High blood pressure or hypertension is common, with about 40% of adults in England having the condition. There are two measurements used to assess blood pressure:
Systolic pressure is the blood pressure that is exerted when the heart beats and forces blood around the body.
Diastolic pressure is the measure of blood pressure when the heart is resting between beats.
Blood pressure is defined as the amount of pressure exerted on the walls of the arteries as the blood moves through them. It is measured in millimetres of mercury (mmHg).
There is a natural tendency for blood pressure to rise with age, because of the reduced elasticity of the arterial system.
Both the systolic and diastolic pressures are measured, and these figures are usually represented with the systolic pressure first, followed by the diastolic pressure, e.g. 120 over 80 means a systolic pressure of 120mmHg and a diastolic pressure of 80mmHg.
High blood pressure is a blood pressure that is 140/90 mmHg or above each time it is taken.
For the majority of people with high blood pressure, the cause is unknown, and this is called 'primary hypertension' or 'essential hypertension'. For the remainder, there will be an underlying cause, and this is called 'secondary hypertension'. Some of the main causes for secondary hypertension are:
- chronic kidney disease
- diseases in the arteries supplying the kidneys
- chronic alcohol abuse
- hormonal disturbances
- endocrine tumours
High blood pressure often causes no symptoms or immediate problems, but it is a major risk factor for developing a serious cardiovascular disease (conditions that can affect the circulation of blood around the body), such as a stroke or heart disease, as your heart has to work harder to pump blood around your body. Over time, this can weaken it.
Complications which can be caused by high blood pressure therefore include:
- narrowing of the arteries
stroke (haemorrhage or blood clot in the brain)
aneurysm (dangerous expansion of an artery which becomes weakened and may rupture)
- heart failure
- kidney failure
- eye damage
Also, the increased pressure can damage the walls of your arteries, which can result in a blockage or cause the artery to split (haemorrhage). Both of these situations can cause a stroke.
Certain factors can seriously aggravate hypertension and increase the risk of complications:
- a family history of high blood pressure
obesity or a high body mass index
- kidney disease
- high alcohol consumption
excessive salt intake
lack of exercise
certain medicines, such as steroids
A one-off blood pressure reading that is high does not mean that you have 'high blood pressure'. Your blood pressure varies throughout the day. It may be high for a short time if you are anxious, stressed, or have just been exercising.
In addition, some people have 'white coat' hypertension, or “white coat syndrome”, which is a phenomenon in which patients exhibit elevated blood pressure in a clinical setting but not in other settings. It is believed that this is due to the anxiety some people experience during a visit to the doctor or nurse.