What is blood pressure?
Blood pressure is the pressure of blood in your blood vessels (arteries), measured in millimetres of mercury (mm Hg). Your blood pressure is recorded as two figures - for example, 150/95 mm Hg. You may hear this said as '150 over 95'.
- The top (first) number is the systolic pressure. This is the pressure in the arteries when the heart contracts.
- The bottom (second) number is the diastolic pressure. This is the pressure in the arteries when the heart rests between each heartbeat.
Up until the age of 65 years it is more common in men than in women. However, after the age of 65 years it is more common in women. As the population as a whole is living longer, high blood pressure is becoming more common.
High blood pressure is uncommon under the age of 40 years. Between the ages of 45-54 years, about a third of men and a quarter of women have high blood pressure. Over the age of 75 years, about two thirds of men and more than three quarters of women have high blood pressure.
What causes high blood pressure?
The cause of high blood pressure (hypertension) is not known in most cases
This is called essential hypertension. The pressure in the blood vessels (arteries) depends on how hard the heart pumps and on how much resistance there is in the arteries. It is thought that slight narrowing of the arteries increases the resistance to blood flow, which increases the blood pressure. The cause of the slight narrowing of the arteries is not clear. Various factors probably contribute.
In some cases, high blood pressure is caused by other conditions
It is then called secondary hypertension. For example, certain kidney or hormone problems can cause high blood pressure. In some cases, medication taken for other conditions can cause blood pressure to rise.
Risk factors for high blood pressure
High blood pressure is more common in people:
- With diabetes. This is the case in both type 1 and type 2 diabetes. However, it is even more common in those with type 2 diabetes.
- From African-Caribbean origin.
- From the Indian subcontinent.
- With a family history of high blood pressure.
- With certain lifestyle factors. That is, those who:
- Are overweight.
- Eat a lot of salt.
- Don't take enough exercise.
- Drink a lot of alcohol.
- Have a lot of stress.
Further reading and references
Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults; Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, 2017
Hypertension: management of hypertension in adults in primary care; NICE Clinical Guideline (August 2011)
Guidelines for the management of arterial hypertension; ESH/ESC Clinical Practice Guidelines, European Society of Cardiology (2013)
He FJ, Li J, Macgregor GA; Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. 2013 Apr 3346:f1325. doi: 10.1136/bmj.f1325.
Description of the DASH (Dietary Approaches to Stop Hypertension) Eating Plan; National Institutes of Health
Ettehad D, Emdin CA, Kiran A, et al; Blood pressure lowering for prevention of cardiovascular disease and death: a systematic review and meta-analysis. Lancet. 2016 Mar 5387(10022):957-67. doi: 10.1016/S0140-6736(15)01225-8. Epub 2015 Dec 24.
Alcohol Guidelines Review – Report from the Guidelines development group to the UK Chief Medical Officers; Department of Health, January 2016
2016 European Guidelines on cardiovascular disease prevention in clinical practice; European Society of Cardiology (2016)
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