Abstract
Background: The prevalence of inflammatory bowel disease (IBD) has steadily increased in North America, Europe, and Oceania, driven by a phenomenon called compounding prevalence, which, together with stabile incidence, characterizes the 3rd epidemiologic stage of IBD evolution. Comprehensive analyses of population-based epidemiologic surveillance data from stage 3 countries remain limited.
Aim: To estimate IBD incidence and prevalence in 2025 among countries in the 3rd epidemiologic stage by forecasting historical temporal data.
Methods: Population-based administrative data on IBD incidence / prevalence were acquired from Canada (2002-2014); Catalonia (2011-2020); Denmark (1990-2017); Veszprém, Hungary (2002-2018); Israel (2005-2020); Canterbury, New Zealand (2018-2023); Lothian, Scotland (2009-2017); Sweden (1990-2014); and Olmsted County, USA (1990-2020). Rates were age- and sex-standardized to the matching year of the Canadian population. Incidence and prevalence (per 100,000) of individual countries were forecast to 2025 using autoregressive integrated moving average models, with associated 95% prediction intervals (P1). Overall incidence (2007-2020) and prevalence (2005-2020) were calculated with weighted (by country population) meta-analysis of country-specific standardized rates. For countries lacking complete historical data to match the start year, standardized rates were estimated through historical forecasting. The overall forecasted rates and 95% Pis to 2025 were calculated using weighted meta-analysis of country-specific forecasted rates and their 95% Pls. Average annual percentage change (AAPC), with 95% confidence intervals (CI), were calculated using Poisson or negative binomial models.
Results: Overall, IBD prevalence is forecast to significantly increase by 2.80% annually (95%C1:2.56, 3.03), reaching an estimated prevalence of 0.89% (95%CI: 0.86, 0.92) by 2025. Prevalence in all countries is forecast to significantly increase, with AAPCs ranging from 1.00% (9 5 % CI: 0.57, 1.43) in the USA to 4.85% (95%CI: 4.67, 5.02) in Catalonia. By 2025, prevalence is forecast to range from 616 per 100,000 (95%CI: 604, 629) in the USA to 1,179 per 100,000 (95%CI: 1133, 1226) in Denmark. The overall incidence rate is forecast to remain stable (AAPC: 0.65%; 95%C1: -1.41, 2.12) at 34.7 per 100,000 (95%PI: 27.5, 42.0) in 2025. Incidence trends vary by country: Rates are forecast to decrease in Israel; remain stable in Canada, Scotland, Catalonia, Hungary, Sweden, and New Zealand; and increase in Denmark and USA.
Discussion: By 2025, the prevalence of IBD is projected to rise to 0.889% across countries within the 3rd epidemiologic stage, while incidence remains stable at 34.7 per 100,000. The compounding prevalence effect highlights the growing strain on healthcare systems and the urgent need for strategic action to ensure sustainable long-term care.