What is the current recommendation for daily low‑dose aspirin (81 mg) in adults, including indications for secondary prevention and criteria for primary prevention?

Current Recommendations for Daily Low-Dose Aspirin (81 mg)

Aspirin 75-100 mg daily is strongly recommended for all patients with established cardiovascular disease (secondary prevention), but is generally NOT recommended for primary prevention in most adults due to bleeding risks that approximately equal cardiovascular benefits. 1, 2

Secondary Prevention: Clear Benefit (STRONGLY RECOMMENDED)

For patients with established atherosclerotic cardiovascular disease, aspirin 75-162 mg daily should be started and continued indefinitely. 3, 1

Specific Indications:

• Prior myocardial infarction or acute coronary syndrome – aspirin 75-100 mg daily after initial dual antiplatelet therapy period 1, 4
• History of stroke or transient ischemic attack – aspirin 75-325 mg daily 3
• Documented obstructive coronary artery disease on imaging 1
• Prior coronary revascularization (PCI or CABG) 1, 4
• Symptomatic peripheral artery disease – aspirin 75-325 mg daily 3

The benefits in secondary prevention substantially outweigh bleeding risks – treating 1000 patients for 33 months prevents 33 cardiovascular events, 12 MIs, 25 strokes, and 14 deaths, while causing only 9 major bleeding events. 5

Primary Prevention: Generally NOT Recommended

Age ≥60 Years: DO NOT INITIATE

The USPSTF gives a Grade D recommendation (harm outweighs benefit) against initiating aspirin in adults 60 years or older for primary prevention. 6 The ASPREE trial showed aspirin had no effect on disability-free survival but significantly increased major hemorrhage and unexpectedly increased all-cause mortality in elderly patients. 7

Age 40-59 Years: Consider ONLY in High-Risk Patients

Aspirin may be considered (Grade C recommendation) in adults aged 40-59 with ≥10% 10-year ASCVD risk, but the net benefit is small and requires shared decision-making. 6

Specific Criteria When Aspirin MAY Be Considered:

• 10-year ASCVD risk ≥10% (calculate using ACC/AHA Pooled Cohort Equations) 2, 6
• Diabetes PLUS at least one additional major risk factor (hypertension, dyslipidemia, smoking, family history of premature ASCVD, or albuminuria) 1, 2
• Low bleeding risk (see contraindications below) 2
• Patient willingness to take daily medication after understanding the near-equal trade-off between cardiovascular benefit and bleeding risk 2

The evidence shows that treating 100 patients for 5-10 years prevents approximately 1 cardiovascular event while causing approximately 1 major bleeding event. 2

Recent Trial Evidence Against Primary Prevention:

• ASCEND trial (diabetes patients): 12% reduction in cardiovascular events but 29% increase in major bleeding 2, 7
• ARRIVE and ASPREE trials: No significant cardiovascular benefit with increased bleeding rates 2, 7
• Meta-analyses: Aspirin reduces non-fatal MI by 26% but has minimal effect on cardiovascular mortality (RR 0.95) 3, 2

Absolute Contraindications

Do NOT use aspirin if any of the following are present: 2

• Age >70 years (for primary prevention) 2
• History of gastrointestinal ulcer or recent bleeding 2
• Uncontrolled hypertension 1
• Concurrent anticoagulation (warfarin, DOACs) or chronic NSAID use 1
• Active hepatic disease or bleeding disorder 3
• Anemia or chronic kidney disease 2
• Age <21 years (risk of Reye syndrome) 3, 1
• Documented aspirin allergy 3

Optimal Dosing

The recommended dose is 75-100 mg daily (81 mg tablet in the US) for both primary and secondary prevention. 1, 4

Key Dosing Evidence:

• ADAPTABLE trial: No difference in cardiovascular outcomes or bleeding between 81 mg and 325 mg daily, supporting use of the lower dose 1, 4
• Higher doses (>100 mg) increase gastrointestinal bleeding risk without additional cardiovascular benefit 4
• For acute coronary syndrome: Use loading dose of 162-325 mg initially, then 75-100 mg daily for maintenance 4

Bleeding Risk Quantification

Aspirin increases major bleeding risk by approximately 60% (relative risk 1.6), translating to 2-4 additional major GI bleeds per 1,000 middle-aged adults over 5 years. 3, 1

In real-world practice, major bleeding occurs at approximately 5 per 1,000 patients per year. 2, 4

Alternative Antiplatelet Therapy

For patients with documented aspirin allergy requiring antiplatelet therapy, substitute clopidogrel 75 mg daily. 3, 1, 4

Critical Clinical Pitfalls to Avoid

1. Do NOT initiate aspirin for primary prevention in patients >60 years – the USPSTF explicitly recommends against this due to harm exceeding benefit 6

2. Do NOT prescribe aspirin without first optimizing statin therapy, blood pressure control, and lifestyle modifications – these interventions have stronger evidence for ASCVD risk reduction 2

3. Do NOT continue aspirin in patients who develop new bleeding risk factors – reassess bleeding risk regularly and discontinue if patient ages beyond 70 years or develops contraindications 2

4. Do NOT assume aspirin reduces mortality in primary prevention – the primary benefit is reduction of non-fatal MI, not death 2

5. Recognize sex differences: In primary prevention, aspirin reduces MI in men but not women, while reducing stroke in women but not men 3

When Dual Antiplatelet Therapy is Indicated

After acute coronary syndrome or PCI with stent placement, combine aspirin 75-100 mg daily with a P2Y12 inhibitor (clopidogrel 75 mg, prasugrel 10 mg, or ticagrelor 90 mg twice daily) for at least 12 months. 3, 1