High blood pressure (hypertension) is a sustained elevation of blood pressure greater than 140/90 mm Hg. With hypertension, the pressure within the arteries of the body is too high and causes damage to the eyes, kidneys, brain, and heart. The damage can be prevented with proper treatment, consisting of diet, exercise, weight loss, and sometimes medications.
Hypertension affects 50 million Americans (one in four) and 1 billion people worldwide. Of the 50 million Americans with hypertension, 30% do not know they have the disease, and only one fourth sustain adequate blood pressure control (less than 140/90 mm Hg). One reason that people with hypertension may not be aware that they have the disease is that high blood pressure generally has no symptoms unless it is extremely high. For this reason, it is often called the “silent killer.” The first indication of long-standing hypertension may be symptoms of damage already done to the body, such as a stroke or heart attack.
Hypertension increases with age. It is more common among African Americans than whites. As the American population ages and obesity reaches epidemic proportions, the incidence of hypertension is predicted to rise. Obesity is thought to be a major contributing factor to hypertension in children and adolescents, and the incidence of obesity in children has risen sharply in recent years.
Classification Of Hypertension
A blood pressure reading consists of two numbers. The top or higher number, known as the systolic blood pressure, measures the pressure in millimeters of mercury (mm Hg) within the arteries when the heart is pumping or contracting. The bottom number, or diastolic blood pressure, measures the pressure when the heart is at rest. Elevation of either the systolic or the diastolic blood pressure (or both) constitutes hypertension. Elevation of the systolic blood pressure is associated with more complications than elevation of the diastolic blood pressure. Historically, it was believed that an elevated systolic blood pressure was “normal” as individuals grew older and that an increased diastolic blood pressure carried a worse prognosis. However, recent studies have proved this to be false. These studies show that elevation of the systolic blood pressure causes more damage than elevation of the diastolic blood pressure.
Blood pressure readings in any individual vary depending on time of day, psychosocial factors, and degree of physical activity. One elevated reading does not mean that a person has hypertension. Instead, the average of two or more readings made several weeks apart must be elevated in order to confirm the diagnosis.
Individuals with blood pressure readings averaging less than 120/80 mm Hg are considered to be “normal” or “optimal.” Those with blood pressure readings averaging between 120 and 139 for the systolic or 80 and 89 for the diastolic are labeled as prehypertensive because about half of these individuals go on to develop hypertension. Stage 1 hypertension is defined as a systolic blood pressure of 140 to 159 or a diastolic blood pressure of 90 to 99. Stage 2 hypertension is blood pressure averaging greater than or equal to 160/100 mm Hg (for either number or both).
Causes And Risk Factors For Hypertension
In about 95% of all cases of hypertension, no cause can be found. This type of hypertension is known as primary hypertension. In the other 5% of cases, secondary hypertension occurs, in which a specific cause can be established and in many cases treated or corrected. After the treatment of secondary hypertension, the person no longer has the disease. Examples of secondary hypertension include pregnancy-induced hypertension, thyroid disorders, and narrowed arteries leading to the kidneys.
Most affected individuals have primary hypertension. Although no exact cause has been established, certain risk factors have been identified that are associated with the disease. Individuals who possess one or more of these factors have a higher chance of developing hypertension than those who do not. Risk factors for hypertension include age (hypertension increases with age), gender (hypertension occurs more frequently in men younger than age 55 and women older than age 55), family history of hypertension, obesity, race (African Americans and Mexican Americans have increased rates of hypertension), physical inactivity, smoking and other tobacco use, diabetes, and excess alcohol intake (more than two drinks a day for men and one drink a day for women). Experts disagree on the role stress plays in the development of hypertension. Now it is generally believed that it is not the degree of stress, but how one handles stress, that contributes to hypertension. Although some risk factors cannot be changed, many are modifiable, and altering them can decrease the chances of developing hypertension. For example, if an obese individual loses weight, that person may never have an increased blood pressure.
Complications Of Hypertension
If untreated, hypertension can lead to debilitating complications or even death. In general, the higher the blood pressure, the greater the number of complications in the body. The damage usually occurs in four target organs: the brain, eye, heart and blood vessels, and the kidney.
Uncontrolled hypertension is a leading cause of stroke in the United States. Sustained high blood pressure weakens the walls of arteries in the brain causing a rupture of a blood vessel. This rupture causes a cerebral hemorrhage or stroke. Hypertension also causes hard, rough, irregular deposits on the interior of arteries. These rough areas promote the formation of blood clots, which can block the blood supply to certain areas of the brain and cause a stroke.
