title: Gastroesophageal reflux disease in monozygotic and dizygotic twins.
abstract: OBJECTIVE
  Gastroesophageal reflux disease (GERD) interferes with the quality of life and carries an increased risk for esophageal adenocarcinoma. We investigated genetic influence in the development of reflux.
  
  
  METHODS
  We compared concordance for reflux in monozygotic (MZ) and dizygotic (DZ) twins. All twins age 55 and older in the nationwide Swedish Twin Registry were invited to participate. Data were collected by computer-assisted telephone interviews. Reflux disease was defined by symptomatic heartburn or acid regurgitation occurring at least weekly.
  
  
  RESULTS
  A total of 2178 monozygotic, 3219 same-sex dizygotic, and 3014 unlike-sex dizygotic twin pairs provided information. Overall, 15.3% of the twins had reflux. In men, the intraclass correlation for reflux was 0.29 (95% confidence interval [CI], 0.15-0.43) for monozygotic and 0.13 (95% CI, 0.02-0.25) for dizygotic pairs. In women, the correlation was 0.33 (95% CI, 0.22-0.44) for monozygotic and 0.14 (95% CI, 0.04-0.24) for dizygotic pairs. For unlike-sex dizygotic pairs, the correlation was 0.06 (95% CI, -0.01 to 0.14). Concordance for reflux was not caused by inherited obesity or alcohol use; inherited smoking may be a minor factor.
  
  
  CONCLUSIONS
  The increased concordance for reflux in monozygotic pairs, compared with dizygotic pairs, indicates genetic rather than shared environmental effects. Heritability accounted for 31% (23%-39%) of the liability to reflux disease in this population.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota 55905, USA. cameron.alan@mayo.edu
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Cameron
authors.forename: Jesper
authors.initials: J
authors.lastname: Lagergren
authors.forename: Christer
authors.initials: C
authors.lastname: Henriksson
authors.forename: Olof
authors.initials: O
authors.lastname: Nyren
authors.forename: G Richard
authors.initials: GR
authors.lastname: Locke
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Pedersen
mesh_terms: D000368:Aged; D004200:Diseases in Twins / Q000453:epidemiology*; D005260:Female; D005764:Gastroesophageal Reflux / Q000453:epidemiology* / Q000235:genetics; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D017678:Sex Distribution; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic / Q000706:statistics & numerical data*; D014430:Twins, Monozygotic / Q000706:statistics & numerical data*