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

Overview

Cardiovascular disease is a leading cause of death in the U.S. In order to investigate the relationship between aspirin use and cardiovascular disease, the authors conducted a systematic review of existing evidence on the benefits and harms of taking aspirin for the primary prevention of heart attacks, strokes and cardiovascular disease death. This analysis was part of the process of determining national guidelines for aspirin use set by the U.S. Preventive Services Task Force (USPSTF), and an update to the 2002 recommendations. Based on this analysis, the USPSTF suggested that clinicians discuss aspirin use with adults who are at increased risk of developing heart disease or stroke. The authors found that aspirin reduced the incidence of heart disease in people who have never had a stroke or heart attack and that these effects differed by gender, with a reduction of heart attacks in men and strokes in women.

Methodology

The authors conducted a systematic review of all existing evidence through August 2008, which included 95,456 participants who had never had a heart attack or ischemic stroke. The main outcome of interest was the development of cardiovascular disease. In addition, they examined gastrointestinal tract bleeding, hemorrhagic strokes and death. The analysis evaluated the evidence on aspirin separately by gender. This study largely used the analysis of past studies published by Berger and colleagues in 2006. They found only a few new sources of information on the effects of aspirin published after 2001, but the Women’s Health Study was notable in this respect. Aspirin dose in the studies analyzed ranged from 100 mg every other day to 500 mg daily.

Results

  • The analysis of evidence on aspirin by gender demonstrated that aspirin use reduced cardiovascular events in patients without past heart attacks or strokes.

  • Men 45 to 79 years old suffered fewer heart attacks and women 55 to 79 years old experienced fewer ischemic strokes.

  • Aspirin did not seem to affect death from cardiovascular disease or death from all possible causes in either men or women.

  • The use of aspirin increased the risk for major bleeding events, primarily gastrointestinal (stomach) bleeding events, in both men and women.

  • Men, but not women, appear to be at increased risk of hemorrhagic (bleeding) strokes with aspirin use.

Conclusions

  • Aspirin reduces the incidence of heart attacks in men and strokes in women. Men 45 to 79 years old suffered fewer heart attacks and women 55 to 79 years old experienced fewer ischemic strokes (strokes caused by clots in the blood vessels of the brain). There was insufficient data from past studies to determine whether aspirin reduced cardiovascular deaths or deaths from all causes in either men or women.

  • Aspirin’s harmful effects include the increase in the risk for major bleeding events, primarily gastrointestinal (stomach) bleeding events, in both men and women. Men, but not women, appear to be at an increased risk of hemorrhagic (bleeding) strokes with aspirin use.

  • It is not immediately obvious which groups (men or women) obtain benefits that outweigh harms. Aspirin reduces the risk for myocardial infarction in men and for strokes in women, but also increases the risk for serious bleeding events. The authors point out many limitations in the evidence, including great variations in the aspirin doses studied in the various trials and the unusual populations (for example, physicians) studied in some trials.