title: Systematic review of the epidemiological evidence on Helicobacter pylori infection and nonulcer or uninvestigated dyspepsia.
abstract: BACKGROUND
  Previous studies have yielded conflicting results and substantial uncertainty about any independent association of Helicobacter pylori infection with dyspepsia, and about any benefits of antibiotic treatments for nonulcer or uninvestigated dyspepsia.
  
  
  OBJECTIVE
  To perform a systematic review of the literature to determine whether chronic infection with H pylori is relevant to nonulcer or uninvestigated dyspepsia.
  
  
  METHODS
  Observational studies of associations between H pylori and dyspepsia published before April 1999 and randomized trials of the effects of H pylori eradication on dyspepsia published before January 2000 were identified by computer-assisted literature searches of relevant journals, reference lists, and discussions with authors. Relevant data were abstracted from the published reports by 2 investigators according to a fixed protocol.
  
  
  RESULTS
  Thirty relevant observational studies were identified involving approximately 3392 patients with nonulcer dyspepsia, and 11 separate observational studies were identified, involving 6426 patients with uninvestigated dyspepsia. Reports of strong associations in small observational studies without appropriate adjustment for potential confounding factors were not generally confirmed by larger and better-designed studies. No studies have been reported, however, that can reliably confirm or exclude the existence of any weak associations. Twenty-two randomized trials of treatments against H pylori were found involving a total of 2340 patients with nonulcer dyspepsia, almost all with positive H pylori test results. Only a few of these trials involved effective antibacterial regimens with prolonged follow-up, and even these studies were too small to assess the possibility of moderate benefits.
  
  
  CONCLUSIONS
  The available evidence indicates that there is no strong association between H pylori and dyspepsia, but there is insufficient evidence to confirm or refute the existence of a modest association.
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, England.
authors.forename: J
authors.initials: J
authors.lastname: Danesh
authors.forename: M
authors.initials: M
authors.lastname: Lawrence
authors.forename: M
authors.initials: M
authors.lastname: Murphy
authors.forename: S
authors.initials: S
authors.lastname: Roberts
authors.forename: R
authors.initials: R
authors.lastname: Collins
mesh_terms: D002908:Chronic Disease; D004415:Dyspepsia / Q000209:etiology / Q000382:microbiology*; D016481:Helicobacter Infections / Q000150:complications* / Q000188:drug therapy; D016480:Helicobacter pylori; D006801:Humans