Taking aspirin to prevent heart attack can do more harm than good for healthy individuals without any history of heart attack, revealed a study.
A large number of people - including a substantial number of the "worried well" - take a daily dose of the drug in the belief it will keep them healthy.
However, at a conference for leading doctors, British scientists have claimed that they have found that for healthy people, taking aspirin does not significantly reduce the risk of a heart attack.
The researchers also found that it almost doubles the risk of being admitted to hospital due to internal bleeding.
The findings show that for otherwise healthy people, the risks of taking aspirin outweigh the benefits.
The doctors suggested that the patients who had already suffered a heart attack should continue to take the drug.
They also advised that aspirin could be included in a so-called 'polypill' with an anti-cholesterol statin and a blood pressure drug, which could be taken by everyone aged over 50.
Experts have said that a substantial numbers of 'worried well' take aspirin as a 'just in case' measure believing that because it has been around for such a long time it is completely safe.
The results of the Scottish study have added to the growing evidence that the risks outweigh the benefits for healthy people.
"Our research suggests that aspirin should not be prescribed to the general population at this stage," the Telegraph quoted Prof. Gerry Fowkes, of the Wolfson Unit for Prevention of Peripheral Vascular Disease in Edinburgh, as saying.
He added: "Aspirin probably leads to a minor reduction in future events but the problem is that has to be weighed against an increase in bleeding. Some of that bleeding can be quite serious and lead to death."
Prof. Peter Weissberg, Medical Director of the British Heart Foundation, which part-funded the study, said: "A lot of the worried well buy a small dose of aspirin over the counter not understanding that they are increasing their risk substantially of a major bleed."
He said that it is known that aspirin does reduce the risk of cardiovascular problems but this must be countered against the increased risk of internal bleeding.
In patients who have already had a heart attack the risk of a second is so much higher that the balance is in favour of taking aspirin.
However, for people who have not had a heart attack the risks do not normally outweigh the benefits.
In the study conducted in Scotland 29,000 men and women aged between 50 and 75 were screened to see if they had furred arteries in the legs, which means they are at high risk of developing heart disease but do not yet have symptoms.
More than 3,000 men were randomly assigned to receive a daily dose of aspirin or a dummy pill and were followed up for an average of eight years.
The researchers found no difference in the rate of heart attacks or stroke between the two groups and deaths from any cause were similar.
However, there were 34 major bleeds in people taking aspirin, or two per cent, compared with 20 or 1.2 per cent of those on the placebo.
He said the tablets were only taken 60 per cent of the time during the trial, which reflects real life experience in people who have not had a heart attack.
He said that in secondary prevention, where people have already had one attack and are trying to prevent a second one, compliance is usually better.
The study has been presented at the European Society of Cardiology Congress in Barcelona.