The Inflammatory Bowel Disease in South-Eastern Norway study: three decades of advancements in clinical understanding and scientific partnerships

Abstract

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.

Plain language summary

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.

Keywords

Crohns disease ulcerative colitis clinical epidemiology IBD

Background

After World War II, reports showed an increasing prevalence of inflammatory bowel disease (IBD) in the Western world.¹ Studies from major clinical centers between the 1960s and the 1980s reported a rise in the prevalence of IBD, likely to be caused by improved diagnostics and early disease recognition. Fiberoptic endoscopy played a crucial role in gastroenterological diagnostics including the diagnosis of IBD during these years.² In Norway, mandatory endoscopic training programs for gastroenterologists and gastroenterological surgeons were introduced in the early 1970s. Ileocolonoscopy with biopsies became the gold standard for the diagnosis of IBD and differentiation between ulcerative colitis (UC) and Crohn’s disease (CD).³

The awareness of increased frequency of IBD, based on national and international observations,^4–6 gave rise to epidemiological studies in Norway. Early Norwegian data from 1963 to 1969 indicated low incidence rates of UC (3.3) and CD (1.0) in southeastern Norway,⁷ while higher rates were reported from western Norway in 1976–1980: 10.2 for UC and 3.7 for CD,⁸ and in 1984–1985: 14.8 for UC and 5.3 for CD.^9,10 In northern Norway, data from 1983 to 1986 revealed incidence rates for UC and CD of 12.3 and 5.3, respectively.^11,12

Initiative behind and start of the Inflammatory Bowel Disease in South-Eastern Norway study

In September 1988, a European prospective, population-based incidence study of IBD was presented in Rotterdam, hypothesizing similar incidence rates across Europe. The proposal intended to include all Western European nations (EC-IBD). In the spring of 1989, representatives of the project were invited to the European Parliament in Brussels to discuss the protocol, as a population-based study of this scale was new to the European Parliament. EU funding was secured for the following years.

In 1989, preparatory documentation was developed for a prospective study involving 1236 general practitioners, who were tasked with registering all patients, including those exhibiting subtle or atypical symptoms. Collaboration with 15 local hospitals was also established. The study commenced in January 1990, with a 4-year enrollment period designed to mitigate annual fluctuations. In its initial year, the Norwegian study, “Inflammatory Bowel South-Eastern Norway” was renamed “The Inflammatory Bowel Disease in South-Eastern Norway (IBSEN) Study Group.” The IBSEN study then encompasses the organization, all involved personnel, and the study methodologies, including methods, resources, and organizational structure.

This narrative review reflects the IBSEN group (healthcare and non-healthcare participants) activities from the beginning through 2024. A professional organization assisted for the application to another EU-grant and for EU-communication. For this application, a major contribution was attributed by the IBSEN study group and 12 other centers, with a decentralized structure, and with the planning of fellowships in different countries.

The John Lennard-Jones diagnostic criteria, combined with ileocolonoscopy, were considered the new gold standard for diagnosis.³ Initial results from centers across Northern and Southern Europe indicated that most achieved at least 90% complete ileocolonoscopy rates at diagnosis.

The IBSEN study began in January 1990, followed by the EC-IBD study in autumn 1991. Consequently, 2 years of the IBSEN inclusion period overlapped with the EC-IBD study, matching the 2-year inclusion period of the other 18 EC-IBD centers. Within the EC-IBD study, the IBSEN cohort represented the most substantial group included accounting for 25% of the 1505 European patients. The 1-year follow-up, reported in 1992, was a significant milestone in the EC-IBD study. The IBSEN study achieved a near 100% endoscopy re-examination rate at the 1-year follow-up, a scientific strength that enabled the later study on mucosal healing (Figure 1), which relied on these complete endoscopic data.¹³

Figure 1.

