High Blood Pressure

High blood pressure (hypertension) is blood pressure that is consistently higher than normal. Blood pressure is the force exerted by blood against the walls of arteries (the blood vessels that carry blood from the heart to the rest of the body).

The "tension" part of "hypertension" does not imply being tense or anxious. Many people who are calm and relaxed have hypertension, and some people who are tense and anxious have normal blood pressure. Also, the "hyper" part of "hypertension" does not imply being hyperactive.

In the United States, high blood pressure becomes more common as people age. More than half of people aged 65 or over have high blood pressure.

Persistently high blood pressure damages arteries. It speeds up the deposit of cholesterol and other fatty materials in arteries (atherosclerosis). It may make arteries weaken and sometimes even bulge and rupture. It may cause the heart to enlarge. As a result, tissues (particularly in the brain, heart, and kidneys) are damaged, sometimes resulting in an early death. As blood pressure increases, the risk of stroke, heart attack, heart failure, and kidney failure also increases. Rarely, very high blood pressure impairs vision. Treatment can effectively control high blood pressure and help prevent the problems it causes.

When a person's blood pressure is measured, the result consists of two numbers. The higher number (systolic pressure) represents the pressure when the heart beats. The lower number (diastolic pressure) represents the pressure when the heart relaxes between beats. Ideally, blood pressure is about 120/80 mm Hg (millimeters of mercury). This reading is referred to as "120 over 80." Blood pressure (often abbreviated BP) is considered high when the systolic pressure is 140 mm Hg or higher or when the diastolic pressure is 90 mm Hg or higher. In younger people with high blood pressure, both systolic pressure and diastolic pressure are usually high. In older people with high blood pressure, systolic pressure is often high (more than 140 mm Hg) while diastolic pressure remains in the normal range (less than 90 mm Hg). This disorder, called isolated systolic hypertension, may have even greater risks than when both systolic pressure and diastolic pressure are high.

A person's blood pressure is determined partly by how well the heart, arteries, and kidneys are working together. The drugs used to treat high blood pressure (antihypertensive drugs) lower blood pressure by affecting how these organs function.

For additional detail on this topic, see How the Body Determines and Controls Blood Pressure.

Causes

The two main types of high blood pressure are essential (or primary) hypertension and secondary hypertension.

Essential hypertension—when the cause is unknown—is by far the most common type. Changes due to aging may contribute. As people age, large arteries gradually stiffen and small arteries may become partially blocked. Also, blood pressure tends to increase. Putting two and two together, some experts conclude that the stiffening of larger arteries and blockages in small arteries partly explain why blood pressure tends to increase as people age. An unhealthy diet (for example, too much salt or alcohol) and chronic stress may also contribute to high blood pressure. Obesity and changes in the way the kidneys function play an important role in the development of high blood pressure. In many nonindustrialized countries, blood pressure is less likely to increase as people age. This difference may be explained by differences in diet and stress, among other things.

Secondary hypertension, which is relatively rare, results from several disorders. Examples are disorders that partially block the arteries to the kidneys (such as atherosclerosis) and disorders that damage the kidneys (such as infections or diabetes). A tumor in the adrenal glands (located on top of the kidneys) or sleep apnea may cause secondary hypertension.

Secondary hypertension can result from using certain drugs. They include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, and nonprescription allergy drugs and cold remedies that contain phenylephrine or pseudoephedrine.

Symptoms

People with high blood pressure may have no symptoms. They may blame high blood pressure for headaches, nosebleeds, or ringing in the ears. But these symptoms may occur whether blood pressure is high or not. Some people with high blood pressure sometimes feel flushed or just do not feel right.

Occasionally, the first symptoms develop because high blood pressure has damaged one or more organs (particularly the brain, heart, or kidneys). Organ damage and symptoms are more likely if high blood pressure is not treated or not adequately treated.

Very high blood pressure sometimes causes sudden headache with loss of sensation in and paralysis of one half of the body. These symptoms result from rupture of an artery in the brain (hemorrhagic stroke).

