Researchers say the benefits of taking asprin don't outweigh the risks. A new study has shown that, while taking aspirin is beneficial in preventing heart attacks and strokes among people with established cardiovascular disease (secondary prevention), its benefits don’t clearly outweigh the risks in healthy people (primary prevention).
Researchers at the Clinical Trial Service Unit at the University of Oxford analysed data from a number of primary and secondary prevention trials that had compared long-term aspirin use against controls.
In the primary prevention trials, aspirin reduced the risk of a non-fatal heart attack by about one fifth. This corresponds to five fewer such episodes each year for every 10,000 people treated. This is offset by a comparable increase in bleeds with long-term aspirin use. One extra stroke is caused by bleeding and three extra gastrointestinal bleeds occur each year per 10,000 treated.
In the secondary prevention studies, aspirin reduced the risk of a serious vascular event (a heart attack, stroke or cardiovascular death) by about a fifth. But the risk of an event is much higher among people with established cardiovascular disease, so that there were 150 fewer such events each year for every 10,000 patients treated. This large benefit greatly exceeds the risk of bleeding.
We don’t have good evidence that, for healthy people, the benefits of long-term aspirin exceed the risks by an appropriate margin.
In both sets of trials, the risk of a serious vascular event was reduced to a similar degree in both men and women.
Previous reviews of primary prevention trials have led to guidelines recommending that aspirin be used widely among healthy people who are more at risk of coronary heart disease, having raised blood cholesterol or blood pressure for example.
But the new analyses show that many people with above average risk of coronary heart disease are also at above average risk of suffering a bleed, so this method of selecting whom to treat may not be appropriate.
Professor Colin Baigent, an MRC scientist who led the work at the Clinical Trial Service Unit, says: ‘The primary prevention trials were completed some years ago, when modern drugs such as statins were not widely available. Nowadays, primary prevention with statins and other drugs can safely half the risk of heart attacks and strokes.’
University of Oxford
