The Inflammatory Bowel Disease in South-Eastern Norway (IBSEN) study group was initially established to ascertain the precise incidence of inflammatory bowel disease (IBD) within a specific region of Norway, thereby contributing to a global initiative aimed at elucidating the increasing prevalence of these conditions. The study was designed to foster close collaboration among national and international experts, including gastroenterologists, specialists, and private practitioners within the study area. Patients were enrolled prospectively over a 4-year period, from January 1, 1990, to December 31, 1993, based on established international diagnostic criteria and a follow-up protocol encompassing 1, 5, 10, 20, and 30-year intervals. The consortium operated through a bidirectional communication network connecting primary and secondary specialized hospitals, encompassing general hospitals and research laboratories. In 2017, the IBSEN III study was launched to facilitate a comparison of clinical and epidemiological outcomes with those of the original IBSEN study, involving an expanded catchment area and more extensive clinical and molecular assessments of the cohort. This narrative review reflects the consortium's activities through 2024 and provides comprehensive details regarding the research areas and outcomes of national and international collaborations for both IBSEN study.
Keywords: Crohns disease; IBD; clinical; epidemiology; ulcerative colitis.
The IBSEN study in South-Eastern Norway: thirty years of progress in how we understand and treat inflammatory bowel disease, thanks to clinical research and scientific collaboration The Inflammatory Bowel Disease in South-Eastern Norway (IBSEN) study group was formed to determine the exact number of new cases of IBD in a specific area of Norway. This was part of a larger global effort to understand why these diseases are becoming more common. The study was created to encourage collaboration between Norwegian and international experts, including gastroenterologists, other specialists, and local doctors. Patients were enrolled in the study over four years, from January 1, 1990, to December 31, 1993. Their enrollment was based on standard international diagnostic criteria, and they were followed up at 1, 5, 10, 20, and 30-year intervals. The study group used a communication network linking local and specialized hospitals, including general hospitals and research labs. In 2017, the IBSEN III study began to compare clinical and epidemiological results with the original IBSEN study. This involved a larger geographic area and more detailed clinical and molecular evaluations of the participants. This report offers complete details about the research areas and the results of national and international collaborations for both IBSEN studies.
© The Author(s), 2026.