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Blood pressure (high)

Hypertension is persistent abnormally high blood pressure. Blood pressure is the pressure of blood in your arteries.

The blood circulation is a closed system in which the pressure varies constantly. It rises to a peak, called the systolic pressure, at the height of the contraction of each heartbeat as the heart pumps blood out. Then it falls to a lower level, called the diastolic pressure, which it reaches just before each heartbeat. The diastolic pressure is the running pressure between beats.

In addition to the variations within the cycle, blood pressure varies constantly with the level of physical exertion, with anxiety, stress, emotional changes, and other factors. So single measurements are not particularly meaningful and the blood pressure should be checked under resting conditions, at different times. Blood pressure is measured in terms of millimetres of mercury (mmHg). Hypertension is usually defined as a sustained systolic blood pressure of 140 mmHg or more, or diastolic blood pressure of 90 mmHg or more, at rest.

Lifestyle changes, such as dietary control and increased exercise are important for everyone with raised blood pressure.

Drug treatment is usually recommended in cases of sustained systolic pressure of 160 mmHg or more and/or diastolic pressure 100 mmHg or more.

When blood pressure is between 140/90-160/100mmHg tablets may not be necessary providing that the lifestyle changes work and there are no risk factors for heart disease and stroke, such as high cholesterol, smoking or a previous stroke or heart attack.

Diastolic pressures of 90–109 mmHg are found in about 20 per cent of the middle-aged adult population. They are less common in younger people and more common in those who are older. Diastolic pressures of 110–129 mmHg are found in about 4% of the adult population. However, it is believed that there are large numbers of people who have high blood pressure but are not aware of it.

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