We read the interesting paper by Pardi et al on the epidemiology of microscopic colitis in Olmsted County, Minnesota, USA (Gut 2007; 56: 504–8). They concluded that the incidence of microscopic colitis increased significantly over time, and by the end of the study, the incidence and prevalence were significantly higher than reported previously. In fact, compared with other epidemiological studies, in the last years of the study period they describe the highest incidence figures of microscopic colitis ever reported.

However, is difficult to compare the crude incidence rates of several studies if we do not know the age structure of the population pyramid of each geographical area. As microscopic colitis is associated with older age, a higher incidence will be expected …