HIGH BLOOD PRESSURE

Having our blood pressure taken is a ritual with which we are all familiar. Most of us know our blood pressure—120/80, 135/95, or whatever. But what do the numbers actually mean? Blood pressure is simply the force exerted by the bloodstream against the walls of the arteries. Traditionally, it is expressed as a ratio, a larger number over a smaller one, for example, 120 over 80, usually written as 120/80, although the ratio between the two is irrelevant. What blood pressure of 120/80 means is this: the pressure when the heart contracts to pump blood to the arteries can drive a column of mercury up a tube to a height of 120 millimeters, known as the systolic, or pumping pressure. And when the heart relaxes between beats, the pressure exerted can support a column of mercury only 80 millimeters high, called the diastolic, or resting pressure.

Blood pressure is measured with an instrument called a sphygmomanometer, which is Greek for “pulse-pressure measurer.” Usually a nurse wraps an inflatable cuff around your upper arm. Squeezing a rubber bulb, she pumps air into the cuff, which cuts off the blood flow to your lower arm. She then opens a valve and gradually releases the air. As she does, she listens with a stethoscope placed on an artery just below the cuff for a thumping sound that signals that the blood has started to flow again. The level of the mercury when she hears the first thump is your systolic pressure.

As the air is released and the cuff loosens its grip, the sound softens, eventually disappearing, signaling that your blood flow is no longer impeded, even in the heart’s resting stage. The mercury level at the instant the thumping sound disappears is your diastolic pressure.

Generally speaking, the lower your blood pressure the better off you are. Readings between 110/75 and 140/90 are considered normal, but research has shown that people who live to advanced ages almost always have low blood pressure.

One of the myths about blood pressure is that it rises inevitably as we age. There seems little truth to this notion, especially when it comes to the more critical measurement, the diastolic pressure. But whether or not blood pressure tends to rise in older folks, such rises should not be treated as benign. Studies have found that older people with blood pressures of 140/90 or below live longer and have fewer strokes, heart attacks, and instances of heart failure than those whose pressures are even slightly higher.

The Silent Killer

High blood pressure is often called a silent killer: silent because even people with extremely high readings may experience no symptom of the disease; and killer because hypertension is one of the leading precipitators of heart attack, congestive heart failure, stroke, and kidney disease.

About one third of adult Americans—some 60 million people—are hypertensive to some degree. Even if you suffer from mild hypertension only, which begins as you cross 140/90, your risk of contracting heart disease is considerably greater than if your reading is below 140/90. Moderate high blood pressure—readings between 145/95 and 160/115—results in even greater risk. If your blood pressure measures 160/115 or over, you have severe hypertension and are shortening your life every day you leave your blood pressure at that level.

Controlling Hypertension

Fortunately, in most cases, hypertension can be controlled. A good first step? Swim.

Large clinical studies have shown that regular aerobic exercise combined with meditation or relaxation (such as Dr. Herbert Benson’s famous “relaxation response”) is very effective in lowering blood pressure for most people with high blood pressure. And no aerobic exercise is more effective in inducing a relaxed state than swimming.

My own experience provides a good example. I suffer from what doctors call essential hypertension, a tendency toward high blood pressure in the absence of any of the other factors doctors often find in hypertensive patients—obesity or high body fat, a lifetime of high cholesterol readings, an inactive life-style. When I was twenty-eight, before I began swimming again, my blood pressure consistently measured about 140/96—a high reading for a young man and one that signaled danger for the future. Because it involves no correlating factors, many doctors find essential hypertension the most intractable to treatment other than drug therapy. Yet within months after I began swimming, my blood pressure had declined to 130/90. Today, twenty-two years later, my blood pressure is a very healthy 116/74.

Because most antihypertensive drugs produce unpleasant side effects in many people, the first step the doctor will recommend for most people with high blood pressure is losing weight or, more precisely, lowering body fat percentage. The belief is that less fat in the diet will lead to less fat in the blood, which in turn will lead to less plaque formation on the inside walls of the arteries. As Chapter 4 will show, swimming is an effective way to reduce body fat. At one time it was thought that salt consumption was a major cause of hypertension and that reducing it would lower blood pressure. But researchers now believe that for many people who do not eat a high-salt diet, further reducing salt is not likely to bring about lower blood pressure.

So if you want to keep your blood pressure down, here is the two-pronged prescription. Swim, and set aside some time to relax each day. True, it takes a bit of self-discipline. But this is your life we are talking about, and these changes will make your life more pleasurable as well as longer. The alternative, drug therapy, may seem easier, but it is not very attractive over the long haul: a lifelong dependency on chemicals, most of which cause drowsiness, dry mouth, fatigue, skin disorders, or impotence in many people.