In the US, about 1 in 5 adults has persistent high blood pressure, also known as hypertension. The condition puts strain on the heart and arteries, resulting in damage to delicate tissues. If it is left untreated, hypertension may eventually affect the eyes and kidneys. The higher the blood pressure, the greater the risk that complications will develop such as heart attack, coronary artery disease and stroke.

Blood pressure varies naturally with activity, rising during exercise or stress and falling during rest. It also varies among individuals, gradually increasing with age and weight. Blood pressure is expressed as two values given in units of millimeters of mercury (mmHg). The blood pressure of a resting, healthy young adult should no be more than 120/80 mmHg. In general, a person is considered to have hypertension when his or her blood pressure is persistently higher than 140/90 mmHg, even at rest.

Hypertension does not usually cause symptoms, but, if your blood pressure is very high, you may have headaches, dizziness, or blurry vision. However, in most cases, the only symptoms that develop are those due to the damage caused by hypertension. By the time these arise and hypertension becomes evident, irreversible damage to arteries and organs has occurred. Hypertension is sometimes called the "silent killer" because individuals may have a fatal stroke or heart attack without warning.

In the last 20 years, health education and screening programs have led to many more people being diagnosed with hypertension at an early stage before symptoms occur. Early diagnosis, together with improved treatments, has substantially reduced the incidence of heart attacks and strokes.

What are the causes?
In about 9 in 10 people with hypertension, there is no obvious cause for the condition. However, both lifestyle and genetic factors may contribute. The condition is most common in middle aged and elderly people because the arteries become more rigid with age. High blood pressure is also more common among men. People who are overweight or drink large amounts of alcohol are more likely to develop hypertension, and a stressful lifestyle may aggravate the condition. Hypertension therefore occurs most often in developed countries. The condition is rare in countries that have a low-salt diet, suggesting that salt may be a contributing factor. A tendency to develop hypertension may be inherited, and the condition is more common among African-American people.

In a minority of cases, an underlying cause of the hypertension is identified, such as kidney disease or a hormonal disorder, such as hyperaldosteronism or Cushing syndrome. Some drugs, such as combined oral contraceptives and corticosteroids, can cause hypertension.

In pregnant women, hypertension can lead to the development of the potentially life-threatening conditions preeclampsia and eclampsia. The elevated blood pressure usually returns to normal after the birth.

ARE THERE COMPLICATIONS?
The risk of damage to the arteries, heart, and kidneys rises with the severity of hypertension and the length of time for which it is present. Arteries that have been damaged are at greater risk of becoming narrowed by atherosclerosis in which fatty deposits build up in vessel walls, causing them to narrow and restricting blood flow.

Atherosclerosis is more likely in people who smoke or who have high blood cholesterol levels. Atherosclerosis of the coronary arteries may lead eventually to chest pain (see angina) or to a heart attack. In other arteries in the body, atherosclerosis may result in disorders such as aortic aneurysm or stroke. Hypertension puts strain on the heart that may eventually lead to chronic heart failure.

Damage to the arteries in the kidneys may result in chronic kidney failure. The arteries in the retina in the eye may also be damaged by hypertension.

HOW IS IT DIAGNOSED?
It is important that you have your blood pressure measured routinely at least every 2 years after age 18. If your blood pressure is more than 140/90 mmHg, your doctor may ask you to return in a few weeks so that he or she can check it again. Some individuals become anxious when visiting their doctor, which may cause a temporary rise in blood pressure. Therefore, a diagnosis of hypertension is usually not made unless you have elevated blood pressure on three separate occasions. If your readings are variable, your doctor may arrange for you to have a portable device so that you can measure your blood pressure regularly at home.
If you have hypertension, your doctor may arrange for tests that check for organ damage. Tests for heart damage include echocardiography or electrocardiography. Your eyes may be examined to look for damaged blood vessels. You may also have tests to look for other/actors, such as a high blood cholesterol level, that may increase your risk of a heart attack.
If you are young or have severe hypertension, your doctor may recommend tests to identify the underlying cause. For example, urine and blood tests and ultrasound scanning may be arranged to look for kidney disease or a hormonal disorder.

What is the treatment?
Hypertension cannot usually be cured but can be controlled with treatment. If you have mild hypertension, changing your lifestyle is often the most effective way of lowering your blood pressure. You should reduce your salt and alcohol consumption and try to keep your weight within the ideal range . If you smoke, you should give up.

If self-help measures are not effective in reducing your blood pressure, your doctor may prescribe antihypertensive drugs. These drugs work in different ways, and you may be prescribed just one type of drug or a combination of several. The type of drug and the dosage are tailored to the individual, and it may take some time to find the right combination and dosage. If you develop side effects from drug treatment, you should consult your doctor so that the medication can be adjusted.

Some doctors recommend that you regularly measure your blood pressure yourself. Self-monitoring helps your doctor evaluate your drug treatment.

If your hypertension has an obvious underlying medical cause, such as a hormonal disorder, treatment of this disorder may result in your blood pressure returning to a normal level.