A DUALITY IN AGING - THE EQUIVALENCE OF MORTALITY MODELS BASED ON RADICALLY DIFFERENT CONCEPTS

Several alternative mortality models fit Swedish old-age mortality dat a equally well. The models build on two different concepts of the hete rogeneity of individuals in a population. The first concept concerns f ixed, genetic differences among individuals in their risk of death. Th e second concept involves acquired susceptibility to death due to phys iological changes and environmental influences. We show that alternati ve mortality models based on either of these two concepts or some mix of them lead to the same parametric form of observed age-specific deat h rates. We discuss this duality property of mortality processes and s how that even when a mortality model fits the data, the concepts used to construct the model may not be correct.