Aging: damage accumulation versus increasing mortality rate.

If aging is understood as some process of damage accumulation, it does not necessarily lead to increasing mortality rate. Within the framework of a suggested generalization of the Strehler-Mildwan (1960) [B.L. Strehler, A.S. Mildvan (1960). General theory of mortality and aging, Science, 132, 14] model, we show that even for models with monotonically increasing degradation, the mortality rate can still decrease. The decline in vitality and functions, as manifestation of aging, is modeled by the monotonically decreasing quality of life function. Using this function, the initial lifetime random variable with ultimately decreasing mortality rate is 'weighted' to result in a new random variable, which is already characterized by the increasing mortality rate.