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.
- 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.
- The evaluation begins with a medical history and a physical examination. A careful medical and sexual history is essential for diagnosis. Sexual history should include onset of symptoms, ability to achieve spontaneous erections (i.e., morning erections), and risk factors for impotence (e.g., cigarette smoking, diabetes mellitus, hypertension, drug abuse, and obesity). A psychiatric interview and questionnaire may reveal psychological factors, such as depression and anxiety. In some cases, it may be helpful to interview the patient's sexual partner.
- Blood tests may be necessary, including cholesterol level, thyroid tests, and testosterone level.
- In some cases, overnight testing (nocturnal penile tumescence testing) can be used to measure the number and strength of erections during sleep, which can rule out psychological causes and can help identify men who might benefit from corrective surgery.
- In addition, ultrasound or other tests of the penile arteries may be recommended.
Treatment is aimed at restoring the capacity to acquire and sustain erections and reactivating sexual desire.
- Smoking cessation is important if the patient smokes.
- The most commonly used medications are the phosphodiesterase-5 inhibitors (e.g., sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis)). However, these medications should not be used in men taking nitrate medications for heart disease.
- Hormonal therapy with testosterone may be effective, but long-term use carries risks, so it is only used in a small number of individuals with documented medical disorders.
- Treatment of associated psychiatric disorders may improve sexual functioning. Between 20 and 50 percent of men with impotence have symptoms of depression, which may contribute to ED. Self-esteem may also suffer as a result. Individual or couples psychotherapy may be a helpful part of treatment.
- In some cases, penile injections, vacuum devices, or surgery may be beneficial.
Erectile Dysfunction: Nutritional Considerations
Erectile dysfunction is often the result of vascular disease. Risk factors for cardiovascular disease are commonly found in affected men. These include obesity, elevated cholesterol and triglyceride levels, smoking, inactivity, and diabetes. Moreover, impotence should be viewed as a sign of artery disease. It means that other cardiovascular problems may manifest in the future, and that diet and lifestyle changes to help prevent these problems are essential.
- Dietary changes to lower cholesterol: Although the evidence on nutritional treatment is limited, interventions that reduce cardiovascular risk factors or improve blood vessel functioning (diet, exercise, and certain botanical agents) may improve the disorder. In one study, a low-fat, low-cholesterol diet combined with exercise resulted in normal sexual function in 31 percent of impotent men, compared with only 5 percent of patients who did not follow these recommendations.
More importantly, dietary changes can improve the health of the cardiovascular system generally, reducing the risk of heart problems and other conditions for which ED is a warning sign. The most effective diet for controlling cholesterol and improving arterial health is a low-fat, vegan diet.
See Coronary Heart Disease chapter and Hyperlipidemia chapter for dietary factors to prevent or treat cardiovascular disease.
- Dietary supplements: Dietary supplements are not a substitute for a healthful diet and lifestyle. Nonetheless, two dietary supplements, L-arginine and ginseng, appear to be effective in treating ED in clinical trials.
L-arginine was shown to be effective in 30 to 40 percent of patients taking 3 to 5 grams per day, compared with a placebo. Combinations of arginine and yohimbine increase the response to more than 90 percent. However, not all trials of L-arginine have been adequately controlled, and further study is necessary.
Controlled clinical studies of Panax ginseng have found that patients treated with ginseng had significantly improved symptoms than those who received placebo. The studies also found that the number of patients treated with ginseng who experienced improved erections was double that of placebo-treated patients. Additional controlled clinical studies are needed to establish a role for ginseng in ED treatment.
Dietary supplements should be used only under medical supervision due to the possibility of medication interactions.