Epidemiological Trends in Inflammatory Bowel Disease in Korea: Age-Related Shifts and Urban-Rural Disparities in a Nationwide Study, 2004-2015

Abstract

Purpose: The incidence of inflammatory bowel disease (IBD) is rapidly increasing in newly industrialized Asian countries. However, nationwide epidemiological shifts, especially age-specific trends and urbanization effects, remain unclear in Korea. This study aimed to define recent secular trends in IBD incidence by age and residential area using the Korean National Health Insurance database. Materials and Methods: We conducted a nationwide, population-based study using claims data from the National Health Insurance Service from 2004 to 2015. IBD cases were defined by a combination of diagnostic codes for Crohn's disease (CD) or ulcerative colitis (UC) and relevant prescription records. Age-standardized incidence rates (ASRs) were calculated, and joinpoint regression was used to estimate annual percent changes (APCs). Standardized incidence ratios (SIRs) compared incidence between metropolitan and non-metropolitan areas. Results: A total of 15241 CD and 39028 UC patients were identified. ASRs for both CD and UC steadily increased during the study period, with APCs of 6.8% [95% confidence interval (CI): 5.8-7.8] for CD and 3.2% (95% CI: 2.6-3.8) for UC. CD incidence was highest among adolescents aged 15-19 years. For UC, the peak age of onset shifted from 55-69 years in 2004 to 20-39 years by 2015. The most dramatic rise in UC incidence occurred in the 10-19 age group. Metropolitan areas had higher incidence rates than nonmetropolitan areas for both diseases. Conclusion: The epidemiology of IBD in Korea is rapidly evolving, with increasing incidence, younger onset, and an urban-rural divide. Targeted strategies for adolescents and urban populations are needed.