Similar Geographic Variations of Mortality and Hospitalization Associated with IBD and Clostridium difficile Colitis

Background: Superinfection with Clostridium difficile can aggravate the symptoms of preexisting inflammatory bowel disease (IBD). The study served to assess whether the geographic variation of IBD within the United States might be influenced by C. difficile infection. Methods: Hospitalization data of the Healthcare Cost and Utilization Project (HCUP) from 2001-2006 and mortality data from 1979-2005 of the US were analyzed by individual states. Hospitalization and mortality associated with Crohn's disease (CD), ulcerative colitis (UC), and C. difficile colitis were correlated with each other, using weighted least square linear regression with the population size of individual states as weight. Results: Among the hospitalization rates, there were strong correlations between both types of IBD, as well as each type of IBD with C. difficile colitis. Similarly, among the mortality rates there were strong correlations between both types of IBD, as well as each type of IBD with C. difficile colitis. Lastly, each type of hospitalization rate was also strongly correlated with each type of mortality rate. In general, hospitalization and mortality associated with IBD tended to be frequent in many of the northern states and infrequent in the Southwest and several southern states. Conclusions: The similarity in the geographic distribution of the 3 diseases could indicate the influence of C. difficile colitis in shaping the geographic patterns of IBD. It could also indicate that shared environmental risk factors influence the occurrence of IBD, as well as C. difficile colitis.