High Blood Pressure

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Blood pressure is the amount of force your blood exerts against the walls of your arteries. Normal blood pressure effectively and harmlessly pushes the blood from your heart to your body's organs and muscles so they can receive the oxygen and nutrients they need.

Blood pressure is variable—it rises and falls during the day. When blood pressure stays elevated over time, however, it is called high blood pressure or hypertension.

According to the most recent estimates, about 73 million Americans age 20 and older have hypertension and nearly half are women, according to the American Heart Association. High blood pressure killed nearly 54,707 Americans in 2004 and was listed as a primary or contributing factor in 300,000 deaths.

Hypertension can occur in both children and adults, but it is more common in adults, particularly African Americans and the elderly. People with other conditions such as diabetes and kidney disease are likely to become hypertensive. In addition, being overweight, drinking alcohol excessively (defined as more than two drinks a day for men and one drink a day for women), and taking oral contraceptives may increase blood pressure. Overall, nearly one in three American adults has hypertension.

About half of the 73 million Americans with high blood pressure are women. More men than women have hypertension, until women reach menopause, when their risk becomes greater than men's. An estimated 27 percent of women have high blood pressure.

Blood pressure is typically expressed as two numbers, one over the other, and is measured in millimeters of mercury (noted as mm Hg). The first number is the systolic blood pressure, the pressure used when the heart beats. The second number, diastolic blood pressure, is the pressure that exists in the arteries between heartbeats.

Depending on your activities, your blood pressure may increase or decrease throughout the day. If you are not acutely ill, are over 18 years of age and are not taking antihypertensive drugs, a blood pressure reading of 119 mm Hg or below systolic and/or 79 mm Hg or below diastolic (119/79) is considered normal.

If your systolic blood pressure is 120 to 139 mm Hg systolic and/or your diastolic pressure is 80 to 89 mm Hg, you have prehypertension. This means that you don't have high blood pressure now but are more likely to develop it in the future, and you have increased risk factors for cardiovascular disease and other conditions related to hypertension.

A blood pressure level of 140/90 mm Hg or higher is considered high.

You have stage 1 hypertension if your systolic pressure is 140 to 159 and/or diastolic is between 90 and 99. If your systolic pressure is 160 or above and/or your diastolic is 100 or more, you have stage 2 hypertension. Only one of the numbers needs to be above normal for a diagnosis of high blood pressure; that is, you can have isolated systolic or diastolic hypertension. Isolated systolic hypertension (ISH) is the most common form of high blood pressure in older Americans. The National Heart, Lung, and Blood Institute (NHLBI) estimates that 65 percent of people with hypertension over age 60 have ISH.

The cause of approximately 90 to 95 percent of all hypertension isn't known. This type of hypertension is called primary or essential high blood pressure. Secondary hypertension is somewhat different because it represents all of the specific diseases that cause elevated blood pressure. It is important to diagnose this type of hypertension because the treatment differs from primary hypertension. While there is no cure for primary hypertension, it is easily detected and is usually controllable.

Still, nearly one-third of those who suffer from high blood pressure don't know they have it, and people can have high blood pressure for years without knowing they have it. That's why high blood pressure has been called "the silent killer."

Of those with hypertension, only 34 percent have the problem under control, defined as a level below 140/90 mm/Hg. Left untreated, hypertension can result in permanent damage to the small blood vessels of the body, which can damage vital organs and increase the risk of heart attack and stroke. It can also cause acute or chronic circulatory problems.

Of those with hypertension, only 35 percent have the problem under control, defined as a level below 140/90 mm Hg. Left untreated, hypertension can result in permanent damage to the small blood vessels of the body, which can damage organs such as the heart, brain and kidneys, leading to heart attacks, stroke and kidney failure. It can also cause acute or chronic circulatory problems. Elevated blood pressure levels significantly increase your risk for coronary heart disease. According to the American Heart Association, a 40-year-old woman with a normal body mass with high blood pressure has more than three times the risk of dying from a heart attack, almost four times the risk of dying from a stroke, three times the risk of developing heart failure and three times the risk of developing kidney disease as a woman with normal blood pressure. Consistent high blood pressure also increases your risk for congestive heart failure and can lead to other problems such as:

• Atherosclerosis: Plaque collects on the walls of hypertension-damaged blood vessels, which can eventually lead to blockages that may result in a stroke or heart attack. Although this plaque builds up for many reasons as you age, high blood pressure hastens the process.

