et al. [2009] used a two-level factor analysis for longitudinal data. Maenner et al. and Gu et al. used a generalized estimating equations model to confirm the results from their primary analysis while accounting for familial correlation. The use of longitudinal data in studies of G×E interactions is particularly appealing because it may help overcome some of the pitfalls discussed above. Specifically, some of the power lost by conducting a G×E analysis using GWA data may be recaptured by the use of longitudinal data and having multiple measurements of the environmental exposure may lessen the problem of measurement error.
