Increasing Incidence of Inflammatory Bowel Disease, with Greatest Change Among the Elderly: A Nationwide Study in Finland, 2000-2020

Background and Aims The incidence of inflammatory bowel disease [IBD] is stabilising in many Western countries. Some still show increasing incidence. Our objective was to determine the latest trends in IBD incidence and prevalence in Finland and to compare these among different age groups and between different geographical areas. Methods We used the nationwide registry of the Social Insurance Institute of Finland to identify new IBD cases during the period 2000-2020. Crude, age-specific, and age-standardised incidence rates were calculated. Prevalence was estimated using valid reimbursements from the same database in 2000-2020. Results We identified 42 498 new IBD cases. The crude annual incidence increased in ulcerative colitis [UC] from 20 to 35 (incidence date ratio [IRR] 1.03, 95% confidence interval [CI] 1.02-1.03), in Crohn's disease [CD] from 8 to 13 [IRR 1.02, CI 1.02-1.03] and in IBD overall from 28 to 48 per 100 000 person-years [IRR 1.02, CI 1.02-1.03]. Men had higher incidence than women in UC, but in CD the incidences were equal. The incidence of IBD increased in all age groups except for small children. The increase in both UC and CD was most marked among the elderly aged over 70. A north-south gradient was discernible. The crude prevalence of IBD increased from 376 to 972 per 100 000 (prevalence rate ratio [PRR] 1.05, CI 1.05-1.05). Conclusions The incidence of IBD, UC, and CD is increasing in Finland. The increase is most notable in the elderly. Current prevalence of IBD is 1%.