Aspirin for primary prevention of cardiovascular events

OBJECTIVE: The use of aspirin for primary prevention of cardiovascular even ts in the general population is controversial. The purpose of this study wa s to create a versatile model to evaluate the effects of aspirin in the pri mary prevention of cardiovascular events in patients with different risk pr ofiles. DESIGN:A Markov decision-analytic model evaluated the expected length and q uality of life for the cohort's next 10 years as measured by quality-adjust ed survival for the options of taking or not taking aspirin. SETTING: Hypothetical model of patients in a primary care setting. PATIENTS: Several cohorts of patients with a range of risk profiles typical ly seen in a primary care setting were considered. Risk factors considered included gender, age, cholesterol levels, systolic blood pressure, smoking status, diabetes, and presence of left ventricular hypertrophy. The cohorts were followed for 10 years. Outcomes were myocardial infarction, stroke, g astrointestinal bleed, ulcer, and death. MAIN RESULTS: For the cases considered, the effects of aspirin varied accor ding to the cohort's risk profile. By taking aspirin, the lowest-risk cohor t would be the most harmed with a loss of 1.8 quality-adjusted life days by taking aspirin; the highest risk cohort would achieve the most benefit wit h a gain of 11.3 quality-adjusted life days. Results without quality adjust ment favored taking aspirin in all the cohorts, with a gain of 0.73 to 8.04 days. The decision was extremely sensitive to variations in the utility of taking aspirin and to aspirin's effects on cardiovascular mortality. The m odel was robust to other probability and utility changes within reasonable parameters. CONCLUSIONS: The decision of whether to take aspirin as primary prevention for cardiovascular events depends on patient risk. It is a harmful interven tion for patients with no risk factors, and it is beneficial in moderate an d high-risk patients. The benefits of aspirin in this population are compar able to those of other widely accepted preventive strategies. It is especia lly dependent on the patient's risk profile, patient preferences for the ad verse effects of aspirin, and on the level of beneficial effects of aspirin on cardiovascular-related mortality.