All About Impotence

Impotence is a consistent inability to sustain an erection sufficient for sexual intercourse. Medical professionals often use the term "erectile dysfunction" to describe this disorder and to differentiate it from other problems that interfere with sexual intercourse, such as lack of sexual desire and problems with ejaculation and orgasm. This fact sheet focuses on impotence defined as erectile dysfunction.

Impotence can be a total inability to achieve erection, an inconsistent ability to do so, or a tendency to sustain only brief erections. These variations make defining impotence and estimating its incidence difficult. Experts believe impotence affects between 10 and 15 million American men. In 1985, the National Ambulatory Medical Care Survey counted 525,000 doctor-office visits for erectile dysfunction.

Impotence usually has a physical cause, such as disease, injury, or drug side-effects. Any disorder that impairs blood flow in the penis has the potential to cause impotence. Incidence rises with age: about 5 percent of men at the age of 40 and between 15 and 25 percent of men at the age of 65 experience impotence. Yet, it is not an inevitable part of aging.

Impotence is treatable in all age groups, and awareness of this fact has been growing. More men have been seeking help and returning to near-normal sexual activity because of improved, successful treatments for impotence. Urologists, who specialize in problems of the urinary tract, have traditionally treated impotence -- especially complications of impotence.

How Does an Erection Occur?

The penis contains two chambers, called the corpora cavernosa, which run the length of the organ (see figure 1). A spongy tissue fills the chambers. The corpora cavernosa are surrounded by a membrane, called the tunica albuginea. The spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and arteries. The urethra, which is the channel for urine and ejaculate, runs along the underside of the corpora cavernosa.

Erection begins with sensory and mental stimulation. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the open spaces. The blood creates pressure in the corpora cavernosa, making the penis expand. The tunica albuginea helps to trap the blood in the corpora cavernosa, thereby sustaining erection. Erection is reversed when muscles in the penis contract, stopping the inflow of blood and opening outflow channels.

What Causes Impotence?

Since an erection requires a sequence of events, impotence can occur when any of the events is disrupted. The sequence includes nerve impulses in the brain, spinal column, and area of the penis, and response in muscles, fibrous tissues, veins, and arteries in and near the corpora cavernosa.

Damage to arteries, smooth muscles, and fibrous tissues, often as a result of disease, is the most common cause of impotence. Diseases -- including diabetes, kidney disease, chronic alcoholism, multiple sclerosis, atherosclerosis, and vascular disease -- account for about 70 percent of cases of impotence. Between 35 and 50 percent of men with diabetes experience impotence.