Erectile dysfunction, sometimes called “impotence,” is the repeated inability
to get or keep an erection firm enough for sexual intercourse. The word
“impotence” may also be used to describe other problems that interfere with
sexual intercourse and reproduction, such as lack of sexual desire and problems
with ejaculation or orgasm. Using the term erectile dysfunction makes it clear
that those other problems are not involved.
Erectile dysfunction, or ED, 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 ED and estimating its incidence difficult.
Estimates range from 15 million to 30 million, depending on the definition used.
According to the National Ambulatory Medical Care Survey (NAMCS), for every
1,000 men in the United States, 7.7 physician office visits were made for ED in
1985. By 1999, that rate had nearly tripled to 22.3. The increase happened
gradually, presumably as treatments such as vacuum devices and injectable drugs
became more widely available and discussing erectile function became accepted.
Perhaps the most publicized advance was the introduction of the oral drug
sildenafil citrate (Viagra) in March 1998. NAMCS data on new drugs show an
estimated 2.6 million mentions of Viagra at physician office visits in 1999, and
one-third of those mentions occurred during visits for a diagnosis other than
In older men, ED 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 ED. Incidence increases with
age: About 5 percent of 40-year-old men and between 15 and 25 percent of
65-year-old men experience ED. But it is not an inevitable part of aging.
ED is treatable at any age, and awareness of this fact has been growing. More
men have been seeking help and returning to normal sexual activity because of
improved, successful treatments for ED. Urologists, who specialize in problems
of the urinary tract, have traditionally treated ED; however, urologists
accounted for only 25 percent of Viagra mentions in 1999.
How does an erection occur?
The penis contains two chambers called the corpora cavernosa, which run the
length of the organ (see figure 1). A spongy tissue fills the chambers. The
corpora cavernosa are surrounded by a membrane, called the tunica albuginea. The
spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and
arteries. The urethra, which is the channel for urine and ejaculate, runs along
the underside of the corpora cavernosa and is surrounded by the corpus