Chest pain due to coronary artery disease may occur. If heart failure develops, the legs and feet may swell and people may become short of breath during physical activity and eventually during rest. If the kidneys are damaged, people may urinate frequently. If damage is severe, they may feel nauseated and tired.

Vision may become blurred when blood pressure is very high. Arteries in the eyes can be damaged. If one of these arteries ruptures, a blind spot in vision may develop.

Diagnosis

In most people, the only way to diagnose high blood pressure is to measure blood pressure—a simple, painless procedure. To measure blood pressure, a health care practitioner places an inflatable cuff around the person's arm just above the elbow. The person's arm is supported (for example, by a table or desk) and kept at about the same level as the heart. The cuff is connected to a device that measures pressure (called a sphygmomanometer). The practitioner tucks a stethoscope just under the edge of the cuff to be ready to listen. The cuff is inflated until it squeezes (compresses) the main artery in the upper arm (brachial artery) so that blood flow is temporarily stopped. Then the air in the cuff is slowly and steadily released. The practitioner notes pressure on the sphygmomanometer twice: (1) when blood first begins to flow through the artery and the sounds of the heartbeat can be heard (systolic pressure) and (2) when blood flow becomes continuous and heartbeat sounds cannot be heard (diastolic pressure).

Typically, measurements are taken on at least two or three occasions to confirm that blood pressure is consistently high. Ideally, blood pressure is measured in both arms at least the first time, because there may be a difference. The measurement from the arm with the higher reading is usually used to determine whether treatment is necessary. Measurements are made while the person is sitting, usually after several minutes of rest.

A device that can be used to measure blood pressure at home may be recommended. It enables people to check their blood pressure at different times of the day or night. However, taking blood pressure measurements at home is meant to supplement, not replace, having measurements taken by a health care practitioner. Measurements taken at home show what happens to a person's blood pressure under a variety of conditions. Thus, they provide information that may help the doctor determine how to best treat the person.

Some home blood pressure-measuring devices are digital and do not require use of a stethoscope. They measure blood pressure automatically, and the results are displayed on a screen. Digital devices can be especially helpful for people who live alone or who have hearing problems.

Most devices used to monitor blood pressure at home are accurate. However, measurements made at a finger or wrist may not be reliable.

Sometimes blood pressure is high when measured by a doctor or other health care practitioner but is normal when measured at home or somewhere other than a doctor's office. This phenomenon is called white-coat hypertension: The person is reacting to the doctor's white coat. The stress of being in a doctor's office causes blood pressure to be high temporarily. White-coat hypertension, once considered to be of little medical significance, should not be ignored. Higher blood pressure during a visit with a doctor may mean that blood pressure also increases during other stressful situations. If blood pressure is consistently higher than 140/90 mm Hg in a doctor's office despite being lower at home, the doctor occasionally recommends blood pressure monitoring during the person's normal daily activities (home blood pressure measuring).

Ambulatory monitoring involves wearing a cuff that automatically inflates and deflates every 15 to 20 minutes and a small device that records the readings. Ambulatory monitoring is usually done for 24 or 48 hours. It provides measurements that may be more reliable and accurate than isolated measurements taken in a doctor's office. Undergoing ambulatory monitoring is more expensive than using home blood pressure-measuring devices.

In people who have unusually stiff arteries, the inflated blood pressure cuff may not adequately compress the artery. Thus, measurements are sometimes higher than actual blood pressure (a condition called pseudohypertension). In such cases, blood pressure may be normal, or it may be high but not as high as the measurement indicates. In a few people with pseudohypertension, taking drugs to lower blood pressure (antihypertensive drugs) makes blood pressure fall too low. As a result, they may feel lightheaded.

To determine whether another disorder is causing high blood pressure, doctors ask questions about symptoms. For example, doctors may ask about snoring and daytime sleepiness to determine whether sleep apnea could be the cause. A physical examination and simple laboratory tests can also help identify a cause. Typically, tests include analysis of urine (urinalysis) and some blood tests. Other tests, most commonly electrocardiography, may be done to determine whether the heart has been damaged by high blood pressure. Occasionally, more tests, such as echocardiography or exercise stress testing, are necessary.

