Risk factors for ED have been delineated in large prospective studies, such as Massachusetts Male Aging Study (MMAS), Boston Area Community Health Survey (BACHS), and Health Professionals Follow-up Study (HPFS). The MMAS study reported on males between ages 40 and 70 years and found that erectile function declined precipitously with age. Overall, the study found that 52% of men within this age range suffered from some degree of ED. Diabetes, heart disease, and hypertension increased the risk of ED significantly in this study.

Erectile dysfunction was studied in men aged 45–70 years with a 14-year follow-up in the HPFS. Excluding men who developed prostate cancer, the relative risk (RR) of development of ED as per self-assessment was 1.5 for current smokers and 1.9 for obese men. In contrast, moderate exercise decreased the risk of ED. Interestingly, these risk factors produced greater effect in men 55 years or younger.

The BACHS was created specifically to assess urologic symptoms in a diverse cohort.

  • This study found a dose-response effect of tobacco cigarettes on ED, although there was not a significant increase in the odds of developing ED until over 20 pack-years of the habit.
  • They also found that low socioeconomic status, independent of other risk factors, including race, was a risk factor for ED.

Erectile Physiology A successful male penile erection requires two processes. Cavernosal artery smooth muscle relaxation and increased venous outflow resistance. In order to sustain an erection one must achieve and maintain a high arterial inflow and a low venous outflow. Cavernosal arterial smooth muscle relaxation is an active process and the initial event of an erection. viagra tablets online

1. Smooth muscle relaxation leads to arterial dilation which results in increased penile blood flow that in turn causes radial and longitudinal cavernosal expansion. This process is mediated by nitric oxide released through stimulation of nonadrenergic, noncholinergic nerves (NANC).

2. Nitric oxide binds to smooth muscle cells stimulating the production of cyclic GMP, which then decreases intracellular calcium and causes relaxation. Cyclic AMP, a second minor messenger, acts in a similar manner to decrease intracellular calcium and causes muscle relaxation.

Venous outflow resistance, in contrast to arterial smooth muscle relaxation, is a passive process. As the cavernosal tissues engorge and expand, they compress the subtunical venous sinuses and cause the outflow resistance necessary to maintain an erection.