Frailty models are used in survival analysis to model unobserved heterogeneity. To study such heterogeneity by the inclusion of a random term called the frailty is assumed to multiply hazards of all subjects in the shared frailty. We study compound negative binomial distribution as frailty distribution and two different baseline distributions namely Pareto and linear failure rate distribution i...

OBJECTIVES Neglecting the presence of unobserved heterogeneity in survival analysis models has been showed to potentially lead to underestimating the effect of the covariates included in the analysis. This study aimed to investigate the role of unobserved heterogeneity of frailty on the estimation of mortality differentials from age 50 on by education level. DESIGN Longitudinal mortality foll...

BACKGROUND Frailty in the elderly can be regarded as nonspecific vulnerability to adverse health outcomes, caused by multiple factors. The aim was to analyze the relationships between the frailty index, age and mortality in a two year follow up study of Mexican elderly. METHODS A frailty index was developed using 34 variables. To obtain the index, the mean of the total score for each individu...