 mmHg and their systolic pressure to 138.5 had a major reduction in cardiovascular events such as stroke or heart attack, according to Dr. Lennart Hansson of the University of Uppsala, Sweden, who reported the HOT results at the meeting. About 55% of the patients in the 80 mmHg were able to reach their target goal with the combination of drug treatments.
"The HOT study is an unprecedented effort to help physicians decide how low they should go when it comes to treating high blood pressure," said study co-author Dr. Kenneth Jamerson in the HOT statement.
"Many physicians believe it's unrealistic to try to achieve a diastolic blood pressure score of 80. We found that by using appropriate hypertension medications, blood pressure could be lowered to this number in the majority of patients," added Jamerson, who is an associate professor of medicine at the University of Michigan Medical Center's Division of Hypertension.
The study suggests that the benefits of blood pressure lowering may be even greater for diabetics. Of the 1,501 patients with pre-existing diabetes, those in the group targeted to reach a diastolic pressure of 80 mmHg had half the risk of a major stroke or heart attack compared with those in the 90 mmHg group. The HOT team found that the optimum blood pressure for diabetic patients is 135/80 mmHg or lower.
Overall, the findings suggest that physicians need to work to achieve a blood pressure plateau of 130 to 140 mmHg systolic and 80 to 85 mmHg diastolic in their patients, according to Dr. John Chalmers, former president of the International Society of Hypertension.
The study also confirmed that taking low-dose aspirin in addition to blood pressure-lowering drugs can reduce the risk of illness and death due to heart attack. Those who took 75 milligrams of aspirin daily had a 30% lower risk of heart attack -- without an increase in stroke risk -- compared with those who did not take aspirin.
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