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Erectile Dysfunction: Overview and Risk Factors

Erectile dysfunction (ED) is the inability to acquire or sustain an erection sufficient for sexual intercourse. It is a common condition that affects 15 million to 30 million men in the United States.

ED can be caused by many medical disorders, including abnormal curvature of the penis during erection (Peyronie's disease) and sustained erections that decrease the flow of oxygen to cells of the penis (priapism). Further, any disorder that impairs blood flow to the penis (e.g., atherosclerosis) or causes injury to the penis has the potential to cause ED. Many cases of ED are permanent, but at least 25 percent of cases are reversible, especially cases caused by decreased sexual desire, emotional factors, hormonal abnormalities, or drugs (e.g., 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, and orgasms may be less intense. 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 percent of 40–year–old men and 15 to 25 percent of 65–year–old men experience some degree of erectile dysfunction.
  • Vascular disease: Atherosclerosis causes a reduction in blood flow to the penis and accounts for 50 to 60 percent of cases.
  • Diabetes mellitus: At least half of individuals 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 (e.g., brain tumor, kidney or liver disease) can result in loss of sexual interest and erectile difficulties.
  • Surgery: Colon, prostate, bladder, and rectum surgery may damage nerves and blood vessels involved in erection.
  • Radiation therapy: Radiation treatment for prostate or bladder cancer may cause ED.
  • Medications: More than 200 commonly prescribed drugs can cause ED as a side effect. These include beta–blockers, diuretics, antihistamines, antidepressants, tranquilizers, and appetite suppressants.
  • Substance abuse: Excessive use of alcohol, tobacco, marijuana, 3,4 methylenedioxymethamphetamine (“ecstasy”), and other recreational drugs can cause ED, which may be irreversible in some cases.
  • Obesity: Excess body fat weight contributes to ED by increasing estrogen activity and worsening diabetes and high cholesterol.


Erectile Dysfunction: Diagnosis and Treatment >>