High Blood Pressure - Recognizing And Reducing Risk Factors: Heart Disease

Content provided by the Faculty of the Harvard Medical School

High blood pressure

Your blood pressure reading has two parts. The systolic blood pressure (the top number) represents the pressure while the heart is beating and shows how hard the heart works to push blood through the arteries. The diastolic blood pressure (the bottom number) represents the pressure when the heart is refilling with blood between beats and shows how forcefully arteries are being stretched most of the time.

The higher your blood pressure, the greater your risk of suffering a heart attack, heart failure, stroke, or kidney disease. Yet too many people ignore the risk posed by high blood pressure. Recognizing this fact, a 2003 federal report — the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC7, for short) — urged Americans to take blood pressure more seriously and control it more aggressively. The report was intended to prod people out of their complacency about blood pressure. Why? Not enough people are aware they have high blood pressure or are at risk of developing it, and even many of those who are aware aren't doing enough to control it (see Table 2). In addition, an analysis of several large studies indicates that blood pressure levels previously considered normal are not low enough.

Under the old guidelines, published in 1997, your blood pressure was considered normal if it was less than 140/90 mm Hg, because that was the average or usual blood pressure in the United States. But several large studies show that the chance of developing coronary artery disease starts creeping up at 115/75 mm Hg — a level previously considered solidly in the "safe" range. From then on, the risk doubles every time the systolic pressure rises 20 points or the diastolic pressure rises 10 points.

On the other hand, the benefits of blood pressure control are substantial. Clinical trials have shown that treating hypertension reduces the incidence of stroke by 35%–40%, the incidence of heart attack by 20%–25%, and the incidence of heart failure by more than 50%.

Updated blood pressure goals

Given the evidence, the JNC7 guidelines not only redefined normal (meaning "optimal") blood pressure as anything under 120/80 mm Hg, but also introduced a new category, prehypertension, to identify people who might prevent or at least slow the onset of hypertension by adopting a healthier lifestyle (see Table 3).

So who is at risk? Almost everyone will be at some point. About 60% of American adults currently have high blood pressure (either prehypertension or hypertension). And data from the Framingham Heart Study indicate that people who are 55 years old and have normal blood pressure face a 90% chance of developing high blood pressure as they get older, unless they take preventive steps.

When to be tested. Because hypertension usually begins gradually between ages 20 and 50, all adults should have their blood pressure checked regularly. Blood pressure checks every two years might suffice for people with normal levels. But people with elevated blood pressure need more frequent measurement — once a year for those with prehypertension, and sometimes even more frequently in people with hypertension.

How low to go. For people with hypertension, JNC7 defines good control as getting your blood pressure under 140/90 mm Hg. But people with diabetes or chronic kidney disease should aim for an even lower level, below 130/80 mm Hg.

To prevent or treat hypertension, the first step is to adopt healthier habits (see "Lifestyle changes to protect yourself"). Even with lifestyle changes, however, many people with hypertension also need medications to treat the disorder (see "Blood pressure medications").

Last updated:	May 03, 2007