New evidence from the National Heart, Lung, and Blood Institute's Framingham Heart Study finds that systolic blood pressure, far more than diastolic blood pressure, identifies patients with hypertension, determines their blood pressure stage, and indicates the need for treatment, but both measurements used together are best. The study is published in the September issue of Hypertension.
"The message from this study is that you cannot ignore systolic pressure," said Claude Lenfant, M.D., NHLBI Director. "For years, treatment strategies have focused on lowering a patient's diastolic pressure, because diastolic pressure accurately predicted heart disease and stroke risk in younger patients. But this practice excludes the elderly, who tend to have higher systolic pressures and lower diastolic pressures - and who have the least-controlled blood pressure of all patients."
Systolic pressure measures the force blood exerts on the artery walls when the heart beats, and diastolic pressure measures the force on the arteries between heartbeats. Hypertension is diagnosed when the systolic blood pressure is 140 mm Hg or higher or the diastolic blood pressure is 90 mm Hg or higher. Patients are classified into stages of hypertension depending on how high or low their blood pressure is.
There are 50 million adults in the United States with hypertension. Currently, only 68 percent of them are aware of their condition, 54 percent are being treated, and only 27 percent have it under control.
The Framingham researchers examined nearly 5,000 untreated men and women, average age 58, and determined each person's blood pressure stage using both systolic and diastolic pressure together as recommended in the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI). NHLBI's National High Blood Pressure Education Program issued the JNC VI guidelines in 1997.
Researchers then compared these blood pressure stage classifications with those obtained from using only the systolic pressure or only the diastolic pressure to see which method would come closest to the JNC VI stage classification. They found that systolic blood pressure alone correctly classified the blood pressure stage in about 96 percent of patients, while diastolic pressure alone classified only 68 percent of patients correctly. Among patients over age 60, researchers found that systolic pressure alone correctly classified 99 percent of patients, whereas diastolic alone correctly classified only 47 percent.
The Framingham Heart Study researchers agree that both measurements are important in identifying and treating patients with high blood pressure, but suggest that future blood pressure treatment guidelines might consider a greater emphasis on the systolic pressure.
The National High Blood Pressure Education Program of the NHLBI will issue an update of the JNC VI in the form of a Clinical Advisory on Systolic and Pulse Pressure this fall, based on this and other recent research that confirms the importance of identifying, treating and controlling systolic hypertension.
For more information on the detection, prevention and treatment of high blood pressure, visit the National Heart, Lung, and Blood Institute's Web site at http://www.nhlbi.nih.gov .
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