The etiology of ED is usually multifactorial. Organic, physiologic, endocrine, and psychogenic factors are involved in the ability to obtain and maintain erections. In general, ED is divided into organic and psychogenic impotence, but most men with organic etiologies usually have an associated psychogenic component. Almost any disease may affect erectile function by altering the nervous, vascular, or hormonal systems. Various diseases may produce changes in the smooth muscle tissue of the corpora cavernosa or influence the patient's psychologic mood and behavior. Pure psychogenic ED is an uncommon disorder, although most ED was once attributed to psychological factors.
Diabetes is a well-recognized risk factor, with up to 50% of men with diabetes experiencing ED. The etiology of ED in diabetic men probably involves both vascular and neurogenic mechanisms. Evidence indicates that establishing good glycemic control can minimize this risk.
Cigarette smoking has been shown to be an independent risk factor. Studies have shown that the risk of developing ED increased by a factor of 2 in men who smoke.
Mental health disorders, particularly depression, are likely to affect sexual performance. Other associated factors, both cognitive and behavioral, may contribute. Also, ED alone can induce depression. The new oral agents have been shown to be effective for men who develop depression following prostatectomy.
Cosgrove et al have reported a higher rate of sexual dysfunction in veterans with posttraumatic stress syndrome than in those veterans who did not develop this problem. The domains on the IIEF questionnaire that demonstrated the most change included overall sexual satisfaction and erectile function. This study suggests that regardless of etiology, men with posttraumatic stress syndrome should be evaluated and treated if they have sexual dysfunction.
A sedentary lifestyle is also a contributing factor to ED. Exercise has a beneficial effect on the cardiovascular system, and some data from the MMAS study indicate that men who exercise regularly have a lower risk of ED. However, Goldstein et al reported an increased risk of ED in men who rode a bicycle for long periods. Therefore, the type of exercise may be important.