Modelling the survival function of the Spanish population by the Wong–Tsui model with the incorporation of frailty and covariates

This paper presents a variant of the survival function proposed by Wong and Tsui, in which we include a component reflecting heterogeneity among individuals (frailty), together with a covariate describing the influence of certain characteristics of individuals on the response variable. Using mortality statistics for the entire Spanish population, we estimated survival functions according to the variants of the model considered, also determining life expectancies and mortality ratios at each age. The advantage of the proposed variant is that it incorporates gender differences, by including sex as a covariate. Furthermore, it reflects the intrinsic randomness of individuals. With this approach, additional parameters must be considered, but all were found to be significant.