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expert reaction to research on anti-clotting drugs and bleeding near the brain

Published in JAMA scientists investigated the association between use of antithrombotic drugs and subdural hematoma risk.


Prof. Alun Hughes, Professor of Cardiovascular Physiology and Pharmacology at UCL, said:

“This is a good quality study of a relevant sample of sufficient size to draw robust conclusions. The findings are consistent with what is known regarding the risks of bleeding in people taking anti-clotting drugs, but provide more detail concerning the risk of a rare, but serious bleeding complication, subdural hematoma. It convincingly shows that this complication has increased over the last decade in Denmark in parallel with an increased rate of prescription of such drugs and that this bleeding complication is commoner in people taking ‘stronger’ anticoagulant therapy. The study cannot conclusively prove that the increased prescription rate caused the increased rate of subdural hematoma, but it is a credible proposition.

“The study does have some limitations – such as missed cases and limited information regarding alcohol consumption and monitoring of anti-coagulant drug action. These deficiencies are unlikely to substantially undermine the study.

“The study is relevant as this type of drug is widely used in older people – more than 1 million people are prescribed anti-coagulant drugs in UK.  But it is important to note that this complication is rare – in the study there was only approximately 1 event per 10,000 person years in 2000 and 2 events per 10,000 person years in 2015. Even if all of the difference between 2000 and 2015 were attributable to increased use of anticoagulants then it would be a small effect (1 event in 10,000 people treated for 1 year).

“Current evidence convincingly shows that when used appropriately the benefits of anti-clotting drugs outweigh the risks and I don’t think that this study changes that conclusion. The findings should not be a source of alarm to people taking these drugs to prevent strokes or other clotting complications.”


Dr Mike Knapton, Associate Medical Director at the British Heart Foundation, said:

“These are commonly prescribed drugs and their use is increasing. They are usually given to patients to prevent blood clotting, often following heart surgery.

“The risk is that because these drugs work by thinning the blood, they carry an increased chance of haemorrhage which is exactly what this research shows. However, when considering the link between the drugs and bleeding, the researchers accounted for most variables except alcohol intake, which can increase risk of bleeding near the brain for these patients.

“No medication is without the risk of side effects. The findings of this large study further demonstrate just how important it is for anyone offered one of these drugs to be made aware of the benefits and the risks so that they can make an informed choice about their treatment. If you have any concerns about your medication you should speak with your GP.”


* ‘Association of Antithrombotic Drug Use With Subdural Hematoma Risk’ by David Gaist et al. will be published in JAMA on Tuesday 28 February.


Declared interests

None declared

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