Use of aspirin by people with no history of relevant disease (primary prevention) reduces non-fatal heart attacks by around a fifth—but it also increases the risk of internal bleeding by around a third. Thus its long-term use in this population is of uncertain net benefit since these benefits and risks could cancel each other out. For secondary prevention (among those who already have occlusive vascular disease), aspirin's benefits generally outweigh its small risks. The findings are discussed in an Article published in this week's edition of The Lancet.
In this UK Medical Research Council funded study, Professor Colin Baigent, Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), University of Oxford, UK, and colleagues did an individual patient meta-analysis of serious vascular events (heart attack, stroke, or vascular death) and major bleeds in six primary prevention trials, involving 95,000 people at low-average risk, and 16 secondary prevention trials, involving 17,000 people at high risk. The studies compared long-term aspirin use with control.
The researchers found that in the primary prevention trials, aspirin reduced the already small risk of serious vascular events (stroke, heart attack, vascular death) by 12%, mainly due to the reduction in non-fatal heart attack mentioned above. There was no significant difference in stroke or in vascular mortality, but the small risk of internal bleeds increased by around a third in those given aspirin. In the secondary prevention studies, where people had already had a stroke or heart attack and were at substantial risk of recurrence, aspirin reduced the risk of serious vascular events by about a fifth, and this benefit clearly outweighed any small extra risk of bleeding. In both sets of trials, the proportional reductions in vascular events were similar for men and women.
The authors conclude: "The currently available trial results…do not seem to justify general guidelines advocating the routine use of aspirin in all healthy individuals above a moderate level of risk for coronary heart disease."
Professor Baigent adds*: "Drug safety really matters when making recommendations for tens of millions of healthy people. We don't have good evidence that, for healthy people, the benefits of long-term aspirin exceed the risks by an appropriate margin. If effectiveness is uncertain, then cost-effectiveness calculations are irrelevant."
In an accompanying Comment, Professor Ale Algra and Dr Jacoba P Greving, University Medical Centre Utrecht, Utrecht, Netherlands, use a cost-effectiveness model to create a table** showing which populations might or might not benefit from aspirin in primary prevention — which shows that, in most cases, it is not justified. They conclude: "Patients might not wish to be medicalised —such considerations are important in the decision to take aspirin or not. Whether statins should be preferred above aspirin is a different and difficult question that needs careful consideration too. Apart from drug treatment, one must not forget the importance of lifestyle changes, such as cessation of smoking, healthy diet, and regular exercise."
For Professor Colin Baigent, please contact UK Medical Research Council Press Office T) +44 (0) 20 7637 6011 E) press.office@headoffice.mrc.ac.uk
Professor Ale Algra, University Medical Centre Utrecht, Utrecht, Netherlands T) +31-88-75-59350/59305 E) a.algra@umcutrecht.nl
For full Article and Comment, see: http://press.thelancet.com/aspirin.pdf
Note to editors: *Quote direct from Professor Baigent and cannot be found in text of the Article
**see full Comment for table
Journal
The Lancet