When to Recommend Aspirin
For secondary prevention in patients with established cardiovascular disease, recommend aspirin 75-162 mg daily indefinitely; for primary prevention, the landscape has fundamentally shifted—most healthy adults should NOT receive aspirin, with narrow exceptions for select high-risk patients aged 40-70 years who have low bleeding risk and cannot optimally control other cardiovascular risk factors. 1
Secondary Prevention (Established CVD)
Start aspirin immediately and continue indefinitely in all patients with:
- History of myocardial infarction
- Prior stroke or TIA
- Peripheral vascular disease
- Coronary artery bypass grafting (start within 48 hours post-surgery)
- Percutaneous coronary intervention with stenting
- Documented atherosclerotic cardiovascular disease
For aspirin allergy, substitute clopidogrel 75 mg daily 3. After acute coronary syndrome or stent placement, use dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) for up to 12 months 2.
Primary Prevention (No Prior CVD)
The Modern Evidence Has Changed Everything
The 2019 ACC/AHA guidelines represent a major departure from previous recommendations, driven by three pivotal 2018 trials (ASCEND, ARRIVE, ASPREE) showing that bleeding risks now outweigh cardiovascular benefits in most primary prevention populations 4, 1. The number needed to treat to cause major bleeding (210) is actually lower than the number needed to prevent an ASCVD event (265) 4.
Do NOT Recommend Aspirin For:
Adults ≥60 years of age (Class III recommendation) 1, 5
- The ASPREE trial showed increased bleeding and mortality without cardiovascular benefit in this age group 4
Low-risk adults of any age (10-year ASCVD risk <10%) 1
Patients with diabetes alone without additional risk factors 4, 6
- ASCEND trial showed bleeding risks counterbalanced vascular benefits 4
Adults <40 years of age (insufficient evidence) 1
Anyone <21 years of age (contraindicated due to Reye syndrome risk) 3
Consider Aspirin Only For (Class IIb):
Ages 40-59 years with ≥10% 10-year ASCVD risk AND low bleeding risk 1, 5
High-risk features that may tip the balance toward aspirin use:
- Current smokers
- Strong family history of premature ASCVD
- Very elevated cholesterol inadequately controlled with statins
- Coronary artery calcium score ≥100
- Multiple uncontrolled risk factors despite optimal therapy 4
Dose: 75-100 mg daily (81 mg is standard in US) 4, 1
Ages 60-69 years:
May consider in highly select cases with very high ASCVD risk and low bleeding risk, but this is controversial. The USPSTF 2022 recommendation explicitly advises against initiating aspirin in adults ≥60 years 5.
Diabetes-Specific Guidance
The diabetes guidelines have also evolved:
- Primary prevention: Aspirin may be considered for patients ≥50 years with at least one additional major risk factor (family history, hypertension, dyslipidemia, smoking, albuminuria) AND low bleeding risk 3
- However, recent trials show limited benefit even in diabetes 4, 6
- Clinical judgment required—not a blanket recommendation 3
Absolute Contraindications to Aspirin
Never prescribe aspirin if:
- Prior gastrointestinal bleeding
- Known bleeding disorder
- Severe liver disease
- Thrombocytopenia
- Concurrent anticoagulation (relative contraindication—requires careful monitoring)
- Concurrent NSAID use
- Uncontrolled hypertension
- Documented aspirin allergy 4, 1
Critical Clinical Pitfalls
The "aspirin for everyone" era is over. Modern preventive therapy (widespread statin use, better blood pressure control, lower smoking rates) has changed the risk-benefit calculus. In contemporary populations, aspirin's bleeding risks often exceed cardiovascular benefits for primary prevention 4.
Don't use higher doses thinking they're more effective—75-162 mg is optimal; higher doses increase bleeding without improving efficacy 1, 3.
Avoid the trap of prescribing aspirin instead of addressing modifiable risk factors. Aspirin should never substitute for smoking cessation, blood pressure control, statin therapy, or diabetes management 1.
Special Population: Pregnancy
Low-dose aspirin (81 mg daily) is recommended for preeclampsia prevention in high-risk pregnant women, initiated between 12-28 weeks gestation (optimally before 16 weeks) and continued until delivery 7. This is a separate indication from cardiovascular prevention.