Incidence of inflammatory bowel disease in the province of Styria, Austria, from 1997 to 2007: A population-based study

Background The incidence of inflammatory bowel disease (IBD) varies widely between different countries. This large variation is also observed for the incidence of its main two forms, ulcerative colitis (UC) and Crohn's disease (CD). Controversy exists whether IBD incidence is increasing, especially in western countries. Currently no data are available for Austria. This study therefore aimed to evaluate for the first time the incidence of IBD over an eleven-year period in Styria, a province of Austria with a population of 1.2million. Methods All patients with an initial diagnosis of IBD between 1997 and 2007, who were Styrian residents, were eligible for this retrospective study. Data were acquired from electronically stored hospital discharge reports and individual reports by patients and physicians. According to population density Styria was divided into two rural and one urban area. Results Throughout the study period 1527 patients with an initial diagnosis of IBD were identified. The average annual incidence was 6.7 (95% CI 6.2–7.1) per 100,000 persons per year for CD and 4.8 (95% CI 4.5–5.2) for UC. The average annual incidence increased significantly (p<0.01) for both diseases during the 11year study period. Median age at initial diagnosis was 29years (range 3–87) for CD and 39years (range 3–94) for UC. At diagnosis, 8.5% of all IBD patients were <18years of age. The incidence of both CD and UC was significantly higher in the urban area than in rural areas (CD: 8.8, 95% CI 7.8–9.8 versus 5.5, 95% CI 4.7–6.4 and 5.9, 95% CI 5.3–6.7; [p<0.001]; UC: 5.8, 95% CI 5.1–6.6 versus 4.0, 95% CI 3.4–4.7 and 4.7, 95% CI 4.1–5.4; [p=0.04]). Conclusion We observed an overall increase in the incidence of ulcerative colitis and Crohn's disease in a part of Austria during an eleven year period. IBD was more predominant in the largest urban area than in rural areas.