Many people attribute varicose veins or "spider veins" to age. Women often find them embarrassing. But, they can be painful, and even lead to health risks if left untreated. It's estimated that 40 percent of adult women have varicose veins and 20 percent of men also show symptoms of venous insufficiency. The cause of venous insufficiency is a degeneration of the valves in the veins that carry blood back to the heart and lungs. When the valves fail to work properly, blood can pool in the veins, causing them to dilate and become visible. Genetics and age play a role in the condition, but so does gender. Females more commonly show signs of the disease than men and pregnancy is thought to be a contributor.