Aspirin for the Primary Prevention of Cardiovascular Disease: In Need of Clarity.

Aspirin remains one of the most extensively studied cardiovascular medications in the history of medicine. However, despite multiple, well-designed, large randomized controlled trials evaluating the potential of aspirin to prevent cardiovascular events in individuals without known cardiovascular disease (CVD), the role of aspirin in primary prevention is currently unclear. The initial aspirin trials included largely low-risk individuals with primary outcomes mostly focused on myocardial infarction (MI) and stroke, and showed a significant reduction in these CVD outcomes, especially MI. The more recently conducted trials have focused on older, higher CVD risk populations with high rates of lipid-lowering and antihypertensive medications use. These studies have used broader CVD outcomes as their primary end points and have failed to show a significant benefit of aspirin therapy in primary prevention. The exact reasons for the lack of efficacy in these recent trials are unclear but may be related to low rate of atherothrombotic events relative to other CVD events in the populations studied. Four large randomized controlled trials are currently underway which should provide some clarity in determining the optimal use of aspirin in the primary prevention of CVD.