Impotence, or erectile dysfunction, is the inability to achieve or maintain an erection more than 20 percent of the time.
Erectile dysfunction affects millions of men.
Although in the past it was commonly believed to be due to psychological problems, it is now known that 80 to 90 percent of impotence is caused by physical problems, usually related to the blood supply of the penis. Many advances have occurred in both diagnosis and treatment of erectile dysfunction . According to the National Institutes of Health, erectile dysfunction is also a symptom in many disorders and diseases. It is estimated that nearly 5 percent of men become impotent by the age of 40, and 15 to 25 percent by the age of 65. Accurate risk factor identification and characterization are essential for prevention or treatment of erectile dysfunction.