Coronary artery disease
Meta-Analysis of Data from the Six Primary Prevention Trials of Cardiovascular Events Using Aspirin

https://doi.org/10.1016/j.amjcard.2006.04.012Get rights and content

Until recently, 5 major studies have formed the basis for the use of aspirin (acetylsalicylic acid) in primary prevention of cardiovascular (CV) events. Despite these data, the role of aspirin in primary prevention has not been established firmly. Six randomized trials have evaluated the benefits of aspirin for the primary prevention of CV events: the British Doctors’ Trial, the Physicians’ Health Study, the Thrombosis Prevention Trial, the Hypertension Optimal Treatment study, the Primary Prevention Project, and the Women’s Health Study. The combined sample consists of 47,293 subjects on aspirin and 45,580 not on aspirin or placebo. A meta-analysis of these 6 trials assessed 6 CV end points: total coronary heart disease (CHD), nonfatal myocardial infarction (MI), total CV events, stroke, CV mortality, and all-cause mortality. No covariate adjustment was performed and appropriate tests for treatment effect, heterogeneity, and study size bias were applied. Using odds ratios and confidence intervals, the meta-analysis suggested superiority of aspirin for total CHD, nonfatal MI, and total CV events (p ≤0.001 in each case), with a nonsignificant trend (0.07 < p <0.34) for decreased risk of stroke, CV mortality, and all-cause mortality. There was no evidence of statistical bias (p >0.05). Given the study size and cohort, aspirin decreased the risk of CV events in this large patient sample. In conclusion, primary prevention with aspirin decreased the risk of total CHD, nonfatal MI, and total CV events, but there were no significant differences in the incidences of stroke or CV mortality.

Section snippets

Methods

The United States Preventive Services Task Force described the data collection and analysis from the first 5 primary prevention trials (BDT, PHS, TPT, HOT, and PPP)3 and, with the addition of the new data from the WHS,4 is the key source of data.

Because aspirin could have a differential effect on different aspects of CV disease, outcomes were classified as follows: (1) total CHD as nonfatal and fatal MI and death due to CHD; (2) nonfatal MI as confirmed MI that did not result in death; (3)

Results

Among the trials in the analysis, there were 47,293 subjects who were treated with aspirin and 45,580 who received placebo/control.

Table 2 lists each study and indicates if statistical significance of aspirin over placebo was reached when using the odds ratio in any of the end points or groups of end points. Overall, these data provide clear evidence of the benefit of aspirin in total CHD, nonfatal MI, and total CV events and a positive trend for all-cause mortality; these effects are

Discussion

Patients without any apparent history of CV disease were enrolled in the 6 large, randomized, primary prevention trials, and systematic analysis of the outcomes from these trials suggests that aspirin decreases the incidence of CHD events, nonfatal MI, and CV events. However, aspirin had no statistically significant effect on stroke, fatal CHD, or all-cause mortality. Whether there is an overall benefit of aspirin therapy in patients at low to moderate CV risk has been discussed elsewhere and is

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    This study was supported by an unrestricted research grant from Bayer HealthCare LLC, Morristown, New Jersey.

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