Case-cohort sampling is a commonly used and efficient method for studying large cohorts.In many situations,some covariates are easily measured on all cohort subjects,and surrogate measurements of the expensive covariates also may be observed.In this paper,to make full use of the covariate data collected outside the case-cohort sample,we propose a class of weighted estimators with general time-varying weights for the additive hazards model,and the estimators are shown to be consistent and asymptotically normal.We also identify the estimator within this class that maximizes efficiency,and simulation studies show that the efficiency gains of the proposed estimator over the existing ones can be substantial in practical situations.A real example is provided.
Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparametric mixed effect model with time-varying latent effects in the analysis of longitudinal data with informative observation times and a dependent terminal event. Estimating equation approaches are developed for parameter estimation, and asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.
Longitudinal data often arise when subjects are followed over a period of time,and in many situations,there may exist informative observation times and a dependent terminal event such as death that stops the follow-up.In this article,we propose joint modeling and analysis of longitudinal data with possibly informative observation times and a dependent terminal event in which a common subject-specific latent variable is used to characterize the correlations.A borrow-strength estimation procedure is developed for parameter estimation,and both large-sample and finite-sample properties of the proposed estimators are established.In addition,some goodness-of-fit methods for assessing the adequacy of the model are provided.An application to a bladder cancer study is illustrated.
Multivariate recurrent event data arises when study subjects may experience more than one type of recurrent events. In some situations, however, although event times are always observed, event categories may be partially missing. In this paper, an additive-multiplicative rates model is proposed for the analysis of multivariate recurrent event data when event categories are missing at random. A weighted estimating equations approach is developed for parameter estimation, and the resulting estimators are shown to be consistent and asymptotically normal. In addition, a model-checking technique is presented to assess the adequacy of the model. Simulation studies are conducted to evaluate the finite sample behavior of the proposed estimators, and an application to a platelet transfusion reaction study is provided.
Panel count data occur in many clinical and observational studies and in some situations the observation process is informative.In this article,we propose a new joint model for the analysis of panel count data with time-dependent covariates and possibly in the presence of informative observation process via two latent variables.For the inference on the proposed model,a class of estimating equations is developed and the resulting estimators are shown to be consistent and asymptotically normal.In addition,a lack-of-fit test is provided for assessing the adequacy of the model.The finite-sample behavior of the proposed methods is examined through Monte Carlo simulation studies which suggest that the proposed approach works well for practical situations.Also an illustrative example is provided.
