Abstract
Background
Incidence and prevalence of inflammatory bowel diseases (IBD) have been increasing for the past decades in the western world, however with an emerging trend of incidence stabilisation in recent years. There is an indication of higher IBD incidence and prevalence in northern Europe, especially in the Nordic region, compared with southern Europe.
Methods
This retrospective observational study collected data from the National Patient Registries and National Prescription Registries (Sweden [SWE], Norway [NOR], Denmark [DEN]) and one university hospital database (Turku, Finland [FIN]) during 2010–2017 to investigate the annual incidence and prevalence of ulcerative colitis (UC) and Crohn’s disease (CD). Patients with ≥2 ICD-10 diagnosis codes for UC (K51) or CD (K50) from 2010 or later and no K51 or K50 codes prior to 2010 were included; patients were classified according to their last code. The look-back period for SWE was until 2000, for NOR until 2008, for DEN until 1995, and for FIN until 2004. Incidence proportions highlight results through 2016, as 2017 patients had less than 1-year follow-up.
Results
In total, 69,876 patients were included (SWE n = 27,902, NOR n = 20,761, FIN n = 2,118, DEN n = 19,095), of which 44 367 patients were diagnosed with UC and 25,509 with CD. In 2016, the annual incidence of UC was 28 patients per 100,000 persons in NOR, 32 patients per 100,000 persons in DEN, 25 patients per 100,000 persons in SWE, and 44 patients per 100,000 in FIN. The corresponding results for the annual incidence of CD per 100,000 persons were 22 in NOR, 16 in DEN, 16 in SWE, and 21 in FIN. The prevalence per 100,000 persons of both UC and CD was the highest in DEN, followed by SWE and NOR, and lowest in FIN. Prevalence estimates increased in all four Nordic countries during 2010–2017: for UC, from 409 to 488 patients in SWE, from 256 to 428 in NOR, from 129 to 375 in FIN, and from 577 to 798 in DEN. For CD, it increased from 261 to 313 patients in SWE, from 164 to 258 in NOR, from 54 to 164 in FIN, and from 280 to 400 in DEN.
Conclusion
This retrospective observational study showed that during 2016, the annual incidence of UC ranged from 25–44 patients per 100,000 persons across the evaluated Nordic countries, whereas the annual incidence of CD was 16–22 patients per 100,000 persons. Prevalence of both UC and CD increased during 2010–2017 in all four countries. Estimates of UC and CD incidence and prevalence in this analysis are greater than reported in the published literature. Additional analyses are underway to further explore the impact of methodological decisions on the estimates of UC and CD annual incidence and prevalence.
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