Causes and Risk Factors of Erectile Dysfunction

When looking at the potential causes of erectile dysfunction, it's important to understand that more than one factor is often involved. As the American Urological Association puts it, "erectile function is the result of a complex interplay between vascular, neurologic, hormonal, and psychologic factors."

Keep this in mind as you read through the wide-ranging list of causes and risk factors for ED, which includes medications, health conditions, injury, smoking, and more.

Common Causes

Only a healthcare provider can confirm the cause of your erectile dysfunction. Often, an underlying disease or condition is to blame (see below). But one or more of the following issues may also be at play.

Age

Research shows that, in general, men experience more sexual problems as the years go by. The 1994 Massachusetts Male Aging Study, for example, found that rates of impotence increase as men age—moving from 5% at age 40 to 15% at 70.

In other words, it's entirely possible for a man to sidestep many of the potential causes of impotence by taking care of his physical health and his mental well-being as he gets older.

Medications and Treatments

Certain medications can interfere with nerve impulses or blood flow to the penis. According to a report from the Harvard Medical School, about 25% of men dealing with erectile dysfunction are having problems because of a medication they take. In fact, ED is one of the main reasons some men stop taking medication for conditions such as high blood pressure and depression.

Medications and other treatments that increase the risk of impotence include:

• Cancer chemotherapies, such as Myleran (busulfan) and Cytoxan (cyclophosphamide)
• Radiation to the pelvis during cancer treatment, which can cause injuries that lead to dysfunction
• High blood pressure medications, especially diuretics such as Microzide (hydrochlorothiazide) and beta-blockers such as Inderal XL (propranolol)
• Medications for psychiatric conditions, including anti-anxiety drugs, such as Paxil (paroxetine); antidepressants, such as Zoloft (sertraline); and anti-schizophrenia drugs, such as Seroquel (quetiapine)
• Tranquilizers such as Valium (diazepam)
• Hormonal medications for treating prostate cancer, such as flutamide and Lupron (leuprolide)
• Propecia (finasteride), which is used to treat an enlarged prostate as well as certain types of male hair loss
• High cholesterol and heart disease treatments, such as statins
• Ulcer treatments, including histamine H2-receptor antagonists such as Tagamet (cimetidine)
• Antihistamines that are used to treat allergies, such as Benadryl (diphenhydramine) and Vistaril (hydroxyzine)
• Antibiotics for treating fungal infections of the skin, such as Nizoral (ketoconazole)
• Nonsteroidal anti-inflammatory drugs (NSAIDs), such as Naprosyn (naproxen), when taken frequently

Stress and Anxiety

Sometimes a man will experience anxiety about sexual performance that inhibits his ability to get an erection, possibly because of a bad sexual experience or a previous occurrence of ED. Similarly, if a man and his partner are experiencing trouble in their relationship, the emotional and mental stress can take a toll on sexual function.

Surgery

Any surgery that involves structures in the pelvic area can damage penile nerves, blood vessels, or both, which in turn can affect a man's ability to get an erection or maintain one.

Another type of surgery that sometimes increases the risk of impotence is bowel resection for treating colorectal cancer, in which a portion of the large intestine (colon) is surgically removed along with the tumor. Certain variations of this procedure are most likely to cause ED:

• Left hemicolectomy (the removal of the left portion of the colon)
• Abdominoperineal resection (the removal of the rectum and anus)
• Proctectomy (the removal of the rectum)

In some cases of ED caused by bowel surgery, the problem results from loss of skin sensation. In others, the sacral reflex (the motor response that controls both the anal sphincter and muscles of the pelvic floor) are affected. What's more, the trauma of going through major surgery can cause stress that directly interferes with sexual function. 

Injury

An injury to the nerves, arteries, or veins of the pelvis has the potential to cause sexual problems. Men with spinal cord injuries have increased rates of erectile and ejaculatory problems, for example.

However, spinal cord injury does not necessarily prohibit sexual function. Some people with complete spinal cord injuries still experience arousal and orgasm from non-genital stimulation. While sexual desire can still be present, it can often be impacted by the trauma of the injury.

Diseases and Conditions

Erectile dysfunction rarely occurs in isolation. It is often a result of another health concern.

Diabetes and Heart Disease

ED is common among men with both type 1 diabetes and type 2 diabetes.

The longer a man has had diabetes, the more likely it is that he'll develop ED, especially if his blood glucose levels have not been well controlled. Complications of accompanying conditions such as high blood pressure and high cholesterol can also play a role in impotence. A man with diabetes who also smokes increases his risk of developing ED.

