A nationwide cohort study of the incidence of inflammatory bowel disease in Sweden from 1990 to 2014

Abstract

BACKGROUND: Epidemiological studies have shown inconsistent incidence rates (IRs) for inflammatory bowel disease (IBD). AIM: To assess the incidence and temporal trends of IBD in Sweden. METHODS: Nationwide cohort study based on diagnostic codes for IBD and biopsy reports registered through the ESPRESSO cohort in 1990-2014. Age-specific and age-standardised IRs and cumulative incidence were calculated. RESULTS: Overall, we identified 65 908 cases of incident IBD: ulcerative colitis (UC, n = 38 261, 58%), Crohn's disease (CD, n = 18 577, 28%) and IBD-U (n = 9070, 14%). During 1990-2014, the overall IRs per 100 000 person-years were 29.0 (95% CI: 27.3-30.7) for IBD, 16.9 (15.9-17.9) for UC, and 8.1 (7.7-8.6) for CD. For IBD-U, the IR was 5.2 (4.9-5.6) in 2002-2014. The annual incidence of IBD, UC and CD increased by approximately 7% per year between 1990 and 2001 (P < 0.001) and then decreased by 1%-2% per year from 2002 onwards (P < 0.001). IRs for IBD, UC and IBD-U were higher in males while the IR for CD was higher in females. The lifetime risk of IBD was about 2.5% for both sexes. CONCLUSIONS: In Sweden, the incidence of IBD in all subtypes increased in 1990-2001 but has since declined. One in 40 individuals is expected to be diagnosed with IBD during their lifetime.