Persistent high blood pressure that may damage the arteries and the heart
- More common with increasing age
- Slightly more common in males
- Often runs in families; more common in black people
- Stress, alcohol abuse, a high-salt diet, and excess weight are risk factors
In the UK, an estimated 30–40 per cent of adults have 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 such as heart attacks (see Myocardial infarction), coronary artery disease, and stroke will develop.
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 millimetres of mercury (mmHg). The blood pressure of a resting, healthy young adult should not 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 blurred vision. However, usually 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 recent years, health education and screening programmes have led to many more people being diagnosed with hypertension at an early stage before symptoms occur. Early diagnosis together with improved treatments have 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. It is also marginally more common in men. People who are overweight or who drink excessive amounts of alcohol are more likely to develop hypertension, and a stressful lifestyle may aggravate the condition. Although hypertension occurs most often in developed countries, it is now a significant problem in the developing world too. The tendency to develop hypertension is thought to be inherited, and black people are more susceptible to the condition. The condition is rare in countries where people typically have a low-salt diet, suggesting that salt may be a contributing factor.
In a minority of cases, an underlying cause is found, such as kidney disease or the hormonal disorders hyperaldosteronism, Cushing’s syndrome, or phaeochromocytoma. Some drugs, such as combined oral contraceptives and corticosteroids, can cause hypertension.
When hypertension develops during pregnancy, it can lead to the development of the potentially life-threatening conditions pre-eclampsia and eclampsia. Although the elevated blood pressure usually returns to normal after the birth, women who have hypertension in pregnancy are at a slightly increased risk of developing it later in life.
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 with high blood pressure who also 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 supplying the retina in the eye may also be damaged by hypertension (see Retinopathy).
How is it diagnosed?
It is important that you have your blood pressure measured every 3–5 years from about the age of 20, or more frequently if you already have high blood pressure or a condition such as diabetes mellitus (see Blood pressure measurement). 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 people become anxious when visiting their doctor, which may cause a temporary rise in blood pressure; this phenomenon is known as “white coat hypertension”. Consequently, a diagnosis of hypertension is usually not made unless you have elevated blood pressure on three separate occasions. If your readings are variable, you may be offered a portable device to measure your blood pressure 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 (see ECG). Your eyes may be examined to look for damaged blood vessels. You may also have tests to look for other factors, such as a high blood cholesterol level, that may increase your risk of a heart attack.
If you are young or have severe hypertension, you may have tests to find the underlying cause. For example, you may have urine and blood tests and ultrasound scanning 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 (see Are you a healthy weight?). 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 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, consult your doctor so that your medication can be adjusted. He or she may recommend that you measure your blood pressure regularly yourself to help evaluate your treatment. You can now buy small electronic blood pressure machines for use at home, but seek advice from your doctor first.
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.
What is the prognosis?
The outlook depends on how high your blood pressure is and how long it has been high. For most people, lifestyle changes and drug treatment can control blood pressure and reduce the risk of complications from hypertension. These measures usually need to be maintained for life. Long-standing, severe hypertension carries the greatest risk of complications.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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