Journals club - Aspirin for primary prevention

Curriculum statement 15.1 Cardiovascular problem

Scans showing heart at rest (right) and during ischaemic exercise (left)
Scans showing heart at rest (right) and during ischaemic exercise (left)

Key trials

  • A significant number of patients prescribed aspirin as antithrombotic therapy have major adverse vascular-related events each year (N Engl J Med 2005; 353: 2373-83).
  • One study showed that reduction in risk of MI and ischaemic stroke with low-dosage aspirin in elderly people (≥70 years) may be offset by inc-reased cases of serious bleeding (BMJ 2005; 330: 1306).
  • Many patients with cardiovascular disease (CVD) are 'resistant' or non-responsive to aspirin and are therefore more at risk of adverse cardiovascular events (BMJ 2008; 336: 195-8).
  • Women derive different benefits to men from taking low-dosage aspirin for primary prevention of CVD. This study found that the NNT to prevent one cardiovascular event over 6.4 years was 333 women and 270 men (JAMA 2006; 295: 306-13).

Evidence base

  • A recent meta-analysis has shown that the risks of taking aspirin for primary prevention outweigh the benefits. The researchers conclude by stating that the results do not justify the current guidelines recommending the use of aspirin in healthy people with a raised CVD risk (Lancet 2009; 373: 1849-60).
  • One analysis has shown that treatment with aspirin is cost-effective for men with a 10-year CVD risk of >10 per cent and for women with a risk of >15 per cent (Circulation 2008; 117: 2875-83).
  • One recent study has recommended that in the absence of significant bleeding risks, aspirin should routinely be considered for all men and women without diabetes above the ages of 48 and 57 years, respectively, for primary CVD prevention (Heart 2008; 94: 1429-32).

Guidelines

  • The British Hypertension Society recommends primary prevention with aspirin for patients aged over 50 (whose BP is controlled) and who have target organ damage, diabetes or a 10-year cardiovascular risk of ≥20 per cent.
  • NHS Clinical Knowledge Summaries states that, overall, aspirin significantly red-uces the rate of cardiovascular events in people at risk of CVD, although trials have not shown a reduction in the rate of cardiovascular death. In addition, increasing evidence indicates aspirin is not effective in primary prevention of CVD in diabetic patients.
  • The National Prescribing Centre suggests that for primary prevention in type-2 diabetes, consideration for aspirin on an individual basis may be more appropriate.

Contributed by Dr Louise Newson, a GP in the West Midlands

Useful websites

Key points

  • Aspirin is increasingly being taken by healthy people.
  • Many people could be at unnecessary risk of GI haemorrhage.
  • Risks of aspirin are greater in older people.
  • Benefits with aspirin are greater for men than for women.
  • Aspirin appears to be less beneficial as primary prevention in diabetic patients.

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