Several studies have shown a lower incidence in Asian than in European populations, with recent data from national health insurance claim data in Taiwan showing an incidence of 16.5 per 100 000 per year, i.e., a ten-fold lower incidence than reported from Europe and the USA [
4]. Remarkably, the case fatality rate was similar if not higher than in the studies from Europe. Because many factors, including those related to the health care system, may cause differences in disease incidence and outcome between different geographic locations, studies that investigate individuals with different ethnic backgrounds living in the same country are highly interesting. One such study, from California, found slightly higher rates of venous thrombosis in blacks than in whites, and substantially lower (~5-fold reduction) in Asians [
5]. A similar study from New Zealand corroborated these results, with a four-fold lower incidence of venous thrombosis in Asians than in those from European descent [
6]. These data are compelling, but still there is some debate. Firstly, several studies have shown an equal rate of thrombosis after major risk factors such as surgery [
7,
8], although a recent study from Taiwan showed a low risk of thrombosis after knee arthroplasty, and therefore the authors concluded that thromboprophylactic regimens could be less aggressive in Asians than in Europeans [
9]. A report from Singapore showed that differences in medical practice do play a role, too: in 12 years time the proportion of patients with venous thrombosis per 10 000 hospital admissions had increased from 2.8 to 15.8 [
10]. Although in all likelihood the incidence in Asians is lower than in Europeans, it should be borne in mind that this is unlikely to be the same everywhere and for every ethnic group in Asia. Moreover, risk factors for thrombosis seem to be the same in Asians as in Europeans, with the notable exception of factor V Leiden and prothrombin 20210A which are very rare in Asia. The absence of these two risk factors cannot explain the difference in incidences, since together they explain about 15–20 % of all thrombotic events in Europeans. The reason for the different rates between Asians and Europeans is unknown, although the persistence of the difference in ethnic groups in the United States and New-Zealand suggests a genetic cause.
The causes of venous thrombosis are genetic, acquired, behavioral and combinations of disease, and will be briefly discussed below. Table
1 list the main risk factors for venous thrombosis. Generally, and according to Virchow, risk factors can be related to stasis, hypercoagulability and changes in the vessel wall, of which the last category is more a risk factor for arterial disease than for venous thrombosis.
Table 1
Causes of venous thrombosis
Age | Oral contraceptives | Obesity | Non-0 blood group | High FVIII |
Major surgery | Postmenopausal hormones | Long-haul travel | Antithrombin deficiency | High VWF |
Neurosurgery | In vitro fertilization | Smoking | Protein C deficiency | High FIX |
Orthopaedic surgery | Chemotherapy | No alcohol | Protein S deficiency | High FXI |
Prostatectomy | Psychotropic drugs | No exercise | Factor V Leiden (rs6025) | High prothrombin |
Malignancy | Thalidomide | Exercise (elderly) | Prothrombin 20210A (rs1799963) | dysfibrinogenaemia |
Trauma | Corticosteroids | Coffee | fibrinogen 10034 T (rs2066865) | Low TFPI |
Prolonged bed rest | | Strenuous work (arm thrombosis) | factor XIII val34leu (rs5985) | High PCI |
Central venous catheter | | | SERPINC1 (rs2227589) | High fibrinogen |
Plaster cast | | | FXI (rs2289252) | High TAFI |
Myeoloproliferative disease | | | FXI (rs2036914) | Hypofibrinolysis |
Heparin induced Thrombocytopenia | | | GP6 (rs1613662) | Hyperhomocysteinaemia |
Hyperthyroid disease | | | FV (rs4524) | Hypercysteinaemia |
Cushing syndrome | | | HIVEP1 (rs169713) | |
Arthroscopy | | | TSPAN15 (rs78707713) | |
Lupus anticoagulant | | | SLC44A2 (rs2288904) | |
| | | ORM1 (rs150611042) | |