Aspirin as primary prevention

Current situation 

  • Many healthy people over the age of 50 years in the UK regularly take aspirin.
  • Patients at high risk of cardiovascular disease (CVD) are still not taking aspirin.
  • The balance of risks versus benefits of aspirin for the prevention of CVD has not been established in the elderly.

What is the evidence?

  • It has been estimated that 90-95 per cent of the population could take low-dosage aspirin without undesirable effects (BMJ 2005; 330: 1,440-1).
  • An observational study in two UK hospitals showed that aspirin was the causal agent in 18 per cent of admissions for adverse drug reactions (BMJ 2004; 329: 15-9).
  • Women derive different benefits to men from low-dosage aspirin for primary prevention of CVD (JAMA 2006; 295: 306-13).
  • Aspirin is the most cost-effective antithrombotic for peripheral arterial disease (Heart 2007; 93: 303-8).
  • US research has found that aspirin significantly lowered all-cause mortality in women with no history of CVD (Arch Intern Med 2007; 167: 562-72).
  • A recent systematic review has shown there is no evidence to support using doses greater than 75-81mg of aspirin per day for CVD prevention, especially because higher dosages are associated with increased GI side-effects (JAMA 2007; 297: 2,018-24).
  • A recent meta-analysis showed that, in absolute terms, treating about 800 patients with low-dosage aspirin for a year would result in one extra serious bleeding event (Am J Med 2006; 119: 624-38).
  • A recent trial showed a reduced incidence of colorectal cancer in patients taking aspirin at 300mg a day for at least five years (Lancet 2007; 369: 1,603-13).

Implications for practice

  • The absolute benefit of aspirin in people aged 55-59 years of age is prevention of around two first myocardial infarctions per 1,000 population per year (BMJ 2005; 330: 1,442-3).
  • However, the excess risks of GI bleeding with aspirin are one to two per 1,000 a year at age 60 and seven per 1,000 a year at age 80.
  • New guidelines issued by the American Heart Association propose replacing the Framingham risk assessment method and adopting more aggressive preventive treatment in women who are currently considered at low risk (Circulation 2007; 115: 1,481-501). The AHA recommends low-dosage aspirin for all women over 65 years.

Dr Louise Newson is a GP in the West Midlands and author of 'Hot Topics for MRCGP and General Practitioners' PasTest 2006


  • - Aspirin is increasingly being taken by healthy people.
  • - Many people taking aspirin are at unnecessary risk of GI haemorrhage.
  • - The benefits of aspirin outweigh risks in those at high cardiovascular risk.
  • - More research is needed before aspirin can be widely advocated.

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