Increased Incidence of Inflammatory Bowel Disease: The Price of the Decline of Infectious Burden?

Hélène Feillet; Jean-François Bach

Disclosures

Curr Opin Gastroenterol. 2004;20(6) 

In This Article

Suggestive Epidemiological Data

Inflammatory bowel disease is not evenly distributed worldwide. There is a clear tendency to a higher incidence in developed countries compared with less-developed countries.[1*] The argument of possible underdiagnosis in the latter countries is valid but probably only partially explains the difference. The uneven distribution of IBD in the different American states and European countries is important in this regard since one may reasonably assume that the knowledge and awareness of the disease are similar in all these regions. Efforts have been developed to determine which factors might explain these geographical differences. Genetic factors should be discussed first. They may play a role, although this role is not well documented. In any event, their role is modest if one considers migrants from low-incidence to high-incidence countries who develop the disease with the incidence of the country where they immigrated to, as observed with migrant South Asians to Europe.[4] In fact, the most obvious factor explaining the uneven IBD geographical distribution is the socioeconomic level. This is true when considering different countries, but also different regions in a given country as was demonstrated in Canada.[5] Other factors may intervene, notably climate (temperature) and diet but they have not been fully documented. The next question is to determine how socioeconomic levels can affect disease incidence. Cohort studies have indicated that sanitary conditions probably play a major role, at least for Crohn disease, suggesting the responsibility of a declined rate of infections for increased disease incidence.[6,7] In the same vein, it is interesting to note that in families with several children, IBD is more common in the firstborn child who is not exposed to infections transmitted by siblings.[8*] If indeed the infectious environment matters, one may assume that high socioeconomic level operates through its association with high-quality water and food (cold chain) as well as with high medical standards, leading to increased (even if not always justified) usage of antibiotics.

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