What are the causes of high blood pressure?

There are two types of hypertension:

• primary hypertension (also known as essential hypertension)
• secondary hypertension.

Primary hypertension is far more common accounting for 95% of all cases. It is caused by many different, usually interacting, factors.

Secondary hypertension accounts for 5% of hypertension cases and is caused by a specific abnormality in one of the organs or systems of the body, so is the result of another medical problem.

Primary hypertension affects millions of people yet the basic origins are not always known. Many factors can affect blood pressure, including how much water and salt you have in your body, the condition of your kidneys, nervous system and blood vessels, and the levels of different body hormones.

Although the exact cause of primary hypertension is not always apparent some things are known to put you at a higher risk of developing it.

So if for example you eat a lot of fatty foods, don’t do much exercise and smoke you would be classed as someone at high risk of hypertension.

How these risk factors cause high blood pressure is not clear but to help make the link between risk and hypertension a little more real it’s possible to hypothesise. As an example, it is possible that a high fat diet may lead to a build up of fatty deposits on blood vessel walls. This would cause the vessels to become rough and inflexible and hence make it harder for the blood to pass through, like water trying to flow through a bunged-up pipe. As blood must keep flowing, the body responds by increasing blood pressure to push harder. This is just an example and in fact the different risk factors will contribute to high blood pressure by many diverse but interacting pathways.