Ulcerative colitis in Olmsted County, Minnesota, 1940-1993: incidence, prevalence, and survival

Background-There is significant geographic variation in the reported incide nce of ulcerative colitis. Aims-To update the incidence and prevalence of ulcerative colitis in Olmste d County, Minnesota, examine temporal trends, and determine overall surviva l. Patients-Ah Olmsted County residents diagnosed with ulcerative colitis betw een 1940 and 1993 (incidence cases), and all residents with ulcerative coli tis alive on 1 January 1991 (prevalence cases). Methods-Incidence and prevalence rates were adjusted using 1990 US census f igures for whites. The effects of age, sex, and calendar year on incidence rates were evaluated using Poisson regression. Survival from diagnosis was compared with that expected for US north-central whites. Results-Between 1940 and 1993, 278 incidence cases were identified. for an adjusted incidence rate of 7.6 cases per 100 000 person years (95% confiden ce interval (CI), 6.7 to 8.5). On 1 January 1991, there were 218 residents with definite or probable ulcerative colitis, for an adjusted prevalence ra te of 229 cases per 100 000 (95% CI, 198 to 260). Increased incidence rates were associated with later calendar years (p<0.002), younger age (p<0.0001 ), urban residence (p<0.0001), and male sex (p<0.003). Overall survival was similar to that expected (p>0.2). Conclusions-The overall incidence rate of ulcerative colitis in Olmsted Cou nty increased until the 1970s, and remained stable thereafter. Incidence ra tes among men and urban residents were significantly higher. The prevalence rate in Rochester in 1991 was 19% higher than that in 1980. Overall surviv al was similar to that of the general population.