Aspirin for the primary prevention of cardiovascular events: an update of the evidence for the U.S. Preventive Services Task Force.

BACKGROUND Coronary heart disease and cerebrovascular disease are leading causes of death in the United States. In 2002, the U.S. Preventive Services Task Force (USPSTF) strongly recommended that clinicians discuss aspirin with adults who are at increased risk for coronary heart disease. PURPOSE To determine the benefits and harms of taking aspirin for the primary prevention of myocardial infarctions, strokes, and death. DATA SOURCES MEDLINE and Cochrane Library (search dates, 1 January 2001 to 28 August 2008), recent systematic reviews, reference lists of retrieved articles, and suggestions from experts. STUDY SELECTION English-language randomized, controlled trials (RCTs); case-control studies; meta-analyses; and systematic reviews of aspirin versus control for the primary prevention of cardiovascular disease (CVD) were selected to answer the following questions: Does aspirin decrease coronary heart events, strokes, death from coronary heart events or stroke, or all-cause mortality in adults without known CVD? Does aspirin increase gastrointestinal bleeding or hemorrhagic strokes? DATA EXTRACTION All studies were reviewed, abstracted, and rated for quality by using predefined USPSTF criteria. DATA SYNTHESIS New evidence from 1 good-quality RCT, 1 good-quality meta-analysis, and 2 fair-quality subanalyses of RCTs demonstrates that aspirin use reduces the number of CVD events in patients without known CVD. Men in these studies experienced fewer myocardial infarctions and women experienced fewer ischemic strokes. Aspirin does not seem to affect CVD mortality or all-cause mortality in either men or women. The use of aspirin for primary prevention increases the risk for major bleeding events, primarily gastrointestinal bleeding events, in both men and women. Men have an increased risk for hemorrhagic strokes with aspirin use. A new RCT and meta-analysis suggest that the risk for hemorrhagic strokes in women is not statistically significantly increased. LIMITATIONS New evidence on aspirin for the primary prevention of CVD is limited. The dose of aspirin used in the RCTs varied, which prevented the estimation of the most appropriate dose for primary prevention. Several of the RCTs were conducted within populations of health professionals, which potentially limits generalizability. CONCLUSION Aspirin reduces the risk for myocardial infarction in men and strokes in women. Aspirin use increases the risk for serious bleeding events.