Kaplan–Meier curves show colectomy rates in (a) UC and resection in CD patients >1-year post-diagnosis with or without mucosal healing at 1 year. Kaplan–Meier curves illustrate the time to colectomy in patients with UC) (a) and CD (b), measured from 1-year post-diagnosis. The upper line represents the proportion of patients with established mucosal healing at the 1-year visit who did not require subsequent colectomy in UC or resection in CD. Conversely, the lower line represents the proportion of patients without mucosal healing at the 1-year visit who did not require subsequent colectomy (UC) or resection (CD).

The progress of the IBSEN study group within and outside the EC-IBD

The study’s epidemiologic design necessitated international expertise, leading to the invitation of the late Professor Anders Ekbom from Uppsala University. He was already serving as an epidemiologic and statistical advisor for EC-IBD. This project successfully integrated clinical knowledge into an epidemiologic framework, highlighting the value of clinical epidemiology.

Patients underwent comprehensive clinical characterization, with specialists at each participating center in Southeast Norway reviewing all clinical information, laboratory results, and histological findings. The study management at the university hospital implemented quality control measures for all incoming data, ensuring accurate and consistent identification of UC and CD subgroups.

The first thesis represented the mainstay of clinical epidemiology in IBD at that time.^14–17 The baseline, and early follow-up data from the IBSEN study, represented important contributions to the establishment of the Vienna Classification,¹³ whereby the validation of disease characteristics could clearly be demonstrated for diagnostic subgroups, showing different patterns between population-based (Copenhagen, Olmsted County, and Oslo) and hospital registrations (New York and Toronto; Figure 2).¹⁸

Figure 2.

Appropriate assignment to age at diagnosis of Crohn’s populations from Europe (Copenhagen, Oslo) and North America (Olmsted) in 791 individuals. Allocation of patients to the variable Age at Diagnosis. Crohn’s populations from Europe (Copenhagen, Oslo) and North America (Olmsted). Al: below 40 years; A2: equal to or above 40 years. When compared with Crohn’s patients from referral centers (medical: New York, USA; surgical: Toronto, Canada), the allotment was highly different.

Initially, the IBSEN study did not plan to include basic research and biology as a research area, and blood specimens were collected solely for diagnostic purposes. In 1999, a collaboration with University Hospital in Kiel was initiated for combined genetic and clinical analysis of NOD2-susceptibility in CD.¹⁹ This collaboration led to an early publication showcasing the novel discovery and earned the group a finalist nomination for the 2002 European Descartes Prize, awarded by the European Commission in Munich. A subsequent collaboration with the Norwegian PSC center at Rikshospitalet, which houses the database and biological material, has been ongoing for two decades.

Upon an invitation by Centocor to study mucosal healing, we agreed on a protocol to relate biopsies from the 1-year follow-up to the clinical prognosis at 5 years, and with meticulous quality control of all biopsy material.¹³ This work supplemented the IBSEN database, for the study itself as well as for all future collaborations.

During the 4-year inclusion period, 45% of 843 IBSEN patients were included in the EC database. By the 1-year follow-up, migration rate and population stability were confirmed in all Southeastern Norway counties covered by the IBSEN study. Emphasis was put on extraintestinal manifestations, health-related quality of life, and molecular biology, for dissertations covering the first 5 years of follow-up and for the overall progress of the IBSEN group.^20,21

Progress of the EC study and IBSEN study during the first 10 years

A separate 5-year follow-up focused on specific clinical problems in the IBSEN study, aiming to demonstrate disease course, activity markers, and diagnostic stability within the first 5 years of the IBSEN cohort.^21–27 International interest in disease activity markers, specifically the serologic marker CRP, stimulated discussion. Building on its established application in Europe and the IBSEN study (since 1990), CRP’s utility as a clinical marker garnered recognition in the USA. A 2004 meeting in New York, convening experts from Europe and North America, resulted in a consensus to prioritize CRP in forthcoming international studies. Subsequently, the IBSEN group presented their findings at Digestive Disease Week (DDW, US), which led to a well-received publication.²⁸ A 5-year follow-up was also conducted on the pediatric IBSEN study as a continuation of the initial pediatric incidence study.²⁹

