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Inflammatory bowel disease (IBD) is a chronic idiopathic inflammatory disease of the gastrointestinal tract. Ulcerative colitis (UC) and Crohn’s disease (CD) are the two major types of IBD.
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GLOBAL CONSIDERATIONS: EPIDEMIOLOGY
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UC and CD have emerged as global diseases in the twenty-first century. They affect >2 million individuals in North America, 3.2 million in Europe, and millions more worldwide. Since the late 1990s, the majority of studies on CD and UC show stable or falling incidence in the Western world. The disease burden remains high, with a prevalence of >0.3% in North America, Oceania, and most countries in Europe. In newly industrialized countries in Africa, Asia, and South America where there is increased urbanization and Westernization, the incidence of IBD has been rising and mirrors the prior increase of IBD in the Western world in the twentieth century. For example, in Brazil, the annual percent change is +11.1% (95% confidence interval [CI], 4.8–17.8%) for CD and +14.9% (95% CI, 10.4–19.6%) for UC, whereas in Taiwan, the annual percent change is +4.0% (95% CI, 1.0–7.1%) for CD and +4.8% (95% CI, 1.8–8.0%) for UC. In a study of newly diagnosed IBD cases between 2011 and 2013 from 13 countries or regions in the Asia Pacific, the mean annual IBD incidence per 100,000 was 1.50 (95% CI, 1.43–1.57). India (9.31; 95% CI, 8.38–10.31) and China (3.64; 95% CI, 2.97–4.42) had the highest IBD incidences in Asia. The highest reported prevalence values were in Europe (UC, 505 per 100,000 in Norway; CD, 322 per 100,000 in Germany) and North America (UC, 286 per 100,000 in the United States; CD, 319 per 100,000 in Canada). The most likely factors that explain the geographic variability of IBD rates, especially the rising incidence in developing countries and urban areas, are environmental variables including changes in diet (with downstream effects on the intestinal microbiota), exposure to sunlight or temperature differences, and socioeconomic status and hygiene (Table 326-1).
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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 higher in ...