Aspirin and stroke

Aspirin is one of the most commonly used medicines. It has been used for over 100 years as a painkiller and to reduce fever. Today, Aspirin is widely used in preventing heart attacks and strokes. This factsheet describes how aspirin works to reduce the risk of stroke, when it is commonly used and outlines some of the alternative medications to aspirin.

Aspirin (also called acetylsalicylic acid) is used in a wide variety of conditions, for example to reduce pain in arthritis or to prevent heart attack. Research is also investigating its possible value in diabetes, bowel cancer and dementia. It is useful in such a wide range of conditions because it works in several different ways to prevent and treat illness:

To help prevent strokes and heart attacks, it reduces the risk of blood clots forming in important blood vessels.
To relieve pain and reduce swelling, it blocks the activity of the body’s naturally forming pain-causing chemicals, called prostaglandins.
To lower fever, it acts directly on the temperature regulation centre, which is situated in the brain.

Aspirin and blood clots

Blood clots consist of clumps of blood cells and particles. They are essential for the repair and healing of wounds. However, in blood vessels they can get so big that they block vital arteries, stopping the normal flow of blood.

For a blood clot to form in an artery or vein, tiny solid particles in the blood, called platelets, need to stick together – this is a process called aggregation. This triggers a chain of events that brings in blood cells and proteins. All of these cluster together to form a solid mass called a thrombus, which may eventually cause a blockage.

Aspirin works at an early stage in this process. It can prevent the platelets from sticking together and triggering thrombus formation.

Who should take aspirin?

A stroke can occur in one of two ways. It may arise from a blockage in one of the arteries to the brain (an ischaemic stroke) or a rupture in a blood vessel in the brain, which leads to widespread bleeding in the brain and damage to the surrounding cells (a haemorrhagic stroke). Ischaemic strokes are far more common than haemorrhagic strokes. As well as stroke, tens of thousands of people each year have a transient ischaemic attack (TIA), often called a mini-stroke. The symptoms are the same as those of a full-blown stroke, but they do not last as long (usually from a few minutes to 24 hours).

As with ischaemic strokes, TIAs occur when the blood supply to the brain is impaired because of a temporary blockage in one of the arteries to the brain. People who have a TIA are at greater risk of having a full-blown stroke within a few years if the condition is untreated. Aspirin is only recommended for people who have had an ischaemic stroke or transient ischaemic attack and who are at increased read more