Multivariate survival data under bivariate frailty: An estimating equationapproach

A modified frailty model is developed to improve the computing efficiency o f the bivariate frailty model proposed by Xue and Brookmeyer (1996, Lifetim e Data Analysis 2, 277-290) for the analysis of multivariate survival data. Originally, the frailty was modeled parametrically and a modified EM appro ach was used to estimate the parameters of interest, however, with intensiv e computations. The modified frailty model formulates a Poisson regression model and applies quasi-likelihood estimating equations to estimate the par ameters of interest. This procedure not only significantly reduces the comp utation but also avoids using a parametric assumption for the frailty distr ibution. Simulation studies show the estimators perform well. The method is also applied to a mental health care dataset.