title: Association between Helicobacter pylori infection and inflammatory bowel disease: a meta-analysis and systematic review of the literature.
abstract: BACKGROUND
  Epidemiologic data suggest a protective effect of Helicobacter pylori infection against the development of autoimmune disease. Laboratory data illustrate H. pylori's ability to induce immune tolerance and limit inflammatory responses. Numerous observational studies have investigated the association between H. pylori infection and inflammatory bowel disease (IBD). Our aim was to perform a systematic review and meta-analysis of this association.
  
  
  METHODS
  Medline, EMBASE, bibliographies, and meeting abstracts were searched by 2 independent reviewers. Of 369 abstracts reviewed, 30 promising articles were reviewed in detail. Twenty-three studies met our inclusion criteria (subject N = 5903). Meta-analysis was performed with the metan command in Stata 10.1.
  
  
  RESULTS
  Overall, 27.1% of IBD patients had evidence of infection with H. pylori compared to 40.9% of patients in the control group. The estimated relative risk of H. pylori infection in IBD patients was 0.64 (95% confidence interval [CI]: 0.54-0.75). There was significant heterogeneity in the included studies that could not be accounted for by the method of IBD and H. pylori diagnosis, study location, or study population age.
  
  
  CONCLUSIONS
  These results suggest a protective benefit of H. pylori infection against the development of IBD. Heterogeneity among studies and the possibility of publication bias limit the certainty of this finding. Further studies investigating the effect of eradication of H. pylori on the development of IBD are warranted. Because environmental hygiene and intestinal microbiota may be strong confounders, further mechanistic studies in H. pylori mouse models are also necessary to further define the mechanism of this negative association.
authors.affiliation: University of Michigan Medical Center, Ann Arbor, Michigan, USA. jayluthe@umich.edu
authors.forename: Jay
authors.initials: J
authors.lastname: Luther
authors.forename: Maneesh
authors.initials: M
authors.lastname: Dave
authors.forename: Peter D R
authors.initials: PD
authors.lastname: Higgins
authors.forename: John Y
authors.initials: JY
authors.lastname: Kao
mesh_terms: D000818:Animals; D005260:Female; D016481:Helicobacter Infections / Q000276:immunology*; D016480:Helicobacter pylori / Q000276:immunology*; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000453:epidemiology* / Q000276:immunology*; D008297:Male; D051379:Mice; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D014481:United States / Q000453:epidemiology