Do they need to start aspirin?

Aspirin Initiation Decision

For primary prevention, aspirin should generally NOT be started, as the bleeding risk equals or exceeds the cardiovascular benefit in most patients. 1

Clinical Context Assessment

The decision to start aspirin depends entirely on whether this is for primary prevention (no prior cardiovascular events) or secondary prevention (established cardiovascular disease). This distinction is critical because the risk-benefit profile differs dramatically between these two scenarios. 2, 1

For Secondary Prevention (Established ASCVD)

Start aspirin 75-162 mg daily immediately if the patient has documented atherosclerotic cardiovascular disease including prior myocardial infarction, stroke, coronary artery disease, or peripheral artery disease. 2 The benefit far outweighs bleeding risk in this population, with aspirin reducing serious vascular events and mortality. 2

• Recommended dose: 81 mg daily (most common low-dose tablet in the US) 2
• The ADAPTABLE trial demonstrated no difference in cardiovascular events or major bleeding between 81 mg and 325 mg daily, supporting use of the lower dose to minimize side effects. 2, 3
• Continue indefinitely unless contraindicated by active bleeding, severe bleeding risk, or allergy. 2

For Primary Prevention (No Prior Cardiovascular Events)

Do NOT routinely start aspirin for primary prevention, as recent evidence demonstrates the bleeding risk approximates or exceeds the cardiovascular benefit. 1

Age-Based Algorithm:

Age >70 years: Do not start aspirin - bleeding risk clearly outweighs benefit. 2, 1

Age <40 years: Insufficient evidence to recommend aspirin; generally not indicated. 1

Age 40-70 years: Consider aspirin ONLY if ALL of the following criteria are met: 2, 1

• High ASCVD risk (diabetes PLUS at least one additional major risk factor: family history of premature ASCVD, hypertension, dyslipidemia, smoking, or chronic kidney disease/albuminuria) 2
• Low bleeding risk (no history of gastrointestinal bleeding, peptic ulcer disease, thrombocytopenia, coagulopathy, severe renal disease, or concurrent medications increasing bleeding risk) 2
• Shared decision-making discussion documenting that patient understands the comparable risks of bleeding versus cardiovascular benefit 2, 1

Evidence Supporting Caution in Primary Prevention:

The ASCEND trial in diabetic patients without established cardiovascular disease showed aspirin reduced serious vascular events by 12% (8.5% vs 9.6%) but increased major bleeding from 3.2% to 4.1% over 7.4 years of follow-up. 2 For adults with ASCVD risk >1% per year, the number of cardiovascular events prevented equals the number of bleeding episodes induced. 2

Special Populations

Diabetes patients: Even with diabetes, aspirin for primary prevention requires the presence of additional major risk factors AND low bleeding risk, with careful shared decision-making. 2 Previous trials in diabetic patients failed to consistently show significant ASCVD reduction. 2

Age <21 years: Aspirin is contraindicated due to Reye syndrome risk. 2

Patients already on aspirin for primary prevention: Strongly consider discontinuation, especially if age >70 years or if bleeding risk factors have developed. 1 Reassess the risk-benefit profile based on current evidence showing limited benefit. 1

Common Pitfalls to Avoid

• Do not prescribe aspirin reflexively for diabetes alone without assessing additional ASCVD risk factors and bleeding risk. 2
• Do not use higher doses (325 mg) for chronic prevention - doses >75-81 mg do not enhance efficacy but increase gastrointestinal bleeding. 4
• Do not continue aspirin in elderly patients (>70 years) for primary prevention - the evidence clearly shows net harm. 2, 1
• Do not start aspirin without documenting a shared decision-making discussion when used for primary prevention in the 40-70 age group. 2