What is the recommended dosage of aspirin (acetylsalicylic acid) for an adult patient with a history of cardiovascular disease or risk factors, such as hypertension, hyperlipidemia, or diabetes, requiring low-dose aspirin for cardiovascular risk reduction?

Aspirin 80 mg for Cardiovascular Risk Reduction

For adults with established cardiovascular disease (prior MI, stroke, or revascularization), aspirin 75-100 mg daily (81 mg in the US) is strongly recommended as lifelong therapy, as the cardiovascular benefits far outweigh bleeding risks. 1, 2, 3

Secondary Prevention (Established CVD)

Aspirin 75-162 mg daily should be continued indefinitely in all patients with documented atherosclerotic cardiovascular disease, including those with prior myocardial infarction, stroke, coronary revascularization, or significant obstructive coronary artery disease on imaging. 4, 1, 3 The most common formulation in the US is 81 mg daily, which provides equivalent cardiovascular protection to higher doses while minimizing bleeding complications. 1, 2

• The dose of 75-100 mg daily is optimal for secondary prevention, as demonstrated by the ADAPTABLE trial showing no difference in cardiovascular events or bleeding between 81 mg and 325 mg doses. 4, 1
• For patients with documented aspirin allergy, clopidogrel 75 mg daily should be substituted. 1, 2

Primary Prevention (No Prior CVD)

The decision for primary prevention is more nuanced and depends on age, cardiovascular risk factors, and bleeding risk:

Adults Aged 40-59 Years

Aspirin 75-162 mg daily may be considered for adults aged 40-59 years with a 10-year cardiovascular disease risk ≥10% who are not at increased bleeding risk. 2, 5 However, the net benefit is small and requires careful consideration. 5

Adults with Diabetes

For diabetic patients aged ≥50 years with at least one additional major cardiovascular risk factor (hypertension, dyslipidemia, smoking, family history of premature CVD, or albuminuria), aspirin 75-162 mg daily is reasonable if bleeding risk is low. 4, 1, 2

• Blood pressure must be controlled (<150/90 mmHg) before initiating aspirin to minimize bleeding risk. 1, 2
• The HOT trial demonstrated that aspirin 75 mg daily reduced cardiovascular events by 15% and myocardial infarction by 36% in well-controlled hypertensive patients with diabetes. 1, 2

Adults Aged ≥60 Years

Aspirin should NOT be initiated for primary prevention in adults aged 60 years or older, as bleeding risks outweigh cardiovascular benefits in this age group. 3, 5 For patients over age 70 years without established CVD, the balance clearly favors greater risk than benefit. 4, 1

Low-Risk Patients

Aspirin is NOT recommended for primary prevention in adults at low cardiovascular risk, including men and women aged <50 years with diabetes and no other major risk factors, as bleeding risks outweigh minimal benefits. 4, 1, 3

Dosing Recommendations

The optimal aspirin dose for both primary and secondary prevention is 75-162 mg daily, with 75-81 mg being preferred. 4, 1, 2

• Using the lowest effective dose (75-81 mg) minimizes gastrointestinal bleeding while maintaining efficacy. 4, 2, 3
• Doses >162 mg do not provide additional cardiovascular benefit but significantly increase bleeding risk. 2, 3
• Average daily dosages in clinical trials ranged from 50-650 mg, but doses of 75-162 mg appear optimal. 4

Bleeding Risk Assessment

Major bleeding risk is approximately 2-5 per 1,000 patients per year, with non-fatal major bleeds occurring approximately twice as frequently with aspirin therapy. 1, 3

Absolute Contraindications to Aspirin:

• Active bleeding or recent gastrointestinal bleeding 2, 3
• Known aspirin allergy 1, 2
• Bleeding disorders 2, 3
• Concurrent anticoagulation therapy 2, 3
• Uncontrolled hypertension 1
• Age <21 years (Reye syndrome risk) 1
• History of gastrointestinal ulcers 2
• Clinically active hepatic disease 1

High Bleeding Risk Factors:

• Age >70 years 3
• Anemia 1, 2
• Chronic kidney disease 1, 2
• Concurrent use of NSAIDs, anticoagulants, or corticosteroids 1, 3

Special Considerations

Gender Differences

Aspirin reduces myocardial infarction risk in men but not women, while reducing stroke risk in women but not men in primary prevention. 1, 2 For women ≥65 years with controlled blood pressure and high cardiovascular risk (>6-10% 10-year risk), aspirin 81 mg daily or 100 mg every other day may be considered. 1, 2

Dual Antiplatelet Therapy

Following acute coronary syndrome, dual antiplatelet therapy (aspirin plus a P2Y12 inhibitor such as clopidogrel, ticagrelor, or prasugrel) is recommended for at least 1 year. 4, 1, 3

Proton Pump Inhibitors

Current evidence supports the use of proton pump inhibitors to decrease the risk of recurrent aspirin-related gastrointestinal bleeding, though routine use for primary prevention may not be cost-effective. 4

Common Pitfalls to Avoid

• Do not initiate aspirin in low-risk patients (age <50 years with diabetes and no other major risk factors) where bleeding risks outweigh minimal benefits. 1, 2
• Do not use higher doses (>162 mg) assuming greater cardiovascular protection—they only increase bleeding risk without additional benefit. 2, 3
• Do not start aspirin in patients ≥60 years for primary prevention, regardless of cardiovascular risk, as recent evidence shows no net benefit. 3, 5
• Do not prescribe aspirin without controlling blood pressure first in hypertensive patients, as uncontrolled hypertension significantly increases bleeding risk. 1, 2