Results from the first 10 years of follow-up were partly presented as part of the EC-IBD project, and in parallel Norwegian IBSEN data collection was continued. The 10-year follow-up of UC in EC-IBD compared the incidence and clinical course of UC based on data from the European consortium of Northern and Southern European centers. Studies of the combined EC-IBD and IBSEN material included findings on extraintestinal manifestations and on risk of thromboembolism in IBD.^30,31

The IBSEN study’s 10-year follow-up on UC and CD presented clinical data.^32,33 Close follow-up and good compliance with medical treatment was shown to yield reduced recurrence rate, even before biologics therapy was available. Notably, these articles highlighted four prospectively recorded patterns of disease course in UC and CD (Figure 3). Similar clinical patterns have been observed in IBD associated with liver disease, as well as in colitis activity following transplantation and immunosuppression.^34,35 It also provided original population-based data on ASCA and pANCA as prognostic factors, based on collaboration with the Leuven laboratory.³⁶ Furthermore, predictive risk matrices were developed for UC and CD, based on combined serological markers, demographic and clinical data, considering steroid treatment at diagnosis.^37,38

Figure 3.

Patient-reported bowel symptom severity from diagnosis to 10-year follow-up. (a) Ulcerative colitis, n = number of non-operated patients reporting and (b) CD illustrates four predefined curves representing patient-reported bowel symptom severity from diagnosis to 10-year follow-up.

In the IBSEN cohort, patient-reported quality of life (PRO) was evaluated at the 10-year follow-up to determine its association with work disability. This study yielded novel insights relevant to personalized treatment strategies and prognostic assessment, extending beyond traditional measures of disease activity. The findings significantly contributed to international research in this area and served as a basis for further studies in Norway.^39–42

Combining the IBSEN study with research projects outside the IBSEN study group

The IBSEN study has yielded several publications as spinoff to the initially planned research fields. These include studies on geographic clustering^43,44 and the combined effects of temperature and latitude using Norwegian registries.⁴⁵ Familial relationships in IBD were examined within the IBSEN cohort, providing further insight into familial anticipation in CD. This study is of international interest due to its population-based design and substantial sample size.⁴⁶ In the research of the use of complementary and alternative medicine in IBD, an emerging field, the IBSEN data have contributed to subsequent national and international studies.⁴⁷

A subsequent population-based cohort study in Norway (IBSEN II, 2005–2007), conducted in the same geographic region, revealed a significant rise in the incidence of IBD among children compared to the initial IBSEN study performed 15 years prior.⁴⁸

The 20-year follow-up of the IBSEN study

In the early 2000s, a thorough 20-year follow-up study of the IBSEN cohort was decided, including further clinical, demographic, and familial information.

The follow-up study reported on mortality rates, overall incidence of malignancy, and clinical outcomes at follow-up in UC patients, in addition to assessing quality of life, including fatigue, in relation to long-standing IBD.^49–55

The inclusion of magnetic resonance imaging yielded new insights into particularly the population-based prevalence of PSC in IBD.^56,57

Follow-up studies on arthritis and spondylitis in long-standing IBD explored relationships to HLA and genetic predisposition.^58–60

Markers of colorectal malignancy in stool samples were investigated, upon agreement with colleagues at the Mayo Clinic, and in collaboration with the Mayo group.^61,62

Based on the results of the EC-IBD and IBSEN studies, identifying antibodies as prognostic markers, Prometheus Laboratories suggested in 2009 an expanded antibody panel for prognostic studies of the IBSEN material.⁶³

The most recent study was a 30-year register-based follow-up study (2020–2024) examining cause-specific mortality and malignancies among patients in the IBSEN cohort.^64–67 This study largely focused on aging among IBD patients (Figure 4). This suggests effective medical care in mitigating risks associated with IBD, particularly on the risk of CRC.

Figure 4.