Tiny blood vessels in the back of the eye (retina) can rupture with uncontrolled hypertension, leading to decreased vision or blindness. Individuals with hypertension should have a dilated eye exam by an ophthalmologist at least once a year to determine whether damage is occurring. Laser treatment can often correct this condition.
Heart and Blood Vessels
Uncontrolled hypertension can lead to a heart attack or heart failure. When the blood vessels become damaged with hardened and rough deposits (called arteriosclerosis), blood flow in the heart and the rest of the body decreases. The heart must pump harder to meet the needs of the body. Eventually, the heart enlarges to try to meet these demands, and it may become exhausted and fail to pump adequately. This condition is called heart failure. Symptoms of heart failure include shortness of breath, cough, and swelling of the legs.
When the blood vessels in the legs are narrowed, the person may experience pain in the leg muscles when walking. The pain may then disappear with rest. Narrowed arteries in the neck vessels promote the formation of clots, which can travel to the brain and cause a stroke.
Hypertension can cause narrowing or rupture of blood vessels in the kidneys. When this happens, the kidneys are unable to filter wastes and kidney failure may result. The person will need dialysis (removal of body wastes by a machine) several times a week or kidney transplantation.
Treatment Of Hypertension
Although hypertension can cause life-threatening damage to the body, treating and controlling hypertension lessens or eliminates complications. The goal of therapy is to reduce death and disability by sustaining a blood pressure less than 140/90 mm Hg. In people with kidney disease or diabetes, the goal blood pressure is less than 130/80 mm Hg.
To attain these goals, the person with hypertension should immediately begin lifestyle modification efforts: consume a diet low in sodium and rich in potassium and calcium, stop using tobacco, exercise 30 minutes a day, and consume moderate amounts of alcohol. Often, lifestyle modifications alone are enough to bring the blood pressure down to the goal. But if they do not, medications may be added. Several types of antihypertensive medicines effectively reduce blood pressure. Medication selection will be based on several factors, including the presence of any other diseases, such as diabetes. Often, a diuretic, a medicine that reduces fluid in the bloodstream, is the first one chosen. Most people require two or more types of drugs to reach the target goal. These medications do not cure hypertension, but they lower the blood pressure so that damage to the body does not occur. Therefore, blood pressure medications must be taken for life.
The evidence for treating hypertension to avoid complications is quite compelling. Why, then, do many individuals remain untreated or undertreated for hypertension? First, they may not know they have the disease. They do not feel ill because there are usually no symptoms of hypertension. Next, people with hypertension may not be able to afford the medications. Many people in the United States lack adequate health insurance and must pay full price for all prescriptions. These can be quite expensive in some cases. Sometimes, blood pressure medications make the person feel weak or dizzy. Because most people do not feel ill to begin with, they see no reason to take a medicine that may make them feel bad. Then, many people fear impotence from taking blood pressure medications. In fact, the incidence of this side effect is extremely low. If it does occur, the category of medicine can be changed to another type less likely to cause problems.
Adequate public education should focus on the dangers of hypertension and the lifestyle modifications to prevent it altogether. Screening programs should target persons of lower socioeconomic status who rarely seek health care because they lack health insurance. These measures are the best preventive health care to avoid damage from this very common disease.
- American Heart Association, http://www.americanheart.org
- American Medical Association. (2004). Family medical guide(4th ed.). Hoboken, NJ: Wiley.
- Chobanian, A. V., Bakris, L., & Black, H. R. (2003). The seventh report of the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report. JAMA, 289,2560–2571.
- Kaplan, M. (Ed.). (2002). Clinical hypertension (8th ed.).New York: Lippincott Williams & Wilkins.
- Litin, C. (Ed.). (2002). Mayo Clinic family health book(3rd ed.). New York: Harper Collins.
- National Heart Lung and Blood Institute. (n.d.). Your guide to lowering high blood pressure. Retrieved from http://www.nhlbi.nih.gov/hbp
- Sharma, (2004). Hypertension. Retrieved from http://www.emedicine.com/med/topic1106.htm
- Tierney, L. M. (Ed.). (2005). Current medical diagnosis and treatment (44th ). New York: McGraw-Hill.
- WebMD, http://www.webmd.com