A return to time, cells, systems, and aging: V. Further thoughts on Gompertzian survival dynamics--the geriatric years.

In this paper, I attempt to address the problem of how to model the survival curve in the later lifespan years; the geriatric years. I present a new general model for a three group population in which the first group represents early life failure (neonatal failure), the second group represents the classical "Gompertzian failure", and the third group represents the later life failure or geriatric failure. Theoretical results are compared to the known biological data. It is demonstrated that this three group model embeds, within itself, a greater variety of the known biological survival dynamics. In particular, this new model resolves some of these issues concerning the failure of the pure Gompertzian to model the later life (geriatric) survival distribution.