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Inflammatory bowel disease (IBD) is an immune-mediated chronic intestinal condition. Ulcerative colitis (UC) and Crohn's disease (CD) are the two major types of IBD.

The incidence of IBD varies within different geographic areas. CD and UC both occur at the highest incidence in Europe, the United Kingdom, and North America. In North America, incidence rates range from 2.2–14.3 cases per 100,000 person-years for UC and from 3.1–14.6 cases per 100,000 person-years for CD (Table 295-1). Prevalence ranges from 37–246 cases per 100,000 person-years for UC and from 26−199 cases per 100,000 person-years for CD. In Europe, incidence ranges from 1.5–20.3 cases per 100,000 person-years for UC and from 0.7–9.8 cases for CD; prevalence ranges from 21.4–243 cases for UC and from 8.3–214 cases per 100,000 person-years for CD. IBD has been rare in other areas except Israel, Australia, and South Africa. The incidence of IBD, especially UC, is rising in Japan, South Korea, Singapore, northern India, and Latin America, areas previously thought to have low incidence. The incidence of UC has increased sixfold in the past two decades in Hong Kong. Reports from the United States, Poland, Denmark, and South Korea indicate that the incidence of pediatric IBD is increasing rapidly as well. The highest mortality is during the first years of disease and in long-duration disease due to the risk of colon cancer. In a Danish population study, the standardized mortality ratios for CD and UC were 1.31 and 1.1, respectively.

Table 295-1 Epidemiology of IBD

The peak age of onset of UC and CD is between 15 and 30 years. A second peak occurs between the ages of 60 and 80. The male to female ratio for UC is 1:1 and for CD is 1.1–1.8:1. UC and CD have two- to fourfold increased frequency in Jewish populations in the United States, Europe, and South Africa. Furthermore, disease frequency differs within the Jewish populations. The prevalence of IBD in Ashkenazi Jews is about twice that of Israeli-born, Sephardic, or Asian Jews. The prevalence decreases progressively in non-Jewish white, African-American, Hispanic, and Asian populations. Urban areas have a higher prevalence of IBD than rural areas, and high socioeconomic classes have a higher prevalence than lower socioeconomic classes.

The effects of cigarette smoking are different in UC and CD. The risk of UC in smokers is 40% that of nonsmokers. Additionally, former smokers have a 1.7-fold increased risk for UC than people who have ...

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