health

It is estimated that there are about 500,000 persons with Crohn disease
in the United States, with another 500,000 suffering from ulcerative
colitis. Another statistic given by some doctors is seven cases per
100,000 in the general population in Canada and the United States.
Crohn is primarily a disorder of adults, most often beginning in late adolescence
or the early adult years. The most common age at onset is between
fifteen and thirty years, although the disorder may begin at any age.
The rate of Crohn disease in North America has been increasing
since the 1960s, although the reasons for the increase are unknown.
Southern Europe, South America, Africa, and Asia have considerably
lower rates of the disease—as low as 0.5–0.08 cases per 100,000 people.
Around the world, however, the rates of Crohn disease are higher in cities
than in rural areas and higher among people with higher incomes than
among lower-income groups.
One argument for suspecting a genetic factor in Crohn disease is that
it runs in some families; people with siblings who have the disease are
thirty times more likely to develop it than the normal population. It is also
relatively common among certain ethnic groups, particularly Jews of
Eastern European origin. A two- to four-fold increase in the frequency of
Crohn disease has been found among the Jewish population in the United
States, Europe, and South Africa compared to other ethnic groups.
In terms of other ethnic groups in the United States, Crohn disease
appears to be slightly more common in non-Jewish Caucasians than in
African or Asian Americans. The disease is almost twice as likely to occur
in men than in women.