Psychogenic and Organic Causes of Erectile Dysfunction: Part I
Joyce So, BSc
Co-author:
Dr. Sidney Radomski,
Urology, Toronto Western Hospital
In 1992, the National Institutes of Health Consensus Development Conference1 suggested the use of the term "erectile dysfunction" instead of "impotence" to describe one of the most common chronic medical problems affecting men over the age of 40. Erectile dysfunction is defined as the persistent inability to attain or maintain a sufficient penile erection for sexual intercourse in at least 50% of attempts. The prevalence and degree of erectile dysfunction increases with age, with men in their fifties being three times more likely to have this condition compared to men in their twenties.2 By the age of 65, 25% of men are afflicted with erectile dysfunction, a number which increases to 55% among 75-year-olds and 65% among 80-year-olds.2 However, erectile dysfunction should not be considered part of the normal aging process.
The multi-disciplinary, community-based Massachusetts Male Aging Study (MMAS)3 of men aged 40 to 70, conducted between 1987 and 1989, showed that 35% of the men reported moderate to complete erectile dysfunction, with 52% reporting at least some degree of dysfunction. They also reported a decrease in libido and the number of sexual thoughts, fewer nocturnal or morning erections, and less frequent intercourse with age. However, sexual satisfaction was unchanged, suggesting that age-related changes in sexual capacity were accommodated by altered expectations. By contrast, the National Ambulatory Medical Care Survey in 19964 showed that office visits for the treatment of erectile dysfunction had more than doubled since 1985, suggesting that the current aging population has higher expectations. In an increasingly healthier population of aging men, erectile dysfunction is becoming a major quality of life issue, affecting over 140 million men worldwide.5
Conditions associated with erectile dysfunction are listed in Table 1. Aging, as previously mentioned, is associated with an increased incidence of erectile dysfunction, but the condition should not be considered an inevitable consequence of aging. The MMAS3 showed that one-third of 70-year-old subjects reported no erectile dysfunction. However, aging is related to an increased incidence of co-morbidities that can cause erectile dysfunction.
Diabetes mellitus is associated with a particularly high rate of erectile dysfunction, affecting up to 95% of diabetic males over the age of 70.5 Some degree of erectile dysfunction is reported in 60% of diabetic males within five years of the onset of diabetes, and may even be the presenting symptom, pre-dating diabetes by years.6 The high incidence of erectile dysfunction in this population is related to the large and small vessel vascular disease and somatic and autonomic dysfunction associated with diabetes, and direct damage to the cavernosal tissue.
Another significant risk factor for erectile dysfunction is the use of medications that interfere with central neuro-endocrine or local neurovascular control of penile smooth muscle. Although the precise mechanisms are not clear, over 25% of erectile dysfunction is related to the adverse effects of medications.5,6,7 Drugs that are commonly associated with erectile dysfunction are listed in Table 2. Most commonly, erectile dysfunction is caused by anti-hypertensives, anti-depressants, other psychiatric disorder medications, and drugs used for treatment of cardiovascular disease. However, stopping the medications rarely results in the restoration of function and patients often require treatment for erectile dysfunction despite discontinuing use of these drugs. This emphasizes the importance of informing patients of potential side effects of medications, as well as the need for careful monitoring of sexual function on initiation and subsequent use of any of these medications. Dosage adjustments or substitution with another medication can often avoid the progression of erectile dysfunction with use of causative drugs.
Chronic substance use, such