Inflammatory Bowel Disease Incidence is on the Continuous Rise Among All Paediatric Patients Except for the Very Young: A Nationwide Registry-based Study on 28-Year Follow-up

Background and Aims: The burden of inflammatory bowel disease [IBD] in health care is high. We conducted research on the temporal changes in the incidence of paediatric IBD [PIBD] using nationwide registry-based data in Finland. Methods: All PIBD cases diagnosed at less than 20 years of age during 1987-2014 [in total, 5415 patients] were retrieved from a database documenting reimbursements for drug costs. Incidence rates were calculated by dividing the number of annual new PIBD cases by the size of the paediatric population at risk during each calendar year. Temporal trends in the incidences of PIBD and its subtypes, ulcerative colitis [UC] and Crohn's disease [CD], were estimated using Poisson regression analyses. Results: The mean annual incidence of PIBD increased from 7/100 000 for the years 1987-1990 to 23/100 000 for the years 2011-2014. The average rate of increase was 4.1% (95% confidence interval [CI]: 3.6-4.5) per annum. In the period 2000-2014, the increase rate in the annual incidence of UC [3.8%; 95% CI: 2.7-5.0], was steeper than for CD [2.5%; 95% CI: 1.0-3.8]. The most pronounced increase occurred in UC among adolescents aged 16-19 years [4.8%; 95% CI: 2.9-6.7]. For children less than 10 years of age, the rate of change remained low. Approximately 0.17% of the birth cohort for the years 1999-2000 was diagnosed with PIBD by the age of 14 years. Conclusion: The incidence of PIBD is primarily increasing among adolescents, challenging the identification of the possible environmental triggers for the disease.