Estimates of up to 40% of the adult population have varicose veins, with twice as many women affected as men. Up to 50% of these people experience pain. Varicose veins can start appearing in the second decade and become more common with age. By age 70, more than 70% of women are affected.

Heredity is the most dominant factor in the development of leg varicose veins. A family history of varicose and spider veins most likely will increase your chances of suffering from them in your lifetime.  Others who are vulnerable include those who develop a higher than normal abdominal/pelvic pressure that may occur as a result of obesity or during pregnancy.

Individuals who have had an injury to their leg or problems with blood clots in their veins can also develop varicose veins.

Hormonal changes during pregnancy, premenstruation and menopause may be a factor. Because elevated female hormones, particularly progesterone, tend to relax vein walls, women tend to develop more spider veins when they are pregnant, taking oral contraceptives, or on hormone replacement therapy.

There is some debate about whether prolonged standing actually causes varicose veins, although people who stand or sit for prolonged periods and on a regular basis can develop chronic venous congestion and resulting valvular incompetence. Certainly any venous condition will be aggravated by occupations requiring prolonged standing due to stasis of blood in the leg veins.