OBJECTIVE: The use of aspirin for primary prevention of cardiovascular events in the general population is controversial. The purpose
of this study was to create a versatile model to evaluate the effects of aspirin in the primary prevention of cardiovascular
events in patients with different risk profiles.
DESIGN: A Markov decision-analytic model evaluated the expected length and quality of life for the cohort’s next 10 years as measured
by quality-adjusted 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 typically 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, gastrointestinal
bleed, ulcer, and death.
MAIN RESULTS: For the cases considered, the effects of aspirin varied according to the cohort’s risk profile. By taking aspirin, the lowest-risk
cohort 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 with a gain of 11.3 quality-adjusted life days. Results without quality adjustment 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 model 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 intervention for patients with no risk factors, and it is beneficial in moderate and high-risk patients. The benefits
of aspirin in this population are comparable to those of other widely accepted preventive strategies. It is especially dependent
on the patient’s risk profile, patient preferences for the adverse effects of aspirin, and on the level of beneficial effects
of aspirin on cardiovascular-related mortality.
Key Words aspirin - primary prevention - cardiovascular disease - decision analysis - risk stratification
Presented in part at the 18th annual meeting of the Society of General Internal Medicine, San Diego, Calif., May 1995.
This manuscript greatly benefited from clinical and methodologic insights from James Dolan, MD. Diane Rivera provided editorial
assistance, and Monica Hamlin provided secretarial support for this manuscript. In addition, the authors would like to thank
both The University of Texas Medical Branch at Galveston and Unidad de Medicina Familiar del Hospital Italiano de Buenos Aires
for their support of Dr. Augustovski during the time which this project was conducted.