About half a million Americans, or 7 people out of every 100,000 have Crohn’s disease. Of these, about 4% are children under age 5, and 10% are under age 18. Most people are diagnosed with the disease between ages 15 and 35, although they may have had the disease before that. In the United States the rate of Crohn’s disease has been increasing since the 1950s.
Although most common among non-Hispanic whites, the rate of Crohn’s disease among American blacks, especially urban blacks, has been steadily increasing. Jews who trace their ancestry middle Europe are 2-4 times more likely to develop the disease than the general white population or Jews who trace their origins to other regions. Internationally, Crohn’s disease is rare in Africa, Asia, and South America. It is more common in urban areas than in rural areas, suggesting that environment plays a role in the disease.