Is aspirin (acetylsalicylic acid) recommended for 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 the bleeding risks generally outweigh the cardiovascular benefits. 1, 2, 3

Recommendations Based on Age and Risk Profile

Adults aged 60 years or older

• Aspirin should NOT be initiated for primary prevention of cardiovascular disease regardless of cardiovascular risk 1, 2, 3
• The 2019 ACC/AHA guidelines explicitly state this as a Class III: Harm recommendation with Level B-R evidence 1
• The USPSTF (2022) concludes with moderate certainty that initiating aspirin in this age group has no net benefit 3

Adults aged 40-59 years

• Aspirin might be considered only in select individuals who:
  • Have 10% or greater 10-year ASCVD risk 1, 2, 3
  • Have no increased bleeding risk 1, 2
  • Are willing to take low-dose aspirin daily 3
• This is a Class IIb recommendation with Level A evidence per ACC/AHA 1
• The benefit in this group is small and requires shared decision-making 3

Adults under 40 years

• Aspirin is not recommended for primary prevention in individuals with low ASCVD risk 1, 2
• Aspirin is contraindicated in patients under 21 years due to risk of Reye syndrome 1, 2

Assessing Cardiovascular Risk

Before considering aspirin for primary prevention, calculate 10-year ASCVD risk using a validated calculator 2. For patients with diabetes, consider aspirin only if:

• Age >50 years with at least one additional major risk factor (family history of premature ASCVD, hypertension, dyslipidemia, smoking, or chronic kidney disease/albuminuria) 1
• Not at increased bleeding risk 1

Bleeding Risk Assessment

Aspirin should not be administered for primary prevention in adults of any age who are at increased bleeding risk 1. Major bleeding risk factors include:

• Age >70 years 1, 2
• History of gastrointestinal bleeding or peptic ulcer disease 2
• Concurrent use of medications that increase bleeding risk (NSAIDs, steroids, anticoagulants) 2
• Thrombocytopenia or coagulopathy 1
• Chronic kidney disease 1, 2
• Uncontrolled hypertension 2
• Anemia 2

Dosing Considerations

If aspirin is deemed appropriate for primary prevention:

• Use the lowest effective dose (75-100 mg daily) 1, 2
• In the US, the most common low-dose tablet is 81 mg 1

Evolving Evidence

Recent large randomized clinical trials have shown diminished benefits of aspirin for primary prevention compared to older studies:

• Contemporary trials show little to no benefit and even suggest net harm 4, 5
• Modern preventive therapies (statins, blood pressure control) have reduced the incremental benefit of aspirin 6
• Major bleeding risk is estimated at 2-4 per 1,000 middle-aged persons and 4-12 per 1,000 older persons given aspirin for 5 years 1, 2
• Hemorrhagic stroke risk increases by 0-2 per 1,000 persons over 5 years 1, 2

Common Pitfalls in Aspirin Use

• Overuse: 26.9% of adults take aspirin without appropriate indications 7
• Underuse: 54% of adults for whom aspirin is indicated are not taking it 7
• Failure to reassess: Not reconsidering aspirin use as patients age and bleeding risk increases 2
• Confusion between primary and secondary prevention: Aspirin remains strongly recommended for secondary prevention in patients with established cardiovascular disease 2, 6

Remember that these recommendations apply only to primary prevention. For patients with established ASCVD, aspirin for secondary prevention has far greater benefit than risk and is still strongly recommended 1, 2.