What are the guidelines for aspirin (acetylsalicylic acid) use in primary prevention of cardiovascular events?

Aspirin for Primary Prevention of Cardiovascular Disease

Aspirin is NOT recommended for routine primary prevention of cardiovascular disease in most individuals, particularly those aged 60 years or older, as bleeding risks outweigh cardiovascular benefits. 1

Current Recommendations Based on Age and Risk

Age-Based Recommendations

• Age ≥60 years: Aspirin is NOT recommended for primary prevention regardless of cardiovascular risk 1
• Age 40-59 years: Aspirin may be considered only in select individuals with:
  • ≥10% 10-year ASCVD risk
  • Low bleeding risk
  • Shared decision-making required 1
• Any age with high bleeding risk: Aspirin is NOT recommended 1

Risk Assessment

Before considering aspirin therapy, two critical assessments must be performed:

1. Cardiovascular Risk Assessment:

   • Calculate 10-year ASCVD risk using validated calculator
   • High risk defined as ≥10% 10-year risk 1

2. Bleeding Risk Assessment:

   • Evaluate for bleeding risk factors:
     • Age >70 years
     • History of GI bleeding/ulcers
     • Concurrent anticoagulant or NSAID use
     • Uncontrolled hypertension
     • Renal disease
     • Anemia
     • Thrombocytopenia
     • Coagulopathy
     • Chronic kidney disease 1

Decision Framework

Age	CV Risk	Bleeding Risk	Recommendation
40-59	≥10%	Low	Consider aspirin 75-162 mg/day
40-59	<10%	Any	Aspirin NOT recommended
≥60	Any	Any	Aspirin NOT recommended
Any	Any	High	Aspirin NOT recommended

Dosage When Appropriate

• If aspirin is deemed appropriate, use the lowest effective dose (75-100 mg daily) 1
• In the US, the most common low-dose tablet is 81 mg 1

Benefits vs. Risks

Potential Benefits (When Used Appropriately)

• Modest reduction in non-fatal myocardial infarction 2, 3
• Limited impact on stroke in primary prevention 3
• No significant reduction in vascular mortality in primary prevention 3

Potential Risks

• Increases major bleeding risk by 29-48% 1
• Major GI bleeding: 2-4 per 1,000 middle-aged individuals and 4-12 per 1,000 older individuals over 5 years 1
• Hemorrhagic stroke risk increases by 0-2 per 1,000 persons over 5 years 1

Historical Context and Evolution of Guidelines

The recommendations for aspirin in primary prevention have evolved significantly over time. Earlier guidelines (such as those from 2002) were more permissive about aspirin use 4, but recent evidence has led to more restrictive recommendations.

The 2021 evidence review concluded that recent trials showed either no benefit or only modest benefit on combined ischemic endpoints, without impact on hard cardiovascular events, while consistently showing increased bleeding risk 2. This has led to the current restrictive stance on aspirin for primary prevention.

Common Pitfalls to Avoid

1. Confusing primary and secondary prevention: Aspirin has clear benefits for secondary prevention (established CVD) but limited benefit for primary prevention 1, 3
2. Overlooking bleeding risk factors: Always assess bleeding risk before recommending aspirin 1
3. Abrupt discontinuation in patients with established CVD: This increases risk of cardiovascular events - aspirin should not be discontinued in these patients 1
4. Using aspirin in patients <21 years: Contraindicated due to risk of Reye syndrome 1
5. Failing to use appropriate dosing: Higher doses increase bleeding risk without additional cardiovascular benefit 1

The shift in guidelines reflects improved understanding of aspirin's risk-benefit profile in primary prevention, with current evidence clearly showing that for most individuals, especially those ≥60 years, the bleeding risks outweigh the modest cardiovascular benefits.