Abstract
Background: Industrialization, urbanization, and westernization have been associated with rising incidence and prevalence of inflammatory bowel disease (IBD) across time and geog- raphy. Epidemiologic trends are categorized into stages of IBD evolution: Stage 1, Emergence, is marked by low incidence and prevalence; stage 2, Acceleration in Incidence, is marked by rapidly rising incidence and low prevalence; and stage 3, Compounding Prevalence, is marked by stabilizing incidence and rapidly rising prevalence. However, the societal drivers underlying transitions across the three epidemiologic stages of IBD are poorly understood.
Aim: To explore societal indicators influencing changes in the incidence and prevalence of IBD across three epidemiologic stages.
Methods: Epidemiologic stage classifications were previously determined using data from a systematic review of 522 population-based studies on IBD incidence and prevalence (1920-2024), which informed a machine learning model that classified countries into stage 1, stage 2, or stage 3. Five time- and region-specific societal indicators were examined: the Augmented Human Development Index (AHDI), obesity rate, percent urbanization, the Universal Health Coverage (UHC) Service Index, and the Western Diet Index (WDI) (Table 1). Obesity, urbanization, and WDI data were available annually; annual values for AHDI and UHC were derived using inner-linear interpolation of data originally available in five-year increments. Kruskall-Wallis tests assessed the relationship between each of the five societal indicators and the three epidemiologic stages. Effect sizes (η²), representing the strength of association between the epidemiologic stages and each societal indicator (where η²≥0.14 indicates a robust association), were calculated to quantify the proportion of total variance in a societal indicator attributed to each epidemiologic stage. Post hoc pairwise comparisons between stages were performed using Wilcoxon rank-sum tests with a Holm adjustment for multiple comparisons.
Results: All five societal indicators differed significantly across the three epidemiologic stages (p<0.001). Median values for all indicators progressively increased across stages, reflecting societal shifts aligned with AHDI, obesity rate, percent urbanization, UHC, and WDI measures as global regions transition across stages (Figure 1). Among the indicators, AHDI showed the strongest association with stage classification (η²=0.452) (Table 1).
Discussion: Societal indicators provide valuable insights into the rising global burden of IBD as regions undergo economic growth, healthcare advancements, and lifestyle changes. The AHDI, in particular, can serve as a reliable proxy measure to predict epidemiologic stages in regions with limited population-based data on the incidence and prevalence of IBD.