Epidemiological studies conducted in France and Sweden allow accurate estimates of the magnitude of the problem of VTE in Europe. The EPI-GETBO study examined the occurrence of thrombosis in a population in western France (n=342,000) for 1 year . The overall incidence of VTE was 183 per 100,000 persons, with DVT accounting for 124 per 100,000 persons and PE for 60 per 100,000 persons. Figures obtained by reviewing all positive phlebography tests recorded in Malmo, Sweden, during 1987 were very similar, with 160 DVT cases per 100,000 persons .
In the USA, a study retrospectively reviewed the complete medical records from a defined population of persons who resided within Olmsted County, Minnesota. Of these persons, 2218 had a DVT or PE during the 25-year period from 1966 through 1990. The overall mean age- and sex-adjusted annual incidence of VTE was 117 per 100,000 persons (DVT 48 per 100,000 persons and PE 69 per 100,000 persons) .
Most epidemiological studies that examine risk and attributable risk for thrombosis, group DVT and PE together, and report on VTE. The risk of VTE is markedly higher in subgroups of people. A population-based study in the USA found that hospital, nursing home, or other chronic care facility confinement was an independent risk factor for VTE, associated with an eight-fold increase in risk, and this risk was substantially increased if accompanied by surgery, rising to 22-fold . Trauma was associated with a 13-fold increase and malignancy with a four-fold increase in risk.
Further analysis of the population-based dataset in the USA showed that factors related to current or recent hospitalisation or nursing home residence independently accounted for about 50% of the attributable risk of VTE. Other known risk factors for VTE accounted for 25% of attributable risk, and the remaining 25% are described as idiopathic . DVT rates in hospitalised patients are shown in the table below.
|Patient group||Prevalence of DVT|
|Major gynaecological surgery||15–40%|
|Major urological surgery||15–40%|
|Hip or knee replacement surgery||40–60%|
|Intensive care medicine||10–80%|
Table: frequency of DVT in surgical and medical patients without prophylaxis; rates are based on objective diagnostic screening for asymptomatic DVT in patients not receiving thromboprophylaxis .
Post thrombotic syndrome (PTS) is an important chronic consequence of DVT. PTS develops in one-fifth to one-half of patients with DVT  even when appropriate anticoagulant therapy is used. Based on its high incidence and prevalence, PTS is the most frequent complication of DVT. A total of 5–10% of patients develops severe PTS, which can manifest as venous ulcers . PTS has an adverse impact on quality of life as well as significant socioeconomic consequences. Investigation of the relationship between the quality of anticoagulant treatment after DVT and the risk of PTS, showed that patients who spent more than 50% of their time inadequately anticoagulated were at higher risk of developing PTS . The provision of prompt and adequate oral anticoagulation of appropriate intensity and duration for the initial treatment of DVT is, therefore, important in the prevention of PTS . Recurrent VTE is an important risk factor for PTS, suggesting improved anticoagulation has the potential to reduce the risk of PTS .