Prevalence of Anemia in Inflammatory Bowel Diseases in European Countries: A Systematic Review and Individual Patient Data Meta-analysis

Background: The main objective is to determine the overall prevalence of anemia in inflammatory bowel diseases (IBD) in Europe. Methods: A systematic literature search in PubMed and Embase was performed for studies published between January 2007 and May 2012. Eligible studies were included if they were original full-paper publications originated from Europe and if the authors agreed to provide their data. An overall prevalence of anemia in IBD, disease specific, and age-gender stratified basis prevalences were estimated. The influence of disease entity (Crohn's disease/ulcerative colitis), gender, age, disease activity (remission/active disease), and IBD-specific treatment strategies on the prevalence of anemia was analyzed by a mixed logistic regression model. Thereby, the factor country of origin was included as a random effect. Results: Data were available for 2192 patients, mainly treated in tertiary referral centers. The overall prevalence of anemia in IBD patients was 24% (95% confidence interval, 18-31). Age-gender stratified prevalences were estimated for the age strata 18 to 29, 30 to 39, 40 to 49, 50 to 64, 65 to 74, >74 years and ranged from 18% to 35%. Patients receiving IBD-specific medication (P = 0.0002, odds ratio 1.54), and patients with active disease status (P < 0.0001, odds ratio 2.72) were significantly more likely to have anemia compared with patients not receiving IBD-specific medication or being in remission. Patients with ulcerative colitis tended to have anemia less likely than patients with Crohn's disease (P = 0.01, odds ratio 0.77). Conclusions: The overall prevalence of anemia in patients with Crohn's disease was 27% (95% confidence interval, 19-35) and 21% (95% confidence interval, 15-27) in patients with ulcerative colitis. Thereby, 57% of the anemic patients were iron deficient.