title: Detection of gene-environment interaction by case-only studies.
abstract: BACKGROUND
  The detection of gene-environment interaction can provide important clues not only for resolving biological mechanisms underlying diseases, but also for disease prevention. The newly introduced case-only study was compared with traditional case-control study in terms of statistical power to detect significant gene-environment interaction.
  
  
  METHODS
  Odds ratios for interaction were calculated in the framework of case-control study and case-only study separately, by an unconditional logistic model. Hypothetical data with 200 cases and 200 or 400 controls and real published data derived from four cancer case-control studies of genotype and smoking were used for the comparisons.
  
  
  RESULTS
  Although odds ratio estimates for interaction were the same, 95% confidence intervals were narrower in case-only studies than in case-control studies. Similarly, there were no substantial differences in point estimates for interaction in four real cancer case-control studies between the two study designs, but the confidence intervals were narrower with the case-only study.
  
  
  CONCLUSIONS
  Although the case-only study does not provide odds ratios for exposure or genotype alone, it is very useful for the detection of interaction, especially for screening purposes.
authors.affiliation: Division of Epidemiology, Aichi Cancer Center Research Institute, Nagoya, Japan. nhamajim@aichi-cc.pref.aichi.jp
authors.forename: N
authors.initials: N
authors.lastname: Hamajima
authors.forename: H
authors.initials: H
authors.lastname: Yuasa
authors.forename: K
authors.initials: K
authors.lastname: Matsuo
authors.forename: Y
authors.initials: Y
authors.lastname: Kurobe
mesh_terms: D016022:Case-Control Studies; D004777:Environment; D004812:Epidemiologic Methods; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D008433:Mathematics; D009369:Neoplasms / Q000235:genetics*; D016017:Odds Ratio; D011110:Polymorphism, Genetic; D012107:Research Design / Q000592:standards*; D012907:Smoking