Aspirin and primary cardiovascular prevention. Uncertain balance between benefits and risks.

Most individuals with no pre-existing cardiovascular disease have a low risk of experiencing arterial thrombosis. Using the standard Prescrire methodology, we reviewed the literature on the risk-benefit balance of aspirin in the primary prevention of cardiovascular events. In the general population, a meta-analysis in 95 456 persons suggests that aspirin has no effect on either total or cardiovascular mortality. Aspirin may slightly reduce the risk of stroke in women and myocardial infarction in men, but it increases the risk of bleeding. It is unclear whether the benefits outweigh the risks. Aspirin does not reduce mortality in the elderly. in one trial, aspirin reduced the risk of ischaemic stroke and myocardial infarction in women aged 65 and over. However, the risk of cerebral haemorrhage associated with aspirin increases with age. Therefore, the risk-benefit balance of aspirin in primary cardiovascular prevention in the elderly is uncertain. Aspirin is more beneficial in patients with cardiovascular risk factors, but the bleeding risk is sometimes higher too. In clinical trials, aspirin did not reduce either total or cardiovascular mortality in hypertensive or diabetic patients. In contrast, it reduced the risk of myocardial infarction in hypertensive patients and diabetic men. Aspirin did not prevent cardiovascular events in smokers, and has not been assessed in patients with hypercholesterolaemia. In practice, the risks outweigh the benefits when aspirin is used to prevent a first thrombotic event in people at low risk. When the cardiovascular risk is higher than in the general population, for example in patients with risk factors, the weak preventive effects of aspirin on myocardial infarction and ischaemic stroke may outweigh the small extra risk of bleeding. The possible value of aspirin for cardiovascular prevention should be discussed with each individual patient. In general, it is preferable to recommend measures with a proven impact on mortality, such as dietary changes, smoking cessation, or drug therapy for patients with risk factors.