Hypertension Dr Rob Hicks In the UK, about 16 million people - that's more than one in four - have high blood pressure.

In this article

What is hypertension? Symptoms

Causes and risk factors Treatment and recovery

Hypertension refers to high blood pressure.

Blood pressure is the force exerted by blood on the walls of the arteries when the heart beats. When measured, two readings are recorded.

The first is called the systolic pressure and represents the force of the blood as the heart contracts (beats) to pump it around the body. This is the higher of the two readings.

The second, called the diastolic, is the pressure while the heart is relaxed and filling with blood again in preparation for the next contraction or heart beat. This value is lower than the systolic pressure.

Blood pressure changes throughout the day. In particular, it increases during exercise and decreases during sleep.

What is considered to be an acceptable blood pressure and what is hypertension (and then what needs treatment) depends on several factors. A single high reading is not enough to warrant a diagnosis of hypertension as blood pressure can be raised in all of us now and then – even the sight of a doctor can be enough to put it up. So there must be at least two high readings to cause concern.

Hypertension is then diagnosed when either or both of the systolic and diastolic pressures are persistently raised above 140(systolic) / 90(diastolic) mmHg. Hypertension therefore may just be a high systolic pressure (this is known as isolated systolic hypertension), just a high diastolic, or both.

Although high blood pressure can cause headaches, dizziness and problems with vision, the majority of people suffer no symptoms at all. As a result many people with hypertension remain undiagnosed because they have no symptoms to motivate them to see a doctor or get their blood pressure checked.

However, despite the lack of symptoms hypertension can lead to heart attack, stroke, kidney damage, and many other medical problems which is why it's important for people to have their blood pressure checked regularly so it can be diagnosed and treated.

In 90-95 per cent of cases there's no specific cause that can be found for the raised blood pressure. This is known as essential hypertension and it is probably due to a variety of factors. It does tend to run in families, and genetics may play a part.

In around 5-10 per cent of cases, kidney disease, endocrine disease (for example, underactive thyroid) and drugs (such as the contraceptive pill) are found to be responsible. This is sometimes called secondary hypertension. For example, narrowing of the artery to the kidney, known as renal artery stenosis, accounts for approximately 1% of mild to moderate cases of high blood pressure and as many as 10% of cases of severe or difficult to treat hypertension.

If your blood pressure is normal then it needs to stay that way. If it's high, it needs to be brought down to a normal level, and the aim is usually to get blood pressure down to below 140/90 mmHg.

When high blood pressure is first diagnosed, tests may be done for an underlying cause (i.e. secondary hypertension) especially if the person is young or has very high blood pressure. If an underlying cause is found it should be treated.

There's no cure as such for essential hypertension, but following a healthy lifestyle can be enough to bring blood pressure down to a normal level. This is one reason why drug treatment may not be offered for healthy individuals with only mild hypertension (above 140/90 mmHg but below 160/100 mmHg).

Medication is used if lifestyle changes alone fail to lower blood pressure sufficiently.

Its generally recommend that drug treatment is offered to :

• those with a blood pressure above 160/100 mmHg
• those with isolated systolic hypertension of more than 160 mmHg
• those with a blood pressure of more than 140/90 mmHg (i.e mild hypertension) but who also have cardiovascular disease or significant risk of developing cardiovascular disease, diabetes, or damage to the heart, kidney or eyes as a result of high blood pressure.

Current UK guidelines also recommend that blood pressure levels need to be even lower for certain people and say treatment should aim to lower blood pressure to below 130/80 if a person has :

• a complication of diabetes, especially kidney problems
• had a serious cardiovascular event such as a heart attack, TIA or stroke
• has certain chronic kidney diseases

All medicines can have side effects and sometimes it is necessary to try different drugs if initial treatments cause problems.

This article was last medically reviewed by Dr Trisha Macnair in March 2009.