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Longevity and Correlated Frailty in Multigenerational Families

¹ Huntsman Cancer Institute and ² Human Development and Family Studies, University of Utah, Salt Lake City.
³ Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Argentina.
⁴ Department of Oncological Sciences, University of Utah, Salt Lake City.

Address correspondence to Ken R. Smith, PhD, Human Development and Family Studies, 225 South 1400 East, University of Utah, Salt Lake City, Utah 84112. E-mail: ken.smith{at}fcs.utah.edu

Multigenerational pedigrees provide an opportunity for assessing the effects of unobserved environmental and genetic effects on longevity (i.e., frailty). This article applies Cox proportional hazards models to data from three-generation pedigrees in the Utah Population Database using two different frailty specification schemes that account for common environments (shared frailty) and genetic effects (correlated frailty). In a model that includes measures of familial history of longevity and both frailty effects, we find that the variance component due to genetic factors is comparable to the one attributable to shared environments: Standard deviations of the correlated and the shared frailty distributions are 0.143 and 0.186, respectively. Through simulations, we also show a greater reduction in the bias of parameter estimates for fixed covariates through the use of the correlated frailty model.