Thromboses occur in approximately 160,000 patients per year in Germany. The likelihood increases with age, reaching about 1% per year from the age of 70. The most common location is in the thigh and knee areas. Deep vein thromboses can serve as the starting point for a dangerous pulmonary embolism. The risk depends on the extent and location of the thrombus and ranges between 2.5% and 9%. Three main factors primarily contribute to the development of thrombosis. When multiple factors are present, the risk increases exponentially:
- Damage to the vessel wall, e.g., due to atherosclerosis or injuries
- Stagnant blood flow, e.g., prolonged bed rest, heart failure, or long-distance travel in cramped airplane seats
- Increased blood clotting tendency, e.g., oral contraceptives, post-surgery, cancer, or infections
These are collectively referred to as the Virchow Triad. However, the most significant risk factor is a family history of thromboembolism, which increases the risk by 250 times (compared to a 2- to 4-fold increase for long-distance travel).