UP TO a quarter of people could be resistant to the anti-clotting effects of aspirin, and for some the cause is genetic. Polish researchers have identified a variation in a gene for a molecule on the surface of blood platelets that helps make them sticky. This variation is present in up to 25 per cent of Caucasians, and these people鈥檚 sensitivity to aspirin鈥檚 anti-clotting effects is reduced by between 30 and 60 per cent.
Daily aspirin is recommended for virtually everyone with a high risk of cardiovascular disease. 鈥淏ut it is now thought that somewhere between 15 and 25 per cent of people do not in fact respond well to the anti-clotting effects of aspirin,鈥� says Andrew Szczeklik of Jagiellonian University in Cracow, Poland, who presented his findings at a meeting of the International Society on Thrombosis and Haemostasis in Sydney, Australia, last week.
The health implications are unclear, but a previous study of 326 cardiovascular patients on aspirin did find an increased risk of stroke and heart attack in aspirin-resistant people (Journal of the American College of Cardiology, vol 41, p 961).
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This suggests lives might be saved if such people were identified and given alternative drugs such as clopidogrel, which inhibits clotting through a different mechanism.
High blood cholesterol is also thought to reduce aspirin鈥檚 anticoagulant effect.
