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.
GLOBAL CONSIDERATIONS: EPIDEMIOLOGY
The highest incidence rates of CD and UC have been reported in northern Europe, the United Kingdom, and North America. Countries in the Pacific, including New Zealand and Australia, which share many possible environmental risk factors and similar genetic background as northwest Europe and North America, have high incidence rates of IBD.
The highest reported incidence rates are in Canada (19.2 per 100,000 for UC and 20.2 for CD), Northern Europe (24.3 per 100,000 for UC in Iceland and 10.6 per 100,000 for CD in the United Kingdom), and Australia (17.4 per 100,000 for UC and 29.3 per 100,000 for CD). Prevalence is highest in Europe (505 per 100,000 for UC in Norway and 322 per 100,000 for CD in Italy) and Canada (248 per 100,000 for UC and 319 per 100,000 for CD) (Table 319-1). Based on these estimates ~0.6% of the Canadian population has IBD.
TABLE 319-1Epidemiology of IBD ||Download (.pdf) TABLE 319-1 Epidemiology of IBD
| ||Ulcerative Colitis ||Crohn's Disease |
|Incidence (North America) per person-years ||0–19.2 per 100,000 ||0–20.2 per 100,000 |
|Age of onset ||Second to fourth decades and seventh to ninth decades ||Second to fourth decades and seventh to ninth decades |
|Ethnicity ||Jewish > non-Jewish white > African American > Hispanic > Asian |
|Female/male ratio ||0.51–1.58 ||0.34–1.65 |
|Smoking ||May prevent disease (odds ratio 0.58) ||May cause disease (odds ratio 1.76) |
|Oral contraceptives ||No increased risk ||Hazard ratio 2.82 |
|Appendectomy ||Protective (risk reduction 13–26%) ||Not protective |
|Monozygotic twins ||6–18% concordance ||38–58% concordance |
|Dizygotic twins ||0–2% concordance ||4% concordance |
|Antibiotic use in the first year of life ||2.9× the risk of developing childhood IBD
In countries that are becoming more Westernized, including China, South Korea, India, Lebanon, Iran, Thailand, and countries in the French West Indies and North Africa, IBD appears to be emerging, emphasizing the importance of environmental factors in disease pathogenesis. In Japan, the prevalence of CD has risen rapidly from 2.9 cases per 100,000 in 1986 to 13.5 per 100,000 in 1998, whereas in South Korea, the prevalence of UC has quadrupled from 7.6 per 100,000 in 1997 to 30.9 per 100,000 in 2005. In Hong Kong, the prevalence of UC almost tripled from 2.3 in 1997 to 6.3 per 100,000 over a 9-year period. In Singapore, the prevalence of CD increased from 1.3 in 1990 to 7.2 per 100,000 in 2004. In China the number of cases of UC has increased by fourfold between 1981–1990 and 1991–2000.
Increasing immigration to Western societies also has an impact on the incidence and prevalence of IBD. The prevalence of UC among southern Asians who immigrated to the United Kingdom (UK) was ...