Can an aspirin a day keep the doctor away? New research, part of the EU-funded BIOMED (Biomedicine and health) programme, shows it can't all the time. The researchers have discovered that although regular use of aspirin can reduce the rate of non-fatal heart attacks or stroke by around 12%, there is a 33% increase in the risk of internal bleeding in people with no history of relevant disease (primary prevention). The findings are published in The Lancet journal.

Professor Colin Baigent of the Clinical Trial Service Unit and Epidemiological Studies Unit at Oxford University in the UK headed the study, which found that general guidelines supporting the regular use of aspirin in all healthy individuals are unjustified.

"Drug safety really matters when making recommendations for tens of millions of healthy people," he is quoted as saying by The Daily Mail. "And for healthy people, there is not enough evidence to suggest that the benefits of long-term aspirin exceed the risks by a suitable margin," he added.

"Current guidelines largely ignore any differences in bleeding risk, and recommend that aspirin be used widely for primary prevention in those at moderately raised risk of coronary heart disease," the study reads. "It has also been suggested that, since age is a major determinant of the risk of coronary heart disease, daily aspirin should be started in all people above a specific age, either alone or in combination with other drugs."

The researchers, who are members of the 'Antithrombotic Trialists' (ATT) collaboration, evaluated data from more than 95,000 people participating in 6 randomised clinical trials that examined primary prevention with the use of aspirin.

Based on the results, the risk of serious vascular events fell from 0.57% to 0.51% each year because of aspirin treatment, but the risk of major bleeds rose from 0.07% to 0.10% each year. According to the researchers, this indicates that aspirin is not, in fact, a foolproof method for primary prevention.

"In patients who are at high risk because they already have occlusive vascular disease, long-term antiplatelet therapy (e.g. with aspirin) reduces the yearly risk of serious vascular events by about a quarter," the study reads. "This decrease typically corresponds to an absolute reduction of about 10 to 20 per 1,000 in the yearly incidence of non-fatal events, and to a smaller, but still definite, reduction in vascular death."

In the secondary prevention studies, which targeted patients taking aspirin to prevent a repeat attack, the researchers found that aspirin cuts the risk of serious vascular events by about 20%. The reductions in risk were similar for men and women in both sets of trials.

The alternative to primary prevention, say the researchers, is to postpone starting long-term aspirin treatment until some evidence of occlusive vascular disease, which affects arteries and leads to distal arterial insufficiency and ischaemia, is seen.

"The main disadvantage of deferral is that the first manifestation of disease might be a disabling or fatal event, but the main advantage is that it could avoid decades of slightly increased risk of cerebral haemorrhage or major extracranial bleeding," the research shows.

Further trials are already in progress, according to the team.

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