When is aspirin (acetylsalicylic acid) prescribed for primary or secondary prevention of cardiovascular events?

Aspirin Prescription Guidelines for Cardiovascular Prevention

Aspirin should be prescribed for secondary prevention in all patients with established cardiovascular disease, while primary prevention should be limited to adults aged 40-59 years with ≥10% 10-year cardiovascular risk who are not at increased bleeding risk. 1, 2

Primary Prevention

Risk Assessment Algorithm

1. Calculate 10-year ASCVD risk using validated risk calculator
2. Assess bleeding risk factors:
   • Age >70 years
   • History of GI bleeding
   • Concurrent medications increasing bleeding risk
   • Renal disease or anemia

Recommendations by Age and Risk Category

Ages 40-59 years:

• High CV risk (≥10% 10-year risk) + Low bleeding risk:

  • Consider aspirin 75-100mg daily (81mg preferred) 1, 2
  • Shared decision-making recommended
  • Benefits likely outweigh harms

• High CV risk + High bleeding risk:

  • Avoid aspirin
  • Focus on other preventive strategies (statins, blood pressure control)

• Low CV risk (<10% 10-year risk):

  • Aspirin NOT recommended regardless of bleeding risk 1
  • Potential harms outweigh benefits

Ages ≥60 years:

• Aspirin NOT recommended for initiating primary prevention 2
• Risk of bleeding complications increases substantially with age
• No net benefit demonstrated in this age group

Ages <40 years:

• Aspirin generally NOT recommended unless exceptional risk factors present
• Aspirin contraindicated in patients <21 years due to risk of Reye syndrome 3, 1

Special Populations for Primary Prevention

Diabetes:

• Consider aspirin 75-162mg daily for adults >50 years with at least one additional major risk factor:
  • Family history of premature ASCVD
  • Hypertension
  • Dyslipidemia
  • Smoking
  • Chronic kidney disease/albuminuria 3

Secondary Prevention

Established ASCVD:

• Aspirin 81mg daily recommended indefinitely unless contraindications develop 1
• Applies to patients with:
  • Prior myocardial infarction
  • Prior stroke or TIA
  • Peripheral arterial disease
  • Coronary artery disease

Acute Cardiovascular Events:

• Acute myocardial infarction: Loading dose 162-325mg, then 81mg daily 1
• Acute ischemic stroke: 160-325mg daily initially 1
• After coronary stent placement: 81mg daily indefinitely 1

Dosing Considerations

• Optimal dose: 75-162mg daily (81mg preferred in US) 1, 4
• Higher doses (>100mg) increase bleeding risk without additional cardiovascular benefit 1, 4
• Enteric-coated preparations do not clearly reduce adverse gastrointestinal effects 3

Risk Factors That Increase Bleeding Risk

• Age >70 years
• History of GI bleeding or peptic ulcer disease
• Concurrent use of anticoagulants or NSAIDs
• Uncontrolled hypertension
• Renal disease or anemia 1

Monitoring and Follow-up

• Regular reassessment of cardiovascular and bleeding risk
• Consider adding proton pump inhibitor for patients at higher risk for GI bleeding
• Discontinue if bleeding complications occur or risk/benefit ratio changes 1

Common Pitfalls to Avoid

1. Prescribing aspirin for primary prevention in low-risk individuals - benefits rarely outweigh risks
2. Continuing aspirin in patients >70 years for primary prevention - bleeding risk increases substantially with age
3. Using doses >100mg daily - increased bleeding risk without additional cardiovascular benefit
4. Failing to account for bleeding risk factors when making prescribing decisions
5. Prescribing aspirin with uncontrolled hypertension - may attenuate cardiovascular benefits 3

Aspirin remains a cornerstone of secondary prevention but has a much more limited role in primary prevention based on current evidence. The decision to use aspirin for primary prevention requires careful assessment of both cardiovascular and bleeding risks, with the understanding that the net benefit is modest at best and potentially harmful in older adults.