Risk factors that increase your likelihood of developing DVT are similar to those for other vein diseases. These include: Age (being over 60). Heredity (whether a family member has had it). Obesity. Smoking. Pregnancy, and the use of oral contraceptives or hormone replacement therapy (HRT). Another risk factor for DVT is reduced mobility, caused by long periods of hospitalisation or sitting in one position for hours. Such as long-distance travel. DVT can also be triggered by injuries to blood vessels incurred as the result of trauma or during surgery. The question of whether having varicose veins is a significant risk factor for DVT is more controversial. Because a clear cause-and-effect relationship has not been firmly established. However, in a study reported in the German journal VASA, researchers found that 5.6% of patients with varicose veins developed DVT. Compared to 0.9% of the control group without varicose veins. They also found that those with varicose veins who also had a history of previous venous thromboembolism or a recent hospital discharge were even more at risk. For more information see our article on how to Prevent Varicose Veins during Long Haul Travel.