title: Prevalence of anemia in inflammatory bowel diseases in european countries: a systematic review and individual patient data meta-analysis.
abstract: 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.
authors.affiliation: *Institute of Biostatistics and Mathematical Modeling, Faculty of Medicine, and †Department of Internal Medicine 1, Goethe-University Hospital, Frankfurt, Germany; ‡IBD Unit, Chair of Gastroenterology, L. Sacco University Hospital, Milan, Italy; §Department of Medicine V (Hepatology and Gastroenterology), Aarhus University Hospital, Aarhus, Denmark; ‖Dip. Area Medica: Medicina Generale 1, Policlinico San Matteo, Pavia, Italy; ¶Department of Gastroenterology, University Hospital Heraklion, Crete, Greece; **Department of Gastroenterology, University Hospital Skane, Malmö, Sweden; ††Sección de Aparato Digestivo, Hospital Infanta Cristina, Parla, Madrid, Spain; ‡‡Department of Gastroenterology, Oslo University Hospital, Oslo, Norway; and §§Division of Gastroenterology, Triemli Hospital, Zurich, Switzerland.
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mesh_terms: D000740:Anemia / Q000453:epidemiology* / Q000209:etiology; D005060:Europe / Q000453:epidemiology; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000150:complications*; D015995:Prevalence; D011379:Prognosis