Should aspirin be prescribed for primary prevention in an adult without known cardiovascular disease?

Aspirin for Primary Prevention: Current Recommendations

Do not routinely prescribe aspirin for primary prevention in adults without established cardiovascular disease, as bleeding risks now outweigh cardiovascular benefits in most populations. 1, 2

Risk-Based Decision Algorithm

Step 1: Determine if Secondary Prevention Applies

• If the patient has established ASCVD (prior MI, stroke, coronary revascularization, or significant obstructive CAD), aspirin 75-100 mg daily is strongly indicated—this is secondary prevention, not primary prevention. 1
• If no established ASCVD, proceed to primary prevention assessment. 1

Step 2: Screen for Absolute Contraindications

Do not prescribe aspirin if ANY of the following are present: 1, 2

• Age ≥60 years (Grade D recommendation against use) 2, 3
• History of gastrointestinal bleeding or peptic ulcer disease 1, 2
• Active bleeding disorder, thrombocytopenia, or coagulopathy 1, 2
• Concurrent anticoagulation (warfarin, DOACs) 1, 2
• Chronic kidney disease 1, 2
• Uncontrolled hypertension 1, 2
• Regular NSAID or corticosteroid use 1, 2

Step 3: Age-Stratified Approach for Eligible Patients

Ages 40-59 years:

• May consider aspirin 75-100 mg daily ONLY if ALL criteria met: 4, 1, 2
  • 10-year ASCVD risk ≥10% 4, 1
  • No bleeding risk factors present 1, 2
  • Patient willing to take daily medication after shared decision-making 4
• This is a Class IIb recommendation (weak, "may be considered") 1
• The net benefit is small: cardiovascular events prevented approximately equal bleeding episodes induced 2

Ages 60-70 years:

• Generally do not prescribe aspirin for primary prevention 2, 3
• Bleeding risk substantially increases with age (4-12 major bleeds per 1,000 older adults over 5 years vs. 2-4 per 1,000 middle-aged adults) 1, 2

Age ≥70 years:

• Absolute contraindication—harms exceed benefits 1, 2, 3

Special Populations

Diabetes Mellitus

For diabetic patients without established ASCVD: 1, 2

• May consider aspirin 75-162 mg daily ONLY if:
  • Age ≥50 years 1, 2
  • At least one additional major cardiovascular risk factor (family history of premature ASCVD, hypertension, dyslipidemia, smoking, CKD/albuminuria) 1, 2
  • No bleeding risk factors 1, 2
• The ASCEND trial showed 12% reduction in vascular events BUT 29% relative increase in major bleeding (3.2% to 4.1% absolute) 2
• This requires comprehensive shared decision-making 2

Hypertension

For hypertensive patients: 1, 2

• Blood pressure MUST be controlled (<150/90 mmHg) before considering aspirin 2
• Consider aspirin ONLY if age ≥50 years with controlled BP AND either target organ damage, diabetes, or 10-year CVD risk >15% 1, 2
• Uncontrolled hypertension is an absolute contraindication 1, 2

Quantifying the Risk-Benefit Balance

Bleeding risks with aspirin: 1, 2

• Major GI bleeding: 2-4 per 1,000 middle-aged adults over 5 years (4-12 per 1,000 older adults) 1, 2
• Hemorrhagic stroke: 0-2 per 1,000 persons over 5 years 1, 2
• Relative risk of major GI bleeding: 1.6 even with low doses 1, 2

Cardiovascular benefits: 5, 6

• No reduction in all-cause mortality (RR 0.98,95% CI 0.93-1.02) 5
• Modest reduction in myocardial infarction (RR 0.82), but this effect was not evident in more recent trials 5
• The number of cardiovascular events prevented equals the number of bleeding episodes induced in patients with ASCVD risk >1% per year 2

Optimal Dosing When Aspirin Is Prescribed

If aspirin is indicated, use the lowest effective dose: 1, 2

• 75-100 mg daily (81 mg in the United States) 1, 2
• Doses of 75-162 mg daily are acceptable 1, 2
• Higher doses increase bleeding risk without additional cardiovascular benefit 4

Evolution of Guidelines: Why Recommendations Changed

Historical context (2009-2016): 4

• Earlier guidelines recommended aspirin for 10-year CHD risk ≥10-20% 4
• The 2016 USPSTF found moderate certainty of small to moderate net benefit in select populations 4

Current evidence (2019-2025): 1, 2, 5, 6

• Recent large trials (ARRIVE, ASCEND, ASPREE) showed increased bleeding without mortality benefit 5, 6
• The 2019 ACC/AHA downgraded aspirin to Class IIb (weak recommendation) 1
• The 2022 USPSTF issued a Grade D recommendation against routine use in adults ≥60 years 2, 3

Critical Pitfalls to Avoid

Do not prescribe aspirin for low-risk individuals (<10% 10-year ASCVD risk): 1

• Minimal cardiovascular benefit is outweighed by bleeding risk 1

Do not ignore age as a contraindication: 1, 2, 3

• Age ≥60 years substantially increases bleeding risk 2, 3
• Age ≥70 years is an absolute contraindication 1, 2

Do not prescribe aspirin without assessing bleeding risk factors: 1, 2

• Always screen for history of GI bleeding, concurrent anticoagulation, uncontrolled hypertension, and CKD 1, 2

Do not confuse primary and secondary prevention: 1

• Aspirin remains strongly indicated for secondary prevention in established ASCVD 1
• The evidence and recommendations are fundamentally different for these two populations 1

Do not rely on older guidelines: 4, 1, 2

• Recommendations have shifted dramatically since 2019 based on new trial data 1, 2, 5, 6