Aspirin for all? No
Last edited 7th June 2009
Since medical school, I have always been struck by the number of patients of all ages who live life by the “aspirin-a-day” mantra. In people who have had heart attacks or strokes, aspirin reduces further events by 25%. This beneficial effect is known as “secondary prevention”, and outweighs aspirin’s bleeding risk [1, 2].
However, the role of aspirin in primary prevention (i.e. in patients who have not yet had a heart attack or stroke) has been less clear because the risks of heart attacks and stroke are lower in these patients. Therefore, the measurable benefit of aspirin will be less, especially when we consider it against the bleeding risk. However, current guidelines tend to recommend aspirin in people at risk of heart attacks and ignore the bleeding risk . Alternatively, they advocate aspirin for all patients above a certain age, either alone or in combination with other drugs [4, 5]. As an example, for diabetic patients, there is no trial data to suggest use of aspirin in primary prevention of cardiovascular disease, and yet it is widely used .
Thankfully, the big guns of meta-analysis (studying overall effects of drugs across different randomised controlled trials), the Antithrombotic Trialists' (ATT) Collaboration in Oxford, have put our doubts to bed. They looked through the individual patient data for an astounding 95 000 patients at low risk of cardiovascular disease, in 22 different trials to answer this question . The main finding was a 12% reduction in serious vascular events per year with a 20% reduction in heart attacks, but no significant reduction in stroke. There was a 54% increased risk of major bleeding in patients taking aspirin compared with no aspirin. Interestingly, the risk factors for coronary heart disease also predicted risk of bleeding complications.
Most people were not taking cholesterol-reducing statin therapy during the trials. Statins have been shown to half the risk of cardiovascular disease and are now widely used, so the authors speculate that the actual cardiovascular benefit of aspirin in primary prevention may now be even less. The bottom line is that we should only give aspirin to people after and not before they have had heart attacks or stroke.
- Collaborative overview of randomised trials of antiplatelet therapy--I: Prevention of death, myocardial infarction, and stroke by prolonged antiplatelet therapy in various categories of patients. BMJ. 1994 Jan 8;308(6921):81-106. Antithrombotic Trialists' Collaboration.
- Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. BMJ. 2002 Jan 12;324(7329):71-86. Antithrombotic Trialists' Collaboration.
- JBS 2: Joint British Societies' guidelines on prevention of cardiovascular disease in clinical practice. Heart. 2005 Dec; 91 Suppl 5:v1-52. British Cardiac Society; British Hypertension Society; Diabetes UK; HEART UK; Primary Care Cardiovascular Society; Stroke Association.
- Aspirin for everyone older than 50? For. BMJ. 2005 Jun 18;330(7505):1440-1. Review. Elwood P, Morgan G, Brown G, Pickering J.
- A strategy to reduce cardiovascular disease by more than 80%. BMJ. 2003 Jun 28; 326:1419. Wald NJ, Law MR.
- Primary prevention of cardiovascular events in diabetes: is there a role for aspirin? Nat Clin Pract Cardiovasc Med. 2009 Mar; 6(3):168-9. Price HC, Holman RR.
- Aspirin in the primary and secondary prevention of vascular disease: collaborative meta-analysis of individual participant data from randomised trials. Lancet. 2009 May 30; 373:1849-60. Antithrombotic Trialists' (ATT) Collaboration, Baigent C, Blackwell L, Collins R, Emberson J, Godwin J, Peto R, Buring J, Hennekens C, Kearney P, Meade T, Patrono C, Roncaglioni MC, Zanchetti A.