Epidemiologic clues to inflammatory bowel disease.

In this article, the recent literature exploring the epidemiology of inflammatory bowel disease (IBD) is reviewed. Epidemiologic studies present data on disease burden, but may also provide clues to disease etiology. The emergence of IBD in developing nations warrants a systematic search for environmental changes in those countries to explain the evolution of IBD. The hygiene hypothesis suggests that an alteration in the microbial environment experienced by the host facilitates the evolution of chronic immune-mediated diseases. One complex database study suggested that areas with high species richness of human intestinal helminthes are areas with genetic changes in interleukin gene loci. In other words, over the years, the microbial ecology has affected human genetics, which in turn would have an impact on immune responses. Other factors affect the gut microbiome, and several studies have explored the increase in incidence of IBD in relation to such factors as exogenous infections, use of antibiotics, and diet.