Erectile dysfunction and vascular disease as a cause of erectile dysfunction
After Luciano Kolodny, MD, Postgraduate Medicine, Vo; 114 Number 4 October 2003
Many men are reluctant to talk about sexual problems. But doctors are recommended to ask about erectile dysfunction in patients as young as forty years of age, because ED may be a sign of undetected vascular disease.
We look here at the connection with vascular disease and suggest how doctors can help patients reduce the chance of succumbing to either erectile dysfunction or any underlying disorders.
Erectile dysfunction is a problem that can be distressing for men and their partners; it may also be the first sign of underlying vascular disease.
One of the most respected and cited studies on the epidemiology of erectile dysfunction is the Massachusetts Male Aging Study, which showed that over half of 1,290 men aged between 40 and 70 years of age had some degree of erectile dysfunction. About 10% had total erectile dysfunction. The MMAS also showed the extremely clear epidemiologic link between coronary artery disease, diabetes, and erectile dysfunction.
In a follow-up study nearly nine years later, the overall incidence rate of ED was 26 cases in 1,000 men over one year; not surprisingly, the rate increased with age and the presence of diabetes, heart disease, and hypertension (high blood pressure).
Other pages on this website about the causes of erectile dysfunction and impotence
Other sections on erectile dysfunction
Classification of erectile dysfunction
Erectile dysfunction can be classified as psychogenic, organic or of mixed origins. The organic classification further breaks down into neurogenic, hormonal, vascular and cavernosa. Among these, vascular disease is thought to be the most common cause.
Vascular risk factors
Atherosclerosis is the predominant cause of vasculogenic erectile dysfunction. The changes associated with atherosclerosis include but are not limited to endothelial injury, cellular migration, and smooth-muscle proliferation.
A wide variety of factors influence these changes, for example, cytokines, antioxidants, thrombosis, growth factors and metabolic alterations, for example those which are associated with diabetes.
One hypothesis is that ageing of the endothelium alters nitric oxide levels. Some evidence to support this exists: for example, up-regulation of endothelial nitric oxide synthase has been found in corporal smooth-muscle cells and endothelium of aging rabbits, rabbits which had impaired endothelium-mediated cavernosal relaxation.
It's possible that this up-regulation is some kind of compensatory mechanism associated with endothelial dysfunction linked to ageing.
This is mediated through (a) the toxic effects on the vascular endothelium, (b) nicotine-induced smooth-muscle contraction inside the cavernosal body, (c) decreases in nitric oxide synthase activity inside the penis, and (d) decreases in neuronal nitric oxide synthase levels.
Diabetes is a major risk factor associated with the cause of erectile dysfunction. In the MMAS, men with diabetes showed levels of ED three times greater than men without diabetes: 28% versus 9.6%. The origin of erectile dysfunction in diabetic men may be linked to increased atherosclerosis, changes in the corporal erectile tissue, and nerve cell damage.
Such changes may include the degeneration of smooth-muscle, endothelial cell dysfunction, and unusual patterns of collagen deposition.
Furthermore, advanced glycosylated end-products are found at elevated levels in tissues of the penis of diabetic men with reduced nitric oxide.
Research on corpus cavernosum tissue obtained from diabetic men has demonstrated impairment in neurogenic function and endothelium dependent relaxation of smooth muscle of the corpus cavernosum.
Correlation between high blood pressure and erectile dysfunction was noted in the Massachusetts Male Aging Study.
In another study, the incidence and degree of severity of erectile dysfunction were not significantly different between different types of antihypertensive medications nor were they related to the number of drugs in use: which suggests that both hypertension and the medications prescribed for it can contribute to the cause of erectile dysfunction.
Hyperlipidemia is another important factor in the origin of erectile dysfunction. Endothelium-dependent relaxation in the vascular beds of men with hypercholesterolemia is impaired a finding described in many studies. Fortunately, this impairment is reversible with the assistance of certain of the lipid-lowering agents.
Erectile dysfunction can be a useful marker for cardiovascular disease
Erectile dysfunction is often a sign of vascular disorder. In a study of almost one thousand patients who sought advice for erectile dysfunction, 18% had undiagnosed (and untreated) high blood pressure, 15% were found to have benign prostatic hyperplasia, 16% were found to have diabetes, 5% were found to have ischemic heart disease, and 4% were found to have prostate cancer. A much smaller figure, 1%, were found to be depressed.
The chief link between cardiovascular disease and erectile dysfunction is the role of the vascular endothelium, which regulates circulation. Nitric oxide formation in the endothelium is a crucial part of erectile function; if generation of nitric oxide is impaired or compromised, erectile dysfunction may follow. And endothelial cell dysfunction may well precede the formation of arterial plaques - this is quite common in men with diabetes or cardiovascular disease.
Because of these close associations, erectile dysfunction and vascular disease share several risk factors: cigarette smoking, hyperlipidemia, and hypertension, to name but three.
The link between vascular disease and erectile dysfunction indicates these risk factors may be targets for prevention of disease. Indeed, erectile dysfunction may be an independent indicator of coronary artery disease, while the progression of coronary artery disease may correlate with the level of erectile dysfunction.
Cardiovascular risk factors act together to exert an adverse effect on the functioning of the endothelium.
A summary of all these findings can be represented thus:
Because erectile dysfunction is often the first sign of cardiovascular disease or diabetes, doctors should make an effort to discuss erectile dysfunction with their male patients. And since erectile dysfunction usually has a significant effect on a man's relationship with his partner, identifying it can produce benefits for the couple as well as the man himself.
Currently, there is a choice of drugs to treat erectile dysfunction, and the outcomes tend to be good. Medications such as antihypertensive and lipid-lowering agents can be administered at the same time, and management of ED may encourage a man to stop smoking or lose weight. Cardiac risk assessment and management is needed in all men with erectile dysfunction.