title: Cigarette smoking increases the risk of rheumatoid arthritis. Results from a nationwide study of disease-discordant twins.
abstract: OBJECTIVE
  To test the hypothesis that cigarette smoking is associated with susceptibility to rheumatoid arthritis (RA) by comparing smoking history between twins with RA and their unaffected co-twins.
  
  
  METHODS
  Interview questionnaires on smoking history were administered to 79 identical (monozygotic [MZ]) and 71 same-sex nonidentical (dizygotic, [DZ]) twin pairs who were discordant for RA, recruited from the Arthritis and Rheumatism Council Twin Study. Results were expressed as odds ratios (OR) with 95% confidence intervals (95% CI).
  
  
  RESULTS
  Although most twin pairs were concordant for smoking history, there was a strong association between ever smoking and RA in the MZ pairs (OR 12.0, 95% CI 1.78-513), with a similar trend observed in the DZ pairs (OR 2.5, 95% CI 0.92-7.87).
  
  
  CONCLUSIONS
  The discordance in cigarette smoking history for individuals who are at presumed identical genetic risk for RA supports other data suggesting the role of smoking in disease susceptibility.
authors.affiliation: University of Manchester, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: Silman
authors.forename: J
authors.initials: J
authors.lastname: Newman
authors.forename: A J
authors.initials: AJ
authors.lastname: MacGregor
mesh_terms: D001172:Arthritis, Rheumatoid / Q000209:etiology*; D004198:Disease Susceptibility; D004200:Diseases in Twins / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic