Problems related to chronic venous disease such as varicose veins are extremely common in the general population of the western world. Various studies have demonstrated that it occurs in up to 50% of men and 60% of women. More severe venous problems such as venous ulceration are less common, affecting 0.3% of the adult population. Approximately 1 person in 20 will develop a Deep Vein Thrombosis (DVT) in the course of his or her lifetime. By far the greatest incidence of DVT is seen in immobile hospitalised patients, particularly those with cancer or in patients following orthopaedic surgery.
Risk factors for venous diseases are more difficult to separate out. The incidence of venous disease increases with age and pregnancy. Prolonged standing has been proposed, and obesity has been suggested as a risk factor in women, but appears to be an aggravating factor rather than a primary cause. One of the most significant predisposing factors is familial history with a very high incidence passed on from mother to daughter.
The cause of DVT is related to one or more of the three critical factors known as "Virchow's Triad, i.e., abnormal or sluggish blood flow, trauma the the inner lining of the vein, and genetic abnormalities affecting the blood itself that cause it to clot more easily.