High Blood Pressure: introduction
High blood pressure increases the risk of disease and death in the population. As a clinical risk factor, it is of major public health importance (Lawes et al, 2004).
Blood is circulated through the body by the heart, and the beating of the heart leads to peaks and troughs in blood pressure. The peaks are called systolic and the troughs diastolic. Blood pressure is measured as systolic/diastolic, e.g. 140/90 mmHg (pressure equivalent of millimetres of mercury).
Blood pressure varies normally from minute to minute, and over days and weeks, but a consistently raised blood pressure increases the risk of certain diseases. Any definition of high blood pressure is somewhat arbitrary, but there is consensus within the UK that 140/90 mmHg is appropriate as the upper limit for normal blood pressure (Maryon-Davis and Press, 2005).
The measurement of blood pressure is an important consideration because it requires a certain level of skill, an appropriate setting and well maintained and calibrated equipment. A measurement should be based on at least two readings (see British Hypertension Society measurement guidelines).
High blood pressure increases the risk of a range of diseases:
- coronary heart disease (angina, heart attack)
- stroke (both that due to a blood clot and that due to bleeding)
- heart failure (heart strain - especially left ventricular)
- aortic aneurysm (dilated aorta with risk of massive internal haemorrhage)
- peripheral vascular disease (clogged blood supply to the limbs)
- chronic kidney disease (including established renal failure)
- retinal disease (visual impairment)
The total cost of high blood pressure in the UK has been estimated at over £7 billion (Maryon-Davis and Press, 2005).