Harvard Men's Health Watch

Prehypertension: Does it really matter?

Dr. Scipione Riva-Rocci started it all in 1896, when he perfected the sphygmomanometer, or blood pressure cuff. As doctors took blood pressure readings on millions of people over the years, it became clear that hypertension is a major threat to health, increasing the risk of stroke, heart attack, congestive heart failure, kidney failure, and visual loss. And as data accumulated, it also became clear that there is no bright line between a healthy blood pressure and a harmful one; in general, the lower the pressure, the better.

Nevertheless, doctors need a target for blood pressure, and patients also need a goal. Those goals changed in 2003, when the authoritative Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure issued its Seventh Report (JNC 7). The report set the threshold for a normal blood pressure reading lower than ever before, at 120/80 millimeters of mercury (mm Hg), and it also established a new diagnostic category of "prehypertension" (see table).

Classification of blood pressure for people 18 years or older

Classification

Systolic BP

Diastolic BP

Normal

below 120

below 80

Prehypertension

120""139

80""89

Stage 1 hypertension

140""159

90""99

Stage 2 hypertension

160+

100+

Systolic blood pressure (BP) is the number recorded when the heart is pumping blood into the arteries; diastolic BP is the number recorded while the heart is refilling with blood between beats. All units are in mm Hg.

Which number?

The revised standards provide simple guidelines for interpreting blood pressure readings, but each reading generates two numbers. What if your systolic and diastolic readings contradict each other? To determine your classification, use the number that puts you in the higher group. For example, if your reading is 114/84, you have prehypertension.

Each person has two arms; pressure readings often differ between them, sometimes by 10 mm Hg or more. Which arm should you use to determine your classification? It's not a question of right vs. left but of right vs. wrong: Use the arm with the higher reading.

Blood pressure readings can vary from time to time. Should you worry about your peaks or take comfort from your valleys? The JNC 7 classification depends on your usual or average blood pressure rather than occasional extremes. For most people, a careful reading during an annual checkup will suffice. But men with prehypertension or hypertension should have their readings checked more often to get a true picture. And since readings can vary in different settings, it's important to consider the type of measurement in determining a category. When 24-hour ambulatory monitoring is used, waking-hour values above 135/85 are hypertensive, as are values above 120/75 during sleep. And people who check their own blood pressures at home should be considered hypertensive if their average or usual readings exceed 135/85.

If you suspect that these methods are rigged to put you in the highest possible category, you're right. The goal is not to reassure people but to identify everyone who can benefit from treatment. And the revised standards recognize that both systolic and diastolic pressures count. After years of believing that the diastolic pressure was more important, doctors now know that the systolic value is actually a better predictor of risk, especially in people over 50.

A new diagnosis

According to estimates using the revised JNC 7 standards, some 59 million American adults have prehypertension. Most feel perfectly well and have normal heart, kidney, and brain function. With so many apparently healthy people in the category, is prehypertension a real illness?

It's not an illness "" but it is an important warning that illness lies ahead.

For one thing, prehypertension increases the risk of developing hypertension, a major illness indeed. According to a 2005 analysis by the Framingham Heart Study, people with prehypertension are twice as likely to develop high blood pressure as are people with normal pressures.

Even worse, prehypertension increases the risk of heart disease. The same study reports that men with prehypertension are 3.5 times more likely to suffer heart attacks than those with normal blood pressures. Surprisingly, although high blood pressure is a major cause of strokes, prehypertension did not appear to increase the risk of stroke.

Boyish blood pressures: A head start to heart disease?

For many years, doctors have known that the male gender is a risk factor for coronary artery disease. In the United States, heart disease is the leading killer of both men and women, but the average man develops heart disease 10 years earlier than the average woman, and serious events such as heart attacks strike men some 20 years before they threaten women. Many things contribute to the heart disease gap, ranging from the higher HDL ("good") cholesterol levels in women, the different effects of testosterone and estrogen, and lifestyle differences ranging from diet and exercise to stress and smoking. And a 2006 study adds another explanation: blood pressure levels in youth.

The subjects were 320 males and 337 females between the ages of 7 and 30. Twenty-four-hour blood pressure readings were obtained from each person an average of five times a year over 15 years. Even in childhood, males had significantly higher average diastolic blood pressure levels than females. Males also experienced a faster rise in blood pressure readings over time than females. These gender differences remained valid after taking factors such as height, body mass index (a measure of obesity), socioeconomic status, stress-related coping styles, and family history of hypertension into account.

Atherosclerosis begins in youth. In males, a little boost in blood pressure may help explain their unfortunate head start in this common and serious disease.

