Epidemiology of Inflammatory Bowel Disease

Something about our environment appears to confer a major risk of developing IBD. The prevalence of IBD varies with time, geography, socioeconomic condition, and occupation. The incidence of IBD in North America and Europe increased dramatically during the 20th century (Fig. 1). IBD is more common among people raised in the northern latitudes.[23-25] IBD is more common in urban than rural areas.[26] IBD is less common in persons who do manual labor and are exposed to dirt.[27] IBD is less common in military veterans if they were prisoners of war or served in combat in the tropics.[28] IBD is common in highly developed industrialized countries but is rare in less developed tropical countries. Studies of immigrants and their children show that this is not due to genetic differences between people living in developed versus less developed countries. The offspring of people who moved to developed countries have a much higher risk of IBD than their peers in their country of origin.[29-31] Furthermore, IBD emerges as countries develop.[32*]

This increase in IBD prevalence with economic development is unlikely to be due to better diagnostics or increased access to health care. Increases are seen in the same locale over time (Fig. 2) as lifestyles change.[33*] In addition, the emergence of IBD is not unique. Multiple sclerosis, insulin-dependent diabetes, allergic rhinitis, and asthma have a similar epidemiology.[34] It is becoming clear that changing our environment increases the risk of these immune-mediated diseases.

Incidence of Crohn Disease at Specific Locales Over Time