Heart disease and diabetes are often linked together, because coronary artery damage is a complication of diabetes as well. Coronary artery disease can also affect sexual function on its own, but erectile dysfunction is nine times as likely in men who suffer from both coronary artery disease and diabetes than in men who have diabetes alone.

Hypertension

Given that an erection depends on adequate blood flow to the penis, it's easy to see how any condition or medical problem affecting the heart and other structures in the cardiovascular system might have an impact on erectile function. This is particularly true for high blood pressure (hypertension).

Although scientists don't understand exactly how this condition can lead to ED, one theory is that high arterial pressure in the small vessels of the penis may cause microscopic tears to the vessel walls. In the process of repairing these tears, the arteries become thicker and less able to supply needed blood to the spongy erectile tissues of the penis.

Other potential factors in hypertension that may play a role in ED:

• Reduced hormone production. Elevated pressure in the circulatory system affects the production of certain hormones, including those that regulate sexual drive and erection response. There is also some evidence that men with high blood pressure have lower sperm counts and testosterone levels than men with normal blood pressure, which in turn may lower the hormonal response to sexual stimulation. 
• Low levels of nitric oxide. Some studies have shown that, over time, men with long-term hypertension may produce less nitric oxide, an agent that makes blood vessels relax, or dilate. Erectile dysfunction may result when there's not enough nitric oxide to sufficiently relax blood vessels and allow blood to fill the penis.
• Venous leaks. In order to maintain an erection, blood has to be supplied to and remain in the penis. Some research suggests that men with high blood pressure may have trouble maintaining an erection because the increased pressure forces blood out of the erectile tissues of the penis and into the veins. In this theory, the “push” on the small closing valves of the veins is stronger than the veins’ ability to resist, meaning the veins can't “close” tightly enough to stop blood from passing out of the penis.

​Psychological Conditions

A number of psychological concerns are associated with sexual function problems in men. Depression, anxiety, post-traumatic stress disorder, and even issues with anger have all been related to problems with desire, erectile function, and ejaculation. 

Other Concerns

There are a number of other conditions and diseases that can impact sexual function in men, leading to problems such as ED. Among these are: 

• Low testosterone. Testosterone declines by 1% per year in men after age 30. A normal testosterone level helps to support normal erectile function. Men with ED and low testosterone should be aware that ED medication (such as sildenafil or tadalafil) may be more effective if combined with testosterone therapy.
• Urinary and kidney problems. Men with urinary symptoms have been shown to have a higher rate of erectile problems as men without them. This includes problems such as overactive bladder as well as lower urinary tract symptoms.
• Chronic neurological diseases. Increased rates of ED and other types of sexual dysfunction have been seen in men with Parkinson's disease, epilepsy, stroke, and multiple sclerosis. These conditions may interfere with nerve signals between the brain and the penis.
• Obstructive sleep apnea (OSA). According to the National Sleep Foundation, a 2011 study by researchers at Mt. Sinai Medical Center in New York City found that men with erectile dysfunction were more than twice as likely to have OSA than men without ED.

Lifestyle Factors

Among the many potential causes of erectile dysfunction are quite a few that can be eliminated altogether.

Recreational Drugs

Over time, illegal and recreational drugs can cause serious damage to blood vessels, resulting in sometimes permanent erectile dysfunction. These include:

• Alcohol
• Nicotine from smoking and smokeless tobacco
• Amphetamines, such as Dexedrine (dextroamphetamine)
• Barbiturates, such as phenobarbital
• Cocaine
• Marijuana
• Methadone
• Opiates, such as heroin and OxyContin

Bicycle Riding

When biking, a significant amount of a man's weight rests on the perineum—the area of the body where the nerves and blood vessels of the penis pass—potentially causing injury to these structures. However, although riding has been associated with related erectile dysfunction, this form of exercise is more likely to be healthy than harmful for most men.

For one thing, most studies that have found a link between bicycle riding and ED have focused on men who spend long hours astride a bike, such as policemen who spend as many as 24 hours a week riding, and those who do long bike tours as amateurs or professionals.

It's worth noting that the MMSA also revealed that men who biked for three or fewer hours per week had a lower risk of developing ED, indicating bike riding as a form of moderate exercise might help prevent erectile dysfunction. 

Your bike seat may matter as well. There are saddles that have a hole or groove down the middle where the perineum would otherwise rest, but a significant part of this area still lies under the weight of the body when using them. Research has found that "no-nose" seats, which have a wider rear for the sitting bones to rest on, may help prevent damage, perineal numbness, and problems with erectile function.