Biostatistics Advance Access originally published online on March 18, 2009
Biostatistics 2009 10(3):451-467; doi:10.1093/biostatistics/kxp004
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Conditional GEE for recurrent event gap times
Department of Statistical Science, Cornell University, Ithaca, NY 14853-7801, USA
dyc24{at}cornell.edu
Department of Biological Statistics and Computational Biology and Department of Statistical Science, Cornell University, Ithaca, NY 14853-7801, USA
rls54{at}cornell.edu
* To whom correspondence should be addressed.
This paper deals with the analysis of recurrent event data subject to censored observation. Using a suitable adaptation of generalized estimating equations for longitudinal data, we propose a straightforward methodology for estimating the parameters indexing the conditional means and variances of the process interevent (i.e. gap) times. The proposed methodology permits the use of both time-fixed and time-varying covariates, as well as transformations of the gap times, creating a flexible and useful class of methods for analyzing gap-time data. Censoring is dealt with by imposing a parametric assumption on the censored gap times, and extensive simulation results demonstrate the relative robustness of parameter estimates even when this parametric assumption is incorrect. A suitable large-sample theory is developed. Finally, we use our methods to analyze data from a randomized trial of asthma prevention in young children.
Keywords: Asthma; Censoring; Generalized estimating equation; Intensity model; Longitudinal data; Marginal model
Received February 21, 2008; revised October 16, 2008; accepted for publication November 18, 2008.