Erectile Dysfunction Disease Background

Introduction

Erectile dysfunction (ED) is the inability to attain and maintain an erection sufficient for satisfactory sexual performance.

Increasing evidence has shown that erectile dysfunction can be an early manifestation of coronary artery and peripheral vascular disease.

Epidemiology

The prevalence of erectile dysfunction increases with age as sexual activity decreases. In 1995, it was estimated that as many as 150 million men suffered from erectile dysfunction worldwide; this was expected to double by 2025. In the United States (US), the American Urological Association (AUA) estimates that there are 30 million men affected by erectile dysfunction. In Australia, the overall prevalence of erectile dysfunction was 61%; it is estimated that among those with normal erectile dysfunction, as much as 31.7% will develop erectile dysfunction at 5-year follow-up.

Throughout Asia, there exists a variation in the prevalence rate of erectile dysfunction, ranging from 2.0% to 81.8%. A study conducted in Malaysia showed a prevalence of 69.5% in males aged 40 to 79 years old. This prevalence was noted to increase each decade, from 49.7% of men in their 40s to 66.5%, 92.8%, and 93.9% in their 50s, 60s, and 70s, respectively, consistent other studies.

Erectile Dysfunction_Disease Background

Pathophysiology

The penis remains flaccid when the smooth muscle is contracted, in turn, smooth muscle contraction is regulated by a combination of adrenergic control, intrinsic myogenic control, and endothelium-derived contracting factors. With sexual stimulation, nitric oxide (NO) is released from non-adrenergic noncholinergic nerve fibers, while acetylcholine is released from parasympathetic cholinergic fibers. These results in an increase in cyclic guanosine monophosphate (cGMP), decreased intracellular calcium levels, and smooth muscle relaxation. Smooth muscle relaxation leads to blood flowing into the lacunar spaces of the corpora cavernosa, resulting in the compression of the subtunical venules, thus blocking venous outflow. Erectile dysfunction occurs when any of the above-mentioned processes are disrupted.

Risk Factors

Erectile dysfunction has common risk factors with cardiovascular diseases and may be the first presentation of an underlying medical condition (eg hypertension, diabetes mellitus [DM]). Studies have shown that erectile dysfunction has been associated with lower urinary tract symptoms, benign prostatic hyperplasia (BPH), sexual dysfunction regardless of age, pelvic trauma, surgery, radiation, other comorbidities, and various lifestyle factors.  

Comorbidities and Risk Factors Associated with Erectile Dysfunction

Vasculogenic

• DM
• Cardiovascular disease (hypertension, coronary artery disease [CAD], peripheral vascular disorders)
• Hyperlipidemia
• Recreational habits (eg drug and/or alcohol abuse, heavy smoking)
• Lack of regular physical exercise
• Obesity
• Major pelvic and prostate surgery (eg radical prostatectomy) or radiotherapy (pelvis or retroperitoneum)

Neurogenic

• Degenerative disorders (eg multiple sclerosis, Parkinson’s disease, multiple atrophy)
• Spinal cord trauma or diseases
• Stroke
• Central nervous system tumors
• Chronic renal failure, chronic liver failure
• Polyneuropathy
• Surgery of the urethra (eg urethral stricture, open urethroplasty)

Endocrine

• Hypogonadism/testosterone deficiency
• Hyperprolactinemia
• Hyper- and hypothyroidism

Psychiatric and Psychogenic

• Depression
• Anxiety disorders
• Relationship issues
• Stress
• Performance anxiety
• Loss of attraction

Drugs

• Antiandrogens (eg Finasteride)
• Antihypertensives (beta-blockers, Spironolactone, Methyldopa, thiazide diuretics)
• Narcotics
• Cimetidine
• Antidepressants
• Tranquilizers
• Others (eg Clonidine, Guanethidine, and Ketoconazole)

Penile Disorders

• Hypospadias, epispadias, micropenis
• Peyronie’s disease
• Severe phimosis

Others

• Obstructive sleep apnea (OSA)
• Sedentary lifestyle