The Massachusetts Male Aging Study (MMAS) is a prospective observational longitudinal study of health in randomly selected men. It investigates the effects of aging on male sexual health, among other domains. This landmark study reported a combined prevalence of minimal, moderate, and complete ED of no less than 52 % in US men. The prevalence of complete ED tripled from 5 to 15 % between subject ages 40 and 70 years. In the European Male Ageing Study (EMAS), a collaborative effort of eight European centers investigating the effects of aging on general and sexual health in a male population aged 40–79 with a mean age of 60 years old, about one-third of the entire EMAS sample reported ED. The prevalence of ED was higher in the older age groups, peaking at 64 % in men over 70 years of age. However, it appears from the results of the EMAS study that although patients in older age groups are more frequently affected by the disease, they tend to be less bothered with the presence of ED. With the rapidly expanding aging population and the increase in life expectancy, an increase in the prevalence of ED is expected in the years to come. It is estimated that in 10 years, about one in ten men of the worldwide population will be older than 65 years of age. By then, the number of men suffering from ED will reach 322 million worldwide.

While ED does not pose direct threat to physical health, it can have dramatic effects on personal sense of well-being and has a significant impact on the quality of life of patients and their sexual partners. Besides this impact, ED is also an independent predictor of cardiovascular morbidity and mortality. It is frequently postulated that “the penis is the antenna of the heart,” and as such, the complaint of ED should always trigger further questioning and investigation to identify underlying cardiovascular disease or other comorbidities. These other comorbidities are often related to the cardiovascular risk profile and include diabetes mellitus, metabolic syndrome, and smoking. Iatrogenic ED is not uncommon and can be the result of pelvic surgical procedures or the use of various medications. Besides these underlying issues, it is of particular importance to the readers of this book to be aware that community-based, preclinical and clinical data demonstrate a strong and consistent association between LUTS and ED, suggesting that elderly men with LUTS should be evaluated for ED and vice versa. Therefore ED merits consideration from both the primary care physician and the specialist as an important health concern in se and as a potential sentinel for serious health conditions. In this chapter we will discuss the pathophysiology of erectile dysfunction in men and the essentials in ED evaluation and ED treatment.

Sex drive is the initiator of penile erection, and therefore, intact libido, mood, and psychosocial circumstances are capital to normal erectile function. Penile erection requires neural transmission of pro-erectile impulses, being the efficacious delivery of the neurotransmitter nitric oxide (NO) to the smooth muscle in the corpus cavernosum. Furthermore, an intact arterial blood supply is key to supply the cavernous erectile tissue with oxygenated blood. The end organ, the corpus cavernosum, should be in good health, containing healthy smooth muscle and being elastic to successfully expand and compress the subtunical venous plexus during the rigid phase of erection. Lastly, hormonal balance should be in order as testosterone is a key mediator of libido but also keeps the peripheral effectors, such as cavernous smooth muscle and cavernous nerves, in good shape. ED can develop as result of a failure in one of these systems or, as is commonly the case, a multilevel failure. ED is typically defined as neurogenic, vasculogenic, hormonal, anatomical/structural, drug induced, or psychogenic. A summary of prevalent causes of ED is given in Table 12.1.