title: Are genetic influences on peptic ulcer dependent or independent of genetic influences for Helicobacter pylori infection?
abstract: BACKGROUND
  Genetic factors play a role or roles in the etiology of peptic ulcer disease and the acquisition of Helicobacter pylori infection.
  
  
  OBJECTIVE
  To evaluate the relative importance of genetic and environmental influences as well as the importance of H. pylori on peptic ulcer disease.
  
  
  METHODS
  Cross-sectional study on monozygotic (MZ) and dizygotic (DZ) twins, reared apart or together.
  
  
  METHODS
  Twins of the subregistry of the Swedish Twin Registry included in the Swedish Adoption/Twin Study of Aging.
  
  
  METHODS
  Peptic ulcer disease and H. pylori status were assessed in MZ and DZ twin pairs reared apart or together. A total of 258 twin pairs had information regarding H. pylori status and history of peptic ulcer. Helicobacter pylori status was assessed as the presence of anti-H. pylori IgG.
  
  
  RESULTS
  The intraclass correlations for peptic ulcer disease for MZ twins reared apart and together and DZ twins reared apart and together were 0.67, 0.65, 0.22, and 0.35, respectively, which indicates that genetic effects are important for liability to peptic ulcer. The correlation coefficient for MZ twins reared apart (0.67) provides the best single estimate of the relative importance of genetic effects (heritability) for variation in liability to peptic ulcer disease, and structural model fitting analyses confirmed this result (heritability, 62%). The cross-twin cross-trait correlations for MZ and DZ twins were examined to determine whether genetic effects for peptic ulcer were shared with or independent of genetic influences for H. pylori. The cross-correlations for MZ and DZ twins were almost identical (0.25 and 0.29, respectively), suggesting that familial environmental rather than genetic influences mediate the association between peptic ulcer disease and H. pylori infection.
  
  
  CONCLUSIONS
  Genetic influences are of moderate importance for liability to peptic ulcer disease. Genetic influences for peptic ulcer are independent of genetic influences important for acquiring H. pylori infection.
authors.affiliation: Department of Medicine, Veterans Affairs Medical Center and Baylor College of Medicine, Houston, Texas 77030, USA. hmalaty@bcm.tmc.edu
authors.forename: H M
authors.initials: HM
authors.lastname: Malaty
authors.forename: D Y
authors.initials: DY
authors.lastname: Graham
authors.forename: I
authors.initials: I
authors.lastname: Isaksson
authors.forename: L
authors.initials: L
authors.lastname: Engstrand
authors.forename: N L
authors.initials: NL
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D016481:Helicobacter Infections / Q000150:complications* / Q000235:genetics*; D016480:Helicobacter pylori; D006801:Humans; D008297:Male; D008875:Middle Aged; D010437:Peptic Ulcer / Q000235:genetics* / Q000382:microbiology*; D012042:Registries; D013548:Sweden; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic