title: A combined gamma frailty and normal random-effects model for repeated, overdispersed time-to-event data.
abstract: This paper presents, extends, and studies a model for repeated, overdispersed time-to-event outcomes, subject to censoring. Building upon work by Molenberghs, Verbeke, and Demétrio (2007) and Molenberghs et al. (2010), gamma and normal random effects are included in a Weibull model, to account for overdispersion and between-subject effects, respectively. Unlike these authors, censoring is allowed for, and two estimation methods are presented. The partial marginalization approach to full maximum likelihood of Molenberghs et al. (2010) is contrasted with pseudo-likelihood estimation. A limited simulation study is conducted to examine the relative merits of these estimation methods. The modeling framework is employed to analyze data on recurrent asthma attacks in children on the one hand and on survival in cancer patients on the other.
authors: I-BioStat, Universiteit Hasselt, Diepenbeek, Belgium I-BioStat, Katholieke Universiteit Leuven, Leuven, Belgium geert.molenberghs@uhasselt.be.
authors: Geert
authors: G
authors: Molenberghs
authors: I-BioStat, Universiteit Hasselt, Diepenbeek, Belgium I-BioStat, Katholieke Universiteit Leuven, Leuven, Belgium.
authors: Geert
authors: G
authors: Verbeke
authors: I-BioStat, Universiteit Hasselt, Diepenbeek, Belgium Study Program of Statistics, Universitas Brawijaya, Malang, Indonesia.
authors: Achmad
authors: A
authors: Efendi
authors: I-BioStat, Universiteit Hasselt, Diepenbeek, Belgium I-BioStat, Katholieke Universiteit Leuven, Leuven, Belgium.
authors: Roel
authors: R
authors: Braekers
authors: ESALQ, Piracicaba, São Paulo, Brazil.
authors: Clarice G B
authors: CG
authors: Demétrio
mesh_terms: D000328:Adult; D001249:Asthma / Q000503:physiopathology; D002675:Child, Preschool; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D015233:Models, Statistical; D009369:Neoplasms / Q000503:physiopathology; D012008:Recurrence
keywords: Weibull model; conjugacy; exponential model; frailty model; generalized Cauchy distribution; maximum likelihood; pseudo-likelihood; strong conjugacy