Risk Factors of Deep Vein Thrombosis

Deep vein thrombosis is a clinical challenge for doctors of all disciplines. It can complicate the course of a disease but might also be encountered in the absence of precipitating disorders. Thrombosis can take place in any section of the venous system, but arises most frequently in the deep veins of the leg. Long-term morbidity due to post-thrombotic syndrome is common and can be substantial. The major concern, however, is embolisation of the thrombus to the lung, which can be fatal. Deep vein thrombosis is highly prevalent and poses a burden on health economy. The disorder and its sequelae are also among the best examples of preventable diseases. Relevant data for the frequency of deep vein thrombosis derive from large community-based studies because they mainly reflect symptomatic rather than asymptomatic disease. In a systematic review, the incidence of first deep vein thrombosis in the general population was 0·5 per 1000 person-years.1 The disorder is rare in children younger than 15 years,2,3 but its frequency increases with age, with incidence per 1000 person-years of 1·8 at age 65–69 years and 3·1 at age 85–89 years.4 Two-thirds of first-time episodes of deep vein thrombosis are caused by risk factors, including surgery, cancer, immobilisation, or admission for other reasons.5,6 Risk for first deep vein thrombosis seems to be slightly higher in men than in women.6,9 In a populationbased cohort study, the age-adjusted incidence of first venous thromboembolism was 1·3 per 1000 person-years in men and 1·1 per 1000 person-years in women.2 It is noteworthy that the risk for recurrence of this disorder is higher in men than in women.6,10