What to do?

First, know your blood pressure. That means having it measured by a health care professional or measuring it yourself with a high-quality home blood pressure machine. The American Heart Association calls hypertension the "silent killer" because it can do great damage to the arteries in your body before producing any symptoms at all. With the new information at hand, prehypertension may also earn that ominous name. Don't count on headaches, nosebleeds, a red face, or mental stress to warn you that your pressure is too high "" none of these traditional signs is reliable. Instead, have your pressure measured with every check-up; once a year is ideal.

Second, find out if you have other cardiovascular risk factors such as abnormal cholesterol levels, diabetes, a sedentary lifestyle, obesity, tobacco abuse, and mental stress. A 2004 study of 9,087 people enrolled in the second National Health and Nutrition Examination Survey found that prehypertension was linked to a 1.27-fold increase in the overall mortality rate. But virtually all of the excess mortality was explained by the presence of other cardiac risk factors. Similarly, a 2006 report from the Atherosclerosis Risk in Communities Study found that prehypertension more than doubles the risk of heart disease and that the risk is even greater for people with diabetes or obesity. Correcting these abnormalities should go a long way toward reducing the health burden of prehypertension.

Treatment

For most prehypertensives, treatment should depend on lifestyle changes, not medications. Here's what to do:

Diet. The Dietary Approaches to Stop Hypertension, or DASH, program is best. It involves a reduction in dietary sodium to 2,300 mg a day or less. The less salt in your diet, the better; 1,500 mg a day is the tough new goal for people with hypertension and for everyone who is middle-aged or older. The DASH diet also calls for a low consumption of animal fat and processed foods. But you'll still have plenty to eat, for the diet includes many fruits, vegetables, whole grains, and low- or nonfat dairy products. This diet can lower your systolic blood pressure by 10""22 mm Hg.

Exercise. You don't have to spend hours in a gym or train for a marathon. In fact, as little as 30 minutes of moderate exercise, such as brisk walking, will produce enormous benefits "" as long as you do it nearly every day. A 2005 study reported that moderate physical activity was more effective in lowering the blood pressure of people with prehypertension than in people with normal pressures. In all, exercise should lower your systolic pressure by 4""9 mm Hg.

Weight control. One of the most important ways to reduce blood pressure, it's also one of the hardest to achieve. Despite the claims made by diet books, plans, and supplements, there is no quick fix. But there is a slow fix: a calorie-restricted healthful diet, such as DASH, plus regular exercise. An obese person who sheds 20 pounds can expect a 5""20 mm Hg drop in systolic pressure.

Moderate alcohol use. Small amounts of alcohol won't raise your pressure, but heavier drinking will. If you choose to drink, limit yourself to two drinks per day, counting 5 ounces of wine, 12 ounces of beer, or 1½ ounces of spirits as one drink; for smaller men (and women), one drink a day may be a wiser limit.

Low-dose alcohol appears to reduce the risk of heart disease and stroke, but no one should take up drinking strictly for its medical benefits. Still, men who choose to drink moderately and responsibly may well be drinking to their health. People who reduce heavy drinking can shave at least 2""4 mm Hg off their systolic blood pressures.

Stress control. It's harder to quantify than the other lifestyle goals, but a number of studies suggest that meditation and other relaxation techniques can help lower blood pressure. Mental tension and hypertension are not synonymous, and plenty of laid-back folks have high blood pressure. But if you are under stress, winding down is likely to help your health.

Bad habits, including poor nutrition, lack of exercise, and alcohol abuse, are responsible for America's alarming rise in chronic diseases such as obesity and diabetes. They also contribute mightily to our epidemic of hypertension. Healthful living will prevent many cases of high blood pressure, and it can replace or reduce medications for many hypertensives. But many others often need medication despite clean living. Fortunately, drug therapy is better than ever.

Medication. A well-publicized 2006 study reported that two years of treatment with the angiotensin receptor blocker candesartan (Atacand) can reduce the likelihood that prehypertension will progress to hypertension, with the benefit persisting for at least two years after treatment is stopped. But more research is needed to confirm this observation and to find out if it translates to actual cardiovascular protection.

Should you take medication for prehypertension? It's an important question, but doctors don't know the answer. They do know that readings below 120/80 are best, but they don't know if medication should be used to reach that low goal. Studies that compare the risks and benefits of drug treatment will be needed to settle the issue for most people with prehypertension. But even now, patients with diabetes, chronic kidney disease, and heart disease should take medicine if that's what's needed to bring their pressures below 130/80. Although that's not quite normal, it's clearly beneficial; perhaps doctors should call it "prenormal."