Risk Factors
An estimated 1 - 2 million Americans suffer from inflammatory bowel disease (IBD) and about 400,000 of these patients have Crohn's disease. (This wide statistical variation is due to the difficulty in diagnosing these disorders and because people in remission may not be identified.) The number of people with Crohn's disease may be increasing, and Crohn's disease is now considered to be the second most common chronic inflammatory disorder (after rheumatoid arthritis).
IBD often runs in families. The incidence may vary depending on gender, age, and geography:
- Women may be slightly more at risk for Crohn's disease than men. Both genders are equally at risk for ulcerative colitis.
- IBDs in general are diagnosed most often in young people between the ages of 10 and 19, but they can occur at any age. Another lesser peak onset occurs between ages 50 and 80. About 2% of IBD cases appear in children below age 10. Between 10 - 15% of patients with Crohn's are children, and the childhood prevalence appears to be increasing.
- IBD occurs four times more often in Americans of Northern European descent than in African Americans. Scandinavia has the highest rate of Crohn's disease in the world. Studies in Britain suggest, however, that Asians may have a higher rate of IBD than people of European descent. Jewish people of European descent have an even higher risk: Five times that of the general population.
- IBD seems to be more common among city than country dwellers and occurs more frequently in developed than in less developed nations, indicating that both genetic factors and environmental conditions, such as diet, may be involved in its development.
- People who are left-handed have a significantly higher risk for both IBDs as well as certain other diseases associated with problems in the immune system.
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