Estimating and comparing univariate associations with application to the prediction of adult obesity

Studies examining the association between an outcome variable and multiple predictors are common in medical research. Examples include epidemiologic studies of risk factors for disease and clinical studies of prognostic indicators for diseased subjects. This paper is concerned with the assessment of the associations between the outcome and each predictor separately, the so-called univariate associations. Comparisons between predictors in regards to the strengths of their association with the outcome are considered. We show that though such comparisons cannot be made with standard techniques, they can be made using an algorithm which performs all of the univariate analyses simultaneously. This is accomplished with a non-standard application of generalized estimating equation methods. Comparisons of univariate associations are shown to be the key analyses of interest in a retrospective longitudinal study of childhood predictors of adult obesity. We illustrate the methodology on data from this study.