Crohn's disease (CD) and ulcerative colitis (UC) are considered rare diseases in developing countries. We have evaluated the incidence and prevalence of CD and UC over time in a district of Seoul, Korea. A population-based study was performed from 1986 to 2005 in the Songpa-Kangdong district of Seoul. To recruit patients as completely as possible, multiple information sources, including all medical facilities in the study area and 3 referral centers nearby but outside the study area, were used. During the 20-year study period, 138 incident cases of CD (102 men, 36 women) and 341 incident cases of UC (170 men, 171 women) were identified. For the 20-year period, the adjusted mean annual incidence rates of CD and UC per 100,000 inhabitants were 0.53 (95% CI 0.44-0.62) and 1.51 (95% CI 1.34-1.67), respectively. When analyzed by 5-year intervals, the mean annual incidence rates of CD and UC increased significantly, from 0.05 and 0.34 per 100,000 inhabitants, respectively, in 1986-1990 to 1.34 and 3.08 per 100,000 inhabitants, respectively, in 2001-2005. The adjusted prevalence rates of CD and UC per 100,000 inhabitants on December 31, 2005, were 11.24 (95% CI 9.29-13.18) and 30.87 (95% CI 27.47-34.27), respectively. The incidence and prevalence of CD and UC in Seoul, Korea, are still low compared with those in Western countries, but are rapidly increasing.
