title: A copula model for repeated measurements with non-ignorable non-monotone missing outcome.
abstract: A normal copula-based selection model is proposed for continuous longitudinal data with a non-ignorable non-monotone missing-data process. The normal copula is used to combine the distribution of the outcome of interest and that of the missing-data indicators given the covariates. Parameters in the model are estimated by a pseudo-likelihood method. We first use the GEE with a logistic link to estimate the parameters associated with the marginal distribution of the missing-data indicator given the covariates, assuming that covariates are always observed. Then we estimate other parameters by inserting the estimates from the first step into the full likelihood function. A simulation study is conducted to assess the robustness of the assumed model under different missing-data processes. The proposed method is then applied to one example from a community cohort study to demonstrate its capability to reduce bias.
authors.affiliation: Division of Biostatistics, School of Medicine, Indiana University, 1050 Wishard Boulevard RG R4101, Indianapolis, IN 46202, USA. chashen@iupui.edu
authors.forename: Changyu
authors.initials: C
authors.lastname: Shen
authors.forename: Lisa
authors.initials: L
authors.lastname: Weissfeld
mesh_terms: D000368:Aged; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D003704:Dementia / Q000453:epidemiology; D006801:Humans; D016013:Likelihood Functions; D008137:Longitudinal Studies; D015233:Models, Statistical