Johns Hopkins Health Alerts Hypertension (High Blood Pressure) and Stroke Classifying Blood Pressure
With the publication of the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure—more commonly known as JNC 7—a new system of classifying blood pressure was adopted in 2003. This classification system has three categories: normal, prehypertension, and hypertension (stage 1 and stage 2).
Normal blood pressure. People with a blood pressure level less than 120/80 mm Hg have normal blood pressure.
- Prehypertension. People with a systolic blood pressure (the top number in a blood pressure reading) between 120 and 139 mm Hg or a diastolic blood pressure (the lower number) between 80 and 89 mm Hg have a condition called prehypertension. About one in four Americans has prehypertension.
If you have prehypertension, you are at increased risk for developing high blood pressure and complications of high blood pressure, such as heart attack and stroke. Lifestyle measures to reduce high blood pressure, such as losing weight, eating a diet rich in fruits and vegetables, reducing salt intake, increasing physical activity, moderating alcohol consumption, and quitting smoking can help lower the risk. For people with both prehypertension and diabetes, coronary heart disease, or kidney disease, medication may be needed to keep blood pressure below 130/80 mm Hg.
- High Blood Pressure. People with a systolic blood pressure of 140 mm Hg or higher or a diastolic blood pressure of 90 mm Hg or higher are considered to have high blood pressure. Lifestyle modifications and antihypertensive medication are required to lower blood pressure and reduce the risk of complications from high blood pressure. Lifestyle measures to reduce high blood pressure include losing weight if necessary, following the Dietary Approaches to Stop Hypertension (DASH) diet, reducing salt intake, increasing physical activity, moderating alcohol consumption, and quitting smoking
Most individuals with high blood pressure should aim to keep their blood pressure below 140/90 mm Hg. For those with diabetes, coronary heart disease, or kidney disease, blood pressure should be maintained below 130/80 mm Hg.
Systolic vs. Diastolic Blood Pressure
Historically, doctors focused on diastolic blood pressure for the diagnosis and treatment of high blood pressure. But today the focus is on both systolic and diastolic blood pressure, since systolic pressure is an important determinant of complications of high blood pressure, particularly in people older than age 50.In contrast to diastolic blood pressure, which tends to rise until about age 55 and then begins to fall, systolic blood pressure continues to rise with age. Previously, such elevations were thought to be a normal part of aging—caused by a gradual loss of elasticity in the arterial walls. Now, however, a substantial body of evidence shows that high systolic blood pressure with a diastolic blood pressure under 90 mm Hg carries a high risk of heart attack and stroke. In light of such findings, the JNC 7 guidelines recommend using systolic blood pressure as the standard measure for the evaluation and treatment of high blood pressure, especially for people age 50 and older.
Isolated High Systolic Blood Pressure
A high systolic blood pressure with a normal diastolic pressure is common in older adults. In fact, 65% of people over age 60 with high blood pressure have a condition called isolated systolic hypertension, defined as a systolic blood pressure of 140 mm Hg or higher and a diastolic blood pressure under 90 mm Hg. Isolated systolic hypertension is associated with an increased risk of stroke, coronary heart disease, and kidney disease.Pulse Pressure
Another possible predictor of high blood pressure complications is pulse pressure—the difference between the systolic and diastolic blood pressures. Pulse pressure reflects the stiffness of the arteries. When researchers pooled the results of three major high blood pressure studies involving nearly 8,000 patients, they found that the higher the pulse pressure, the greater the risk of cardiovascular complications (such as heart attack and stroke) and death from any cause.
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