Comparing the Relative Efficacy of Generalized Estimating Equations, Latent Growth Curve Modeling, and Area Under the Curve with a Repeated Measures Discrete Ordinal Outcome Variable

Researchers are often interested in how changes in one variable influence changes in a second variable, requiring the repeated measures of two variables. There are several multivariate statistical methods appropriate for this research design, including generalized estimating equations (GEE) and latent growth curve modeling (LGCM). Both methods allow for variables that are not continuous in measurement level and not normally distributed. More recently, researchers have begun to employ area under the curve (AUC) as a potential alternative when the nature of change is less important than the overall effect of time on repeated measures of a random variable. The research showed that AUC is an acceptable alternative to LGCM with repeated measures of a continuous and a zero-inflated Poisson random variable. However, less is known about its performance relative to GEE and LGCM when the repeated measures are ordinal random variables. Further, to our knowledge, no study has compared AUC to LGCM or GEE when there are two longitudinal processes. We thus compared AUC to LGCM and GEE, assessing the effects of repeated measures of psychological distress on repeated measures of smoking. Results suggest AUC performed equally well with both methods, although missing data management is an issue with both AUC and GEE.