Treatment

Changes in lifestyle may help lower blood pressure. For example, people should maintain a desirable body weight and exercise regularly. Drinking no more than two alcoholic beverages (10 ounces of wine, 24 ounces of beer, or 2 ounces of whiskey) a day and limiting intake of salt may help. People can learn to manage stress better. Changes in lifestyle also help when antihypertensive drugs are needed, because lower doses may be used.

If high blood pressure is caused by another disorder, treating that disorder may lower blood pressure. If a drug is causing high blood pressure, discontinuing the drug may help.

If these measures do not lower blood pressure enough, antihypertensive drugs are needed. More than three fourths of people with high blood pressure have to take antihypertensive drugs.

Several types of antihypertensive drugs are available. When selecting the most appropriate drug, doctors consider how severe the high blood pressure is, whether other risk factors for heart attacks (such as diabetes or abnormal cholesterol levels) are present, and whether the heart is damaged. They also consider side effects that may occur. For older people, taking antihypertensive drugs can make blood pressure fall too low in certain situations—for example, when they stand up (a disorder called orthostatic hypotension). As a result, they may feel light-headed. Many antihypertensive drugs are effective and relatively free of side effects. Many people need to take more than one type.

Thiazide diuretics (such as hydrochlorothiazide) are often given first. Diuretics increase the amount of salt and water excreted by the kidneys and may expand (dilate) blood vessels. Beta-blockers are sometimes given first. They slow the heart rate and reduce the force of the heart's contractions. Diuretics and beta-blockers reduce the risk of heart attacks, heart failure, strokes, and kidney failure.

Other types of antihypertensive drugs may be used. Each type dilates arteries but may do so in different ways. Alpha-blockers interfere with the action of a hormone called norepinephrine, which causes arteries to contract (constrict). Alpha-beta-blockers combine the actions of beta-blockers and alpha-blockers. Angiotensin-converting enzyme (ACE) inhibitors interfere with the formation of a hormone called angiotensin, which causes arteries to constrict. Angiotensin II receptor blockers interfere with the action of angiotensin. Calcium channel blockers block calcium from entering cells. As a result, arteries dilate and blood pressure is reduced. Some of these drugs also reduce the force of the heart's contractions.

Some people have conditions that make a certain type of antihypertensive drug particularly well suited for them. For example, obese people may respond particularly well to a diuretic or calcium channel blocker. For people with high blood pressure plus diabetes or heart failure, an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin II receptor blocker is recommended because these drugs help protect the kidneys. For people who have had a heart attack or who have angina, migraine headaches, or glaucoma, a beta-blocker is recommended. For men with an enlarged prostate (benign prostatic hyperplasia), an alpha-blocker or alpha-beta-blocker is particularly useful. Alpha-blockers and alpha-beta-blockers relax muscles in the bladder and urethra. Then urine can flow more easily. However, in older people, taking an alpha-blocker or alpha-beta-blocker may cause light-headedness and urinary incontinence.

In general, the goal of treatment is to lower blood pressure below 140/90 mm Hg or even lower in people with diabetes or a kidney disorder. However, in older people, meeting this goal is not always possible. For example, the number of drugs or the dose of drugs needed to decrease blood pressure below 140/90 mm Hg may cause annoying side effects. But any decrease in blood pressure is better than none.

Outlook

Most people with high blood pressure have to take antihypertensive drugs for the rest of their life. If treatment is discontinued, blood pressure is likely to go back up, although it may stay down for the first several months. Sometimes doctors try reducing the dose. If blood pressure increases, the dose is increased again.

If people are concerned about side effects or if they are taking several drugs, they can ask their doctor about reducing the dose or changing the drug. As long as treatment is adequate, people can expect to lead a long life with few restrictions.

See the table Drugs Used for High Blood Pressure.