BMJ  2005;331:161 (16 July), doi:10.1136/bmj.331.7509.161-a

Letter

Aspirin for everyone over 50?

Don't forget aspirin resistance

EDITOR—None of the authors in the debate for and against the prescribing of aspirin for those over 50 mentions the growing notion of aspirin resistance.^{1 2} This term is used to describe not only an absence of the expected pharmacological effects of aspirin on platelets but also poorer than expected clinical outcomes. Thus, in biochemical aspirin resistance the in vitro activation of platelets is persistent, and in clinical aspirin resistance patients taking aspirin have recurrent vascular events.

Several studies have now shown that a substantial minority of patients may have either total or partial aspirin resistance.³ Although these studies may have methodological differences, they suggest that between 5% and 55% of treated patients may have some degree of aspirin resistance. Recent data suggest that a substantial proportion of patients at a potentially greater risk of cardiovascular events than a normal population have aspirin resistance.⁴

Whether aspirin related side effects are less common in aspirin resistant patients is unknown. If they are not, then universal aspirin administration may be associated with an increase in side effects with no concurrent decrease in cardiovascular events.

Until these issues have been further investigated, it seems unwise to recommend aspirin for everyone over 50.

Norfolk and Norwich University Hospital NHS Trust, Norwich NR1 3SR ketan.dhatariya{at}nnuh.nhs.uk

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Competing interests: None declared.

References

1. Elwood P, Morgan M, Brown G, Pickering J. Aspirin for everyone older than 50?: FOR. BMJ 2005;330: 1440-1. (18 June.)[Free Full Text]
2. Baigent C. Aspirin for everyone older than 50?: AGAINST. BMJ 2005;330: 1442-3. (18 June.)[Free Full Text]
3. Sanderson S, Emery J, Baglin T, Kinmouth A. Aspirin resistance and its clinical implications. Ann Intern Med 2005;142: 370-80.[Abstract/Free Full Text]
4. Fateh-Moghadam S, Plöckinger U, Htun P, Reuter T, Ersel S, Gawaz M, et al. Prevalence of aspirin resistance in patients with type 2 diabetes. Acta Diabetol 2005;42: 99-103.[CrossRef][ISI][Medline]

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