The incidence of ulcerative colitis has increased in many parts of the world during the second part of the twentieth century. In the county of Uppsala in the middle part of Sweden, the epidemiology of ulcerative colitis has been studied during two different time periods, 1945-1964 and 1965-1983. These figures have now been compared to the present day situation, 2005-2007.
The incidence figures in the two first studies were the results of retrospective studies but the figures from 2005 to 2007 were generated prospectively. The clinical characteristics during 1945-1964 were described according to the Montreal classification and a comparison between the first and third study periods could therefore be done.
During the study period, the population of the county increased from 146000 to 323270 inhabitants. The crude incidence of ulcerative colitis increased from 2 to 19.2 new cases per 100000 inhabitants/year. The age distribution was remarkably stable when the first 20 years was compared with the last 3 years (mean age 36 vs. 38.1 and range 2-84 vs. 3-84) except for those below 11 years of age.
Between 1945 and 2007 the incidence of UC in the County of Uppsala increased from 2 to 19.2 new cases/100000. The increase affected all age groups except those below 11 years of age.