Forest plot of mortality in selected recent ulcerative colitis studies (a) and Crohn’s disease studies (b) The first reference Follin-Arbelet et al. (2022) is from the IBSEN study⁶⁵ and the figures published in a PhD Thesis at UiO.⁶⁷

The network of gastroenterologists in the IBSEN study

The success of the IBSEN study has relied on the dedication of local gastroenterologists and the GPs’ support for research. Patient confidence and compliance were crucial, as well. The skills of nurses, attendants, and lab assistants at each center were essential. Maintaining this network requires ongoing collaboration and strong central leadership, which was essential for data quality and collaboration among key personnel.

The IBSEN participants gratefully acknowledge the invaluable contributions of the statisticians. Their expertise and profound understanding of the IBSEN database, coupled with their exceptional dedication to each PhD candidate, were instrumental to the study’s success, outcomes, and scientific merit.

From the outset of the study, pathologists have offered critical expertise in protocol development and data interpretation. Initial funding was secured through the EC-IBD’s EU funding program; however, the engagement of medical industry representatives, providing funding for specific research initiatives, has proven vital to the successful execution of numerous projects. Our collaboration with industry partners has grown substantially since the introduction of biologic therapies.

The past and the future, nationally and internationally

The IBSEN study the collection of clinical and epidemiological data from Norwegian IBD patients, offering the potential for an extensive, lifelong characterization of IBD with increasing number of person-years and events. National registers, containing information on hospitalization, prescriptions, socioeconomic factors, and specific disease details, enabled collaborative nationwide studies.⁶⁸ These registers also allowed linking IBSEN data with medical and non-medical information, potentially compensating for challenges in collecting individual data. While repeated clinical examinations or patient-reported outcomes offer precise insights in disease evolution, they demand significant resources, even with fewer participating patients. The IBSEN study served as an exploratory platform, delineating future research avenues. Subsequent investigations could refine findings, such as determining the incidence of cardiovascular disease and related mortality or incorporating relevant variables like cancer risk factors. The IBSEN study’s experience was crucial for initiating new studies, including the IBSEN II study, and for developing the EU-sponsored IBD Character multicenter study.^69,70

A new successor to IBSEN, the IBSEN III study was initiated in 2017. IBSEN III applied the same design and diagnostic criteria as the original IBSEN study, to ensure comparability, but also increased the geographical catchment area to the whole Southeastern health region (covering 3 million inhabitants, that is, half the Norwegian population), including comprehensive clinical and PRO data from the start as well as a large biobank.⁷¹ The new opportunities for IBSEN III, compared to the original IBSEN study, will be that all expected achievements, many of them based on experience from the IBSEN study, have been systematically planned from the start. Further, IBSEN III can link clinical data to nationwide registry data. Of special importance is the national patient registry, established in 2004, enabling quality assurance of patients’ affiliation to community, which largely makes the primary briefing of general practitioners superfluous, as to several epidemiological and geographical questions. The utilization of national expertise in molecular biology, coupled with collaborations with national and international experts possessing extensive experience in various fields of IBD and translational research, has significantly advanced.⁷²

Addendum

Over the past three decades, the IBSEN study has demonstrated significant progress, underscoring the critical roles of both individual decision-making and collective participation. Clinical science has advanced substantially during this period, driven by increased societal recognition. However, growing institutionalization and stringent regulations may potentially impede individual scientific creativity. The IBSEN group has successfully adapted to evolving national and international standards. While institutions and registries are increasingly essential, they remain reliant on the sustained commitment of individuals within large collaborative research endeavors. We posit that replicating the IBSEN consortium’s database within a hospital setting or national registry would have been challenging without a legal mandate akin to that of the National Cancer Registry. Despite a societal inclination toward institutional ownership of projects and data, to ensure responsibility for the patients, the IBSEN group maintains that the intellectual integrity and collaborative ethos of researchers dedicated to patient welfare and responsible data management have been the cornerstone of the project. This patient-centered approach, combined with the active engagement of patients, has been pivotal to the success of the IBSEN study.

Footnotes

Acknowledgements

None.

Declarations

ORCID iD

Bjørn Moum

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