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.