Impotence can be a total inability to achieve
erection, an inconsistent ability to do so, or a tendency to sustain
only brief erections. These variations make defining impotence
and estimating its incidence difficult.
Incidence increases with age: About 5 percent of 40-year-old men
and between 15 and 25 percent of 65-year-old men experience impotence.
But it is not an inevitable part of aging. In older men, impotence
usually has a physical cause, such as disease, injury, or side
effects of drugs. Any disorder that causes injury to the nerves
or impairs blood flow in the penis has the potential to cause