Being resistant to aspirin could make patients up to four times more likely to suffer from a stroke, according to new research.
A study published in the British Medical Journal states that patients who are "aspirin resistant" have blood platelets which do not respond to aspirin which is often prescribed to prevent blood clots.
There is currently no way of telling who is likely to be aspirin resistant.
The author of the study looked at 20 studies involving cardiovascular patients, 28 per cent of who were resistant to aspirin.
It was found that these patients, regardless of their underlying condition, were at greater risk of heart attack and of dying from a heart attack.
Approximately 39 percent of the aspirin resistant patients suffered from a cardiac event compared with just 16 per cent of the aspirin sensitive participants.
According to the Stroke Association, approximately 150,000 people living in the UK suffer from a stroke each year.
People aged over 65 are the most at risk.
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