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Bleeding near brain is linked to increased use of anti-clotting drugs, study finds

BMJ 2017; 356 doi: (Published 01 March 2017) Cite this as: BMJ 2017;356:j1044
  1. Jacqui Wise
  1. London

The risk of subdural haematoma is associated with antithrombotic drug use, particularly a vitamin K antagonist, a large Danish study has found.1

Although use of antithrombotic drugs has long been recognised as a risk factor for subdural haematoma, previous studies were either based exclusively on patients with subdural haematoma and no comparison group or focused exclusively on patients treated with an anticoagulant.

The researchers used a Danish registry to identify 10 010 patients with a first ever subdural haematoma from 2000 to 2015. The patients were matched to 400 380 people from the general population. Among the patients with subdural haematoma, 47% were taking antithrombotic medicine.

The study found that current use of low dose aspirin was associated with slightly increased odds of subdural haematoma (adjusted odds ratio 1.24 (95% confidence interval 1.15 to 1.33)). Clopidogrel and a direct oral anticoagulant were associated with moderately higher odds of haematoma (1.87 (1.57 to 2.24) and 1.73 (1.31 to 2.28), respectively). The use of a vitamin K antagonist, such as warfarin, was associated with higher odds of subdural haematoma (3.69 (3.38 to 4.03)).

Concurrent use of more than one antithrombotic drug was related to substantially higher odds of subdural haematoma, with the exception of low dose aspirin combined with dipyridamole, which was similar to use of low dose aspirin alone. The odds of subdural haematoma were highest when a vitamin K antagonist was used concurrently with an antiplatelet drug. The adjusted odds ratio with low dose aspirin and a vitamin K antagonist was 4.00 (3.40 to 4.70) and with clopidogrel and a vitamin K antagonist was 7.93 (4.49 to 14.02).

Antithrombotic drug use was associated with higher relative risks of subdural haematoma in women than in men. Fatal subdural haematoma was more strongly associated with antithrombotic drug use than non-fatal subdural haematoma.

The prevalence of antithrombotic drug use increased in the general population from the year 2000 to 2015, as did overall subdural haematoma incidence, the study found.

The authors concluded, “The present data add one more piece of evidence to the complex risk-benefit equation of antithrombotic drug use. It is known that these drugs result in net benefits overall in patients with clear therapeutic indications.”


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