What is the efficacy and safety of aspirin (acetylsalicylic acid) in primary cardiovascular prevention?

Aspirin in Primary Cardiovascular Prevention: Efficacy and Safety

Low-dose aspirin (75-162 mg/day) should NOT be routinely used for primary cardiovascular prevention in most individuals, particularly those aged 60 years or older, as the bleeding risks often outweigh the cardiovascular benefits. 1, 2, 3

Risk-Benefit Assessment

Aspirin's efficacy and safety in primary prevention depends critically on individual cardiovascular risk profiles:

Cardiovascular Benefits

• Reduces nonfatal myocardial infarction by approximately 21% in primary prevention 4
• Does not significantly reduce cardiovascular death in primary prevention settings 4
• Provides minimal to no cardiovascular benefit in adults ≥60 years 3

Bleeding Risks

• Increases major bleeding risk by 29-48% 2
• Major gastrointestinal bleeding: 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: increased by 0-2 per 1,000 persons over 5 years 1, 2

Evidence-Based Recommendations by Population

Adults 40-59 years with ≥10% 10-year CVD risk

• May consider aspirin after shared decision-making 3
• Benefits are small and must be weighed against bleeding risks
• Individuals without increased bleeding risk may be more likely to benefit

Adults ≥60 years

• Aspirin is NOT recommended for initiating primary prevention 3
• For those >70 years, risks clearly outweigh benefits 1, 5

Diabetes patients

• May consider aspirin (75-162 mg/day) for primary prevention in those with increased cardiovascular risk 1
• Requires at least one additional major risk factor (family history of premature ASCVD, hypertension, dyslipidemia, smoking, or CKD/albuminuria)
• Patient should not be at increased bleeding risk 1

Risk Stratification Algorithm

1. Calculate 10-year ASCVD risk using validated calculator

2. Assess bleeding risk factors:

   • Age >70 years
   • History of GI bleeding/ulcers
   • Concurrent anticoagulant or NSAID use
   • Uncontrolled hypertension
   • Renal disease
   • Anemia

3. Apply 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

Important Clinical Considerations

• Coronary calcium scoring may help further tailor aspirin therapy decisions, particularly in those at low risk 1
• Aspirin is contraindicated in individuals <21 years due to risk of Reye syndrome 1
• The lowest effective dose (typically 81 mg in US) should be used to minimize side effects 1
• Uncontrolled hypertension may attenuate aspirin's benefits in reducing CHD 1
• Concurrent use with NSAIDs or anticoagulants significantly increases bleeding risk 2

Common Pitfalls to Avoid

1. Confusing primary and secondary prevention: Aspirin has clear benefits in secondary prevention (established CVD) but limited benefit in primary prevention
2. Ignoring age as a risk factor: Older adults (≥60 years) have higher bleeding risk that typically outweighs potential benefits
3. Overlooking bleeding risk factors: Comprehensive bleeding risk assessment is essential before recommending aspirin
4. Using inappropriate dosing: Higher doses increase bleeding risk without additional cardiovascular benefit

The evidence from recent trials has shifted the risk-benefit balance against routine aspirin use in primary prevention, particularly in older adults where the 2022 USPSTF guidelines now recommend against initiating aspirin therapy in those ≥60 years 3.