DOI: 10.1093/aje/kwg147 Selection Bias in the Assessment of Gene-Environment Interaction in Case-Control Studies

Selection bias is a common concern in epidemiologic studies, particularly case-control studies. Selection bias in the odds ratio occurs when participation depends jointly on exposure and disease status. General results for understanding when selection bias may affect studies involving gene-environment interactions have not yet been developed. In this paper, the authors show that the assessment of gene-environment interactions will not be subject to selection bias under the assumption that genotype does not influence participation conditional on exposure and disease status. This is true even when selection, including self-selection of subjects, is jointly influenced by exposure and disease and regardless of whether the genotype is related to exposure, disease, or both. The authors present an example to illustrate this concept. bias (epidemiology); case-control studies; environment; epidemiologic methods; genotype; polymorphism (genetics); risk factors; selection bias In the search for causative agents of human diseases, both environmental and genetic risk factors have been identified. The relative influence of the two is highly variable, yet for most diseases, it is unlikely that purely environmental or purely genetic etiologies will sufficiently explain th