Genetic studies are continuing to generate volumes and variety of data that can be used to examine the genetic effects. Often the effect of a genetic variant varies by nongenetic measures, what is traditionally defined as gene-environment interaction (G×E). If the G×E term is neglected, estimates of the main effects can be substantially biased. We derive a general and convenient approximation to the magnitude of bias in the estimates due to omitting the G×E term. We show that the approximation is reasonably accurate in finite samples. We then apply the approximation in a study of Alzheimer's disease.
Keywords: Alzheimer’s disease; Kullback-Leibler divergence; case-control studies; gene-environment interactions (G×E); omitting variables.
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