Reevaluating Aspirin's Role in Primary Prevention: Balancing Ischemic Benefit and Bleeding Risk

Overview

Recent meta-regression analyses incorporating data from major trials suggest that aspirin's benefit in primary prevention increases with baseline cardiovascular risk, while bleeding risk also rises but less steeply. This divergence supports aspirin use in patients with a 10-year major adverse cardiovascular event (MACE) risk exceeding 10-20%, even without overt atherosclerosis.

Background

Aspirin has long been established for secondary prevention of cardiovascular events, but its role in primary prevention remains controversial due to inconsistent trial results. Large trials such as ASPREE, ARRIVE, and ASCEND failed to conclusively demonstrate net benefit, largely due to bleeding risks. Recent analyses propose that baseline cardiovascular risk modulates the benefit-risk balance, suggesting aspirin may be more appropriate in higher-risk primary prevention populations. This report reevaluates aspirin's efficacy and safety using updated meta-regression incorporating recent evidence.

Data Highlights

The meta-regression model assessed the absolute risk difference per 100 patient-years for major adverse cardiovascular events (MACE) and major bleeding across studies stratified by baseline 10-year cardiovascular risk. Results showed a statistically significant increase in ischemic event reduction with rising baseline risk (P < 0.05). Bleeding risk also increased with baseline risk but at a less steep slope, resulting in a widening benefit-risk gap at higher risk levels. Notably, evidence is sparse for patients with >20% 10-year risk, highlighting a gap in trial data.

Key Findings

• Aspirin's protective effect against MACE increases significantly with higher baseline cardiovascular risk.
• Major bleeding risk also rises with baseline risk but less steeply than ischemic event reduction.
• The net benefit of aspirin widens as cardiovascular risk exceeds approximately 10-20% over 10 years.
• Current evidence gaps exist for patients with very high cardiovascular risk (>20% 10-year risk).
• Shared decision-making is essential, emphasizing aspirin's uncertainties and the importance of concurrent lifestyle and pharmacologic preventive measures.
• Bleeding risk mitigation strategies, such as taking aspirin with meals and proton pump inhibitor use, are recommended.

Clinical Implications

Clinicians should consider aspirin for primary prevention in patients with moderate to high cardiovascular risk (10-20% 10-year MACE risk), even in the absence of overt atherosclerosis. Aspirin should be prescribed alongside optimized blood pressure control, lipid-lowering therapy, and lifestyle interventions. Patient education on bleeding risks and preventive strategies is critical to maximize net benefit.

Conclusion

Updated meta-regression analyses support a nuanced, risk-based approach to aspirin use in primary prevention, favoring its use in patients with sufficiently elevated cardiovascular risk while emphasizing individualized decision-making and bleeding risk mitigation.

References

1. ASPREE Trial 2018 -- Aspirin in the Elderly
2. ARRIVE Trial 2018 -- Aspirin for Primary Prevention
3. ASCEND Trial 2018 -- Aspirin in Diabetes
4. TIPS-2 Study -- Aspirin Added to Polypill Therapy
5. 2022 US Preventive Services Task Force Recommendation Statement