Most men experience occasional difficulty with erections, often due to stressful situations. In contrast, erectile dysfunction (ED) is a persistent problem of not being able to get or maintain an erection.

Although it is not a natural or inevitable part of aging, the incidence of ED increases as men get older. It’s estimated that between 15 million and 30 million American men suffer from the condition.

Diseases that damage blood vessels restrict blood flow to the penis. Over time, this damages the mechanism that facilitates erections.

One major cause of ED is atherosclerosis, which is more likely to occur with diabetes, which can also damage the nerves that enable the penis to function in a normal way. Studies have shown that 75 percent of men with coronary artery disease, in which plaque blocks blood flow, also have ED.

A link between these two conditions may be a deficiency of nitric oxide in the walls of blood vessels. Nitric oxide enables blood vessels to relax, allowing adequate blood flow.

ED is also associated with hypertension, elevated blood fats, obesity, and smoking. In addition, prostate surgery or cancer treatment can damage the nerves in the penis. ED can also be a side effect of blood pressure-lowering drugs, pain medications, antidepressants, or antihistamines.