Men have a 50% higher relative risk of suffering from recurrent blood clots after a first episode than women, according to an article in this week's issue of The Lancet. The baseline frequency of recurrent blood clots is 25% after five years.
Dr Simon McRae from the Department of Haematology (Queen Elizabeth Hospital, Woodville, South Australia, Australia) and his colleagues from the Department of Medicine, McMaster University (Hamilton, Ontario, Canada) did a meta-analysis of studies involving both men and women who were being treated for either deep vein thrombosis or pulmonary embolism (in which a clot detaches from a deep vein and lodges in the lung). They looked at rates of recurrence of blood clots in patients after they had stopped taking preventative anticoagulant (blood-thinning) medication.
A total of 5416 patients were enrolled in 15 eligible studies, 50% were men and 50% women. There were 816 recurrent blood clots, of which 523 (64%) were in men and 293 (36%) were in women.
The cause of heightened risk in men is unclear, but the authors state it could be attributable to differences in age, body mass index, or inherited susceptibility to blood clots. Dr Simon McRae writes: "further prospective studies are needed before a firm recommendation can be made to incorporate patient sex into decision making on duration of anticoagulant treatment in individual patients."