Incidence, prevalence and clinical outcome of anaemia in inflammatory bowel disease: a population-based cohort study

Background The incidence and short-term outcome of anaemia in inflammatory bowel disease (IBD) are largely unknown. Aim To determine the incidence, prevalence and clinical outcome of anaemia in terms of resolution of anaemia within 12months. We also planned to assess risk factors for anaemia in IBD. Methods A random sample of 342 patients was obtained from the population-based IBD cohort of orebro University Hospital, Sweden, consisting of 1405 patients diagnosed between 1963 and 2010. Haemoglobin measurements recorded from 1 January 2011 to 31 December 2013 were extracted from the Clinical Chemistry data system. Results In Crohn's disease, the incidence rate of anaemia was 19.3 (95% CI: 15.4-23.7) per 100 person-years and the prevalence was 28.7% (CI: 22.0-36.2), compared with 12.9 (CI: 9.8-16.5) and 16.5% (CI: 11.2-22.9) for ulcerative colitis. Crohn's disease was associated with an increased incidence (OR=1.60; CI: 1.02-2.51) and prevalence of anaemia (OR=2.04; CI: 1.20-3.46) compared to ulcerative colitis. Stricturing disease phenotype in Crohn's disease (HR=2.59; CI: 1.00-6.79) and extensive disease in ulcerative colitis (HR=2.40; CI: 1.10-5.36) were associated with an increased risk of anaemia. Despite a higher probability of receiving specific therapy within 3months from the diagnosis of anaemia, Crohn's disease patients had a worse outcome in terms of resolution of anaemia within 12months (56% vs 75%; P=0.03). Conclusions Anaemia is a common manifestation of IBD even beyond the first years after the diagnosis of IBD. Crohn's disease is associated with both an increased risk and a worse outcome.