Gerontology lost in translation from demography to biology of aging and back.

Changes in human survival and mortality patterns resulting in life expectancy (LE) increase are profoundly significant for society and critically depend on societal factors but cannot escape frames defined by biology. Demography, a social discipline, uses descriptive terms, such as survival curve rectangularization, mortality compression, lifespan disparity reduction, and mean (modal, median) lifespan increase, to define the beneficial changes thought possible due to deceleration of aging. The reasonability of this objective is questioned in the present article based on the premises that changes in mortality correlate linearly with changes in the pressure of causes of death and exponentially with changes in the ability to resist them. The biological background of these premises is essentially Gompertz-Makeham law (GML) generalization, which accommodates the possibility that the rate of aging and the pressure of causes of death may not be constant during lifespan. This topic is discussed with account for the compensation effect of mortality (CEM): viability correlates positively with the rate of its aging-associated declines. It is concluded that (i) aging deceleration is incompatible with beneficial demographic changes if the GML and CEM are valid; (ii) reducing the pressure of the extrinsic modifiable causes of death in countries featuring the highest LE cannot increase it by more than five years, and (iii) possible increases in LE are negatively correlated with its current levels.