High blood pressure (hypertension)

Health and Nutrition > Diseases > H Reviewed by Neal Uren, consultant cardiologist and Dr Dan Rutherford,



The heart is a pump designed to force blood through our body. Blood is pumped from the heart through the arteries out to our muscles and organs.

Pumps work by generating pressure. Put simply, too much pressure puts a strain on the arteries and on the heart itself. This can cause an artery to rupture or the heart to fail under the strain - in the worst case stopping altogether.

Blood pressure depends on a combination of two factors:

- how forcefully the heart pumps blood around the body
- how narrowed or relaxed your arteries are.

Hypertension occurs when blood is forced through the arteries at an increased pressure.

Around 10 million people in the UK have high blood pressure - that's one in five of us.

What is normal blood pressure?

Blood pressure is measured using two numbers. An example of this could be 'the blood pressure is 120 over 80', which is written as '120/80mmHg'.

- The first figure is the systolic blood pressure - the maximum pressure in the arteries when the heart contracts (beats) and pushes blood out into the body.
- The second figure is the diastolic blood pressure. This is the minimum pressure in the arteries between beats when the heart relaxes to fill with blood.

Because the height of a mercury column is used in blood pressure gauges, standard blood pressure readings are always written as so many 'millimetres of mercury', which is abbreviated to 'mmHg'.

The systolic pressure is always listed first, then the diastolic pressure. A typical normal blood pressure reading would be 120/80 mmHg.

What's classed as high?

There is a natural tendency for blood pressure to rise with age due to the reduced elasticity of the arterial system. Age is therefore one of the factors that needs to be taken into account in deciding whether a person's blood pressure is too high.

In general terms, people with a systolic blood pressure consistently above 160mmHg and/or a diastolic pressure over 100mmHg need treatment to lower their blood pressure.

People with slightly lower blood pressures (140-159mmHg systolic or 90-99mmHg diastolic) may also need treatment if they have a high risk of developing cardiovascular disease, eg stroke or angina (chest pains).

What are the symptoms?

One of the big problems with high blood pressure is that it hardly ever causes symptoms.

This means it may go unnoticed until it causes one of its later complications such as a stroke or heart attack.

Despite the popularity of such ideas, nosebleeds and ruddy complexions are hardly ever caused by high blood pressure.

Severe hypertension can cause symptoms such as:

- headache
- sleepiness
- confusion
- coma.

What complications are caused by high blood pressure?

- Atherosclerosis: narrowing of the arteries.
- Stroke: haemorrhage or blood clot in the brain.
- Aneurysm: dangerous expansion of the main artery either in the chest or the abdomen, which becomes weakened and may rupture.
- Heart attack.
- Heart failure: reduced pumping ability.
- Kidney failure.
- Eye damage.

What causes hypertension?

For more than 90 per cent of people with high blood pressure, the cause is unknown. This is called 'primary' or 'essential hypertension'.

In the remaining 10 per cent or so, there is an underlying cause. This is called 'secondary hypertension'.

Some of the main causes for secondary hypertension are:

- chronic kidney diseases
- diseases in the arteries supplying the kidneys
- chronic alcohol abuse
- hormonal disturbances
- endocrine tumours.

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