• Eye damage: High pressure in blood vessels can cause tiny hemorrhages in the retina, the light-sensitive membrane in the back of your eye on which images are formed. If this happens, you may lose some of your vision.

• Heart enlargement or failure: There are two types of heart failure. In the first, the walls of the heart are weak and thin as a result of being stretched by increasing amounts of pooling blood in the heart. In the second, commonly seen in people with hypertension, the heart muscle enlarges in response to the higher pressure and increased workload. It becomes so big it begins to close off the ventricular chamber, decreasing the amount of blood that can fill the heart. This is called diastolic dysfunction, because the heart muscle can't relax normally and allow blood to fill the chamber.

• Kidney damage and failure: Hypertension causes arteries going to your kidneys to become constricted, making them less efficient at filtering waste from your body. About 25 percent of people who require kidney dialysis have kidney failure due to hypertension. This is especially true in African Americans. Early treatment of hypertension can help prevent kidney damage.

You should have your blood pressure checked whenever you see a health care professional. Because blood pressure can be variable, it should be checked on several different days before a high blood pressure diagnosis is made. One elevated blood pressure reading doesn't necessarily mean you have high blood pressure, but it does warrant repeated measurements and means you have to watch your blood pressure carefully.

Dietary and lifestyle changes may help you control high blood pressure. If you have mild hypertension, you may be able to lower your blood pressure by reducing the amount of sodium (salt) in your diet, reducing fat intake, eating a diet high in fruits, vegetables and low-fat dairy (the DASH diet) and reducing alcohol consumption. If you are overweight, losing weight may reduce your blood pressure. Increasing your physical activity, even if you don't lose weight, can also reduce blood pressure.

For some people, lifestyle changes aren't enough to lower blood pressure. Luckily, high blood pressure can be treated very successfully with long-term medication.

Commonly prescribed drugs include diuretics, beta blockers, angiotensin-converting enzyme inhibitors (ACE inhibitors), angiotensin II receptor blockers (ARBs), direct renin inhibitors (DRIs), calcium channel blockers (CCBs), vasodilators, alpha-beta blockers, central-acting agents and alpha blockers. Because there is no cure for most hypertension cases, treatment generally must be carried out for life to prevent blood pressure from rising again.

Many of these drugs are also available to treat isolated systolic hypertension (ISH) to reduce your risk of coronary heart disease and stroke.

Causes of Hypertension

The 90 to 95 percent of hypertension cases in which the cause can't be determined are called essential or primary hypertension cases. Hypertension may also be a symptom of an identified problem (see below) that generally corrects itself when the identified cause is corrected. This type of high blood pressure is called secondary hypertension.

Possible causes of secondary hypertension include:

• Renal artery stenosis (narrowing of the arteries leading to your kidneys)

• Adrenal gland disease (Cushing's disease) or adrenal tumors

• Kidney disease

• Preeclampsia (hypertension and increased urine protein levels sometimes caused by pregnancy)

• Thyroid disease

• A large intake of licorice root extract (equivalent to 25 to 40 licorice candies a day for several years)

Other factors affecting blood pressure include:

• Use of birth control pills

• Psychologic stress

• Severe pain

• Drug or alcohol withdrawal

• Use of amphetamines, cocaine or other stimulants

• Use of steroids

• Overuse of nicotine nasal sprays, gum, patches and lozenges designed to help smokers kick the habit

• Sleep apnea

Your health care professional should monitor your blood pressure if you are taking oral contraceptives. Your blood pressure should also be carefully monitored if you're pregnant, because some women develop preeclampsia-related hypertension during pregnancy. One of the leading causes of maternal death, preeclampsia is hypertension combined with protein in the urine and/or swollen hands and feet. It typically occurs after the 20th week of pregnancy. It can lead to premature and low-birth-weight babies.