BACKGROUND
The rising incidence of inflammatory bowel disease (IBD) globally has increased disease burden and economic impact. Gaps remain in understanding the IBD burden between Asian and Western populations. AIM To estimate the current and following 10-year prevalence and incidence of IBD in Hong Kong, Japan, and the United States.

METHODS

Patients diagnosed with IBD were identified from a territory-wide electronic medical records database in Hong Kong (2003-2022, including all ages) and two large employment-based healthcare claims databases in Japan and the United States (2010-2022, including < 65 age). We used Autoregressive Integrated Moving Average models to predict prevalence and incidence from 2023 to 2032, stratified by disease subtype [ulcerative colitis (UC); Crohn’s disease (CD)], sex, and age, with 95% prediction intervals (PIs). The forecasted annual average percentage change (AAPC) with 95% confidence intervals was calculated.

RESULTS
The age-standardized prevalence of IBD for 2032 is forecasted at 105.88 per 100000 in Hong Kong (95%PI: 83.01-128.75, AAPC: 5.85%), 645.79 in Japan (95%PI: 562.51-741.39, AAPC: 5.78%), and 629.85 in the United States (95%PI: 569.09-690.63, AAPC: 2.85%). Prevalence is estimated to rise most significantly among those under 18 in Japan and the United States. Over the next decade, the incidence of IBD is estimated to increase annually by 3.3% in Hong Kong with forecasted increases across all age groups (although the AAPC for each group is not statistically significant); by 2.88% in Japan with a significant rise in those under 18 and stability in 18-65; and remaining stable in the United States. By 2032, the prevalence of CD is estimated to surpass UC in Hong Kong and the United States, whereas UC will continue to be more prevalent in Japan. A higher prevalence and incidence of IBD is forecast for males in Hong Kong and Japan, whereas rates will be similar for both males and females in the United States.

CONCLUSION
The prevalence of IBD is forecasted to increase in Hong Kong, Japan, and the United States, while estimates of incidence vary. The forecasts show distinct patterns across disease subtype, sex, and age groups. Health systems will need to plan for the predicted increasing prevalence among different demographics.