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Erectile Dysfunction: Overview and Risk Factors

Erectile dysfunction (ED) is the inability to acquire or sustain an erection of sufficient rigidity for sexual intercourse. The condition affects 15 million to 30 million men in the United States. Most cases of ED consist of impotence, the inability to achieve or sustain an erection during attempted sexual intercourse more than 75% of the time. Other disorders include abnormal curvature of the penis during erection (Peyronie's disease), priapism, decreased libido, inability to ejaculate, and premature ejaculation. Any disorder that impairs blood flow to the penis (eg, atherosclerosis) or causes injury to the penile nerves, smooth muscle, or fibrous tissue has the potential to cause ED. At least 25% of cases are related to reversible etiologies, including psychogenic causes, endocrine abnormalities, and drugs (eg, sympathetic blockers, antidepressants, and antihypertensives).

Changes in erectile function are common and normal with age. Erections may take longer to develop, be less rigid, or require more direct stimulation. Orgasms may be less intense, the volume of ejaculate decreases, and the refractory period increases. Further, emotional disturbances may result in erectile difficulties in the absence of organic pathology. However, ED is not an inevitable consequence of aging. Most cases are treatable, and occasional episodes are considered normal.

Risk Factors

Age. Erectile dysfunction is most common in men older than 65. About 5% of 40–year–old men and 15% to 25% of 65–year–old men experience some degree of erectile dysfunction.

Vascular disease. Atherosclerosis causes a reduction in blood flow and accounts for 50% to 60% of cases.

Diabetes mellitus. At least half of patients with long–standing diabetes experience ED, due to damage of small blood vessels and nerves.

Neurologic conditions. Several neurologic conditions result in ED, including spinal cord and brain injuries, multiple sclerosis, Parkinson's disease, and Alzheimer's disease.

Hormone imbalance. Testosterone deficiency (eg, pituitary tumor, and kidney or liver disease) can result in loss of libido and erectile difficulties.

Surgery. Colon, prostate, bladder, and rectum surgery may damage nerves and blood vessels involved in erection. Nerve–sparing techniques decrease impotence incidence to around 50%.

Radiation therapy. Radiation treatment for prostate or bladder cancer may cause ED.

Medications. More than 200 commonly prescribed drugs result in ED as a prominent side effect. These include beta–blockers, thiazides, antihistamines, antidepressants, tranquilizers, and appetite suppressants.

Substance abuse. Excessive use of alcohol, tobacco, marijuana, 3,4–methylenedioxymethamphetamine (MDMA, better–known as Ecstasy), and other recreational drugs can cause ED, which may be irreversible in some cases. For example, excessive tobacco use can permanently damage penile arteries.

Obesity. Excess body fat weight contributes to ED by increasing estrogen activity and aggravating diabetes and lipid disorders.


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