https://www.acpjournals.org/doi/full/10.7326/0003-4819-136-2-200201150-00016
For patients without known cardiovascular disease who are similar to those enrolled in the 5 large primary prevention trials, our systematic review suggests that aspirin chemoprevention reduces myocardial infarction but has no effect on ischemic stroke or all-cause mortality over 5 years. Aspirin therapy also increases the risk for gastrointestinal bleeding and hemorrhagic stroke. Aspirin chemoprevention is probably beneficial for patients who have no previous diagnosis of cardiovascular disease but are at high risk for developing coronary heart disease in the next 5 years. Conversely, patients at low risk for coronary heart disease probably do not benefit from and may even be harmed by aspirin because the risk for adverse events may exceed the benefits of chemoprevention (6, 29).
Gastrointestinal Bleeding
Aspirin increased the rates of gastrointestinal bleeding in all 5 primary prevention trials. Detection of events, definition of a “significant” bleeding event, and reporting of location of upper gastrointestinal bleeding varied across trials (Table 5).