What is high blood pressure?
High blood pressure, or hypertension, increases the risk of heart attacks, strokes, kidney disease and eye damage. It is known as a 'silent' killer as it causes few, if any, symptoms.
What is high blood pressure?
Blood pressure is a measure of the force of your blood pressing against the walls of your larger blood vessels, or arteries, as it is pumped around the body by your heart.
The level of pressure reflects the amount of blood pumped out by the heart and the amount of resistance by the blood vessels to the flow of the blood (which depends how narrow or wide the blood vessels are).
In high blood pressure, also known as hypertension, the heart must work harder than normal to circulate the blood through high resistance in the vessels, putting strain on both the heart and the arteries.
High blood pressure also causes the arteries around the body to thicken and become weaker and more rigid. In the long term this increases the risk of complications including strokes, kidney disease and eye damage.
Measuring blood pressure
Blood pressure changes throughout the day, going up during exercise and down during sleep. It can also be affected by feeling anxious. So high blood pressure is diagnosed only once an above-average reading has been taken on a number of different occasions.
A silent killer
- High blood pressure rarely has obvious symptoms
- Untreated high blood pressure increases the risk of heart attacks and strokes
- The only way of knowing if there is a problem is to have your blood pressure measured
Source: NHS Choices
Blood pressure measurements consist of two readings:
- Systolic pressure - the peak force of the blood as the heart beats to pump it around the body
- Diastolic pressure - the pressure of the blood while the heart is relaxed in between beats
Systolic pressure is the larger number of the two readings.
Sometimes kits are given to people to further test their blood pressure at home. This generally happens if they feel anxious at the doctors, which would artificially raise their readings.
Causes of high blood pressure
In over 90% of cases, the cause of high blood pressure is unknown. This is called primary (or essential) hypertension.
In the remaining 10%, it is as a result of an underlying problem, such as kidney disease, abnormalities in the blood vessels, adrenal gland tumours or certain drugs and medicines. This is known as secondary hypertension, and the blood pressure usually returns to normal when the underlying issue is treated.
While there is usually no clear cause of the condition, the risk increases steadily with age. You are also at increased risk if you over 65, are of African/Caribbean descent, or have a relative with high blood pressure. The relationship between these factors and high blood pressure is complex and not fully understood.
Lifestyle-factors that increase the risk include drinking too much alcohol and not doing enough exercise. A recent study suggested eating a high-salt diet could increase the risk of developing the condition by damaging blood vessels over a long period of time.
Smoking a cigarette immediately raises blood pressure as the chemicals in cigarette smoke stimulate the arteries to constrict. These chemicals can also damage the lining of the artery walls, causing them to narrow over time and increase blood pressure in a more chronic way.
Sudden high levels of stress can also cause a dramatic but temporary increase in blood pressure, which may be enough to trigger a brain haemorrhage or stroke.