Epidemiology and risk factors. Male erectile dysfunction

Male erectile dysfunction has been defined as the persistent inability to attain and maintain an erection

sufficient to permit satisfactory sexual performance. Although erectile dysfunctionis a benign disorder, it is related to physical
and psychosocial health, and has a significant impact on the quality of life of both sufferers and their partners
and families.
Recent epidemiological data have shown a high prevalence and incidence of erectile dysfunctionworldwide. The first
large-scale, community-based study, Massachusetts Male Aging Study (MMAS), reported a combined
prevalence of 52% erectile dysfunction in non-institutionalized 40 to 70-year-old men in the Boston area (2). In this study, the
individual prevalences were 17.2, 25.2 and 9.6 for minimal, moderate and complete erectile dysfunction, respectively. In the
Cologne study (men 30-80 year-old), the prevalence of ED was 19.2%, with a steep age-related increase 
(2.3-53.4%) (3), while the prevalence of sexual dysfunctions (not specific ED) in the National Health and Social
Life Survey was 31% (4). Analysis of the longitudinal results from the MMAS study estimated that the incidence
of ED was 26 new cases per 1000 men annually (5), while the incidence rates (new cases per 1000 men annually)
of ED in a Brazilian (6) and in a Dutch (7) study were estimated at 65.6 (mean follow-up 2 years) and 19.2 (mean
follow-up 4.2 years), respectively. Differences in these studies can be explained by the methodology design of
the different surveys, the age and the socio-economic status of the populations studied.
Erection is a neurovascular phenomenon under hormonal control. It includes arterial dilatation,
trabecular smooth muscle relaxation and activation of the corporeal veno-occlusive mechanism (8). Several risk
factors have been identified based on the knowledge of physiology or erection. Actually, it became clear that
ED shares common risk factors with cardiovascular disease as the lack of exercise, obesity, smoking,
hypercholesterolaemia and the metabolic syndrome. Several life-style risk factors can be modified. In the
MMAS, men who initiated physical activity in midlife had a 70% reduced risk for ED relative to those who
remained sedentary, while in its longitudinal results, regular exercising showed a significantly lower incidence of
ED over an 8-year follow up period (9). A multicentre, randomized, open-label study compared 2 years of
intensive exercise and weight loss with an educational control in obese men with moderate ED (10). 
Significant improvements in body mass index (BMI) and physical activity scores, as well as in erectile function
were observed in the lifestyle intervention group, while those changes were highly correlated with both weight
loss and activity levels. However, it should be emphasized that controlled prospective studies are necessary to
determine the effects of exercise or other lifestyle changes in prevention or treatment of ED.