May 16, 2012

Erectile Dysfunction (ED) in the Elderly

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Erectile Dysfunction (ED) in the Elderly

Devraj Munikrishnappa, M.D.

Dr. Munikrishnappa is Adjunct Clinical Instructor, Department of Geriatrics, Saint Louis University School of Medicine, St. Louis, Missouri.

There may be hundreds of things that can go wrong with sex from the male point of view, but scientists divide male sexual dysfunction into three categories. They are: erectile dysfunction (problems with erection), ejaculatory dysfunction (problems with ejaculation) and decrease in libido (loss of interest in sex).

The most familiar to anyone who watches sports on TV is erectile dysfunction, called "ED" for short. The technical definition of ED is the inability to achieve or maintain enough of an erection for satisfactory sexual performance.(1) Most men have the problem at one time ot another — 52% of American men aged 40 to 70 years according to a large study called the Massachusetts Male Aging Study (MMAS).(2) More recent studies have confirmed the common perception that erection problems become more frequent with age.(3)(4)

One reason for this is simply the normal effects of aging on the body. With age, structural changes occur in the penis that make it, like any aging muscle, work less well. Age brings a decreased concentration of elastic fibers and smooth muscle fibers, both of which play an important part in erection.(5) Another factor is age-related disease. ED is frequently associated with atherosclerosis, diabetes and other diseases that also become more common as we age.(6)(7)

An erection is not a simple thing. It requires a complex interaction involving the nervous system, blood flow, hormones and the individual's psychological make-up. It generally occurs in one of three different ways — at night during the REM (rapid eye movement) phase of sleep, from physical touching of the genitals and from psychological stimuli such as a reaction to smell, sight or memory.(8)

An erection is not a simple thing. It requires a complex interaction involving the nervous system, blood flow, hormones and the individual's psychological make-up.

The muscles within the penis play a vital role in erection. When these muscles are contracted, only the small amount of blood needed to keep the tissues alive is allowed; this results in a flaccid, or un-erect, penis.(9)

With sexual stimulation, these muscles relax, allow more blood to flow into the penis and cause erection. This happens according to the following complex series of stages. While this may be too technical to be of much use to the average non-medical person, it serves to illustrate the amazing complexity of what may seem a simple bodily function.(10)(11)

Sexual stimulus
↓
Neurotransmitters including nitric oxide (NO) released from nonadrenergic and noncholinergic cavernous nerve terminals and endothelial cells
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Interacts with enzyme guanylyl cyclase to increase cyclic guanosine monophosphate (cGMP) within the smooth muscle cell*
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Decreased intra-cellular calcium
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Smooth muscle relaxation
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Blood vessel dilatation
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Increased blood flow into the penis
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Sinusoidal relaxation with trapping of blood
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Compression of subtunical venular plexus between tunica albuginea and peripheral sinusoids causing decreased venous outflow Compression of emissary veins between the inner circular and the outer longitudinal layers by further stretching of tunica causing further decrease in venous outflow to a minimum
↓
PO2 increases to about 90 mm Hg and intracavernous pressure to around 100 mm Hg, causing the penis to rise from the dependent position to the erect state (the full-erection phase)
↓
With contraction of the ischiocavernous muscles, a further pressure increase to several hundred millimeters of mercury occurs causing rigid-erection phase.

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