Life equations for the senescence process (1009.2)

Abstract

Gompertz law of mortality quantitatively describes the mortality rate of humans and almost all multicellular animals. However, this law was found empirically nearly 200 years ago and its underlying kinetic mechanism is still unclear. Research has shown that the mortality rate does not follow the Gompertz law at very advanced ages and the Gompertz law cannot explain why temperature can affect lifespan. The author proposed a reaction kinetic model with a time dependent rate coefficient to describe the survival and senescence processes. A new mortality rate equation is established. From this new mortality rate equation, we can obtain the Gompertz law of mortality and show that the Gompertz law is only true when age is less than a characteristic value of life, can derive some important equations reported in Nature (Shaw RF, et al. Temperature and life‐span in poikilothermous animals. Nature 196:454‐457, 1962) and Science (Strehler BL, et al. General theory of mortality and aging. Science 132(3418):14‐21, 1960), and can explain the important observation on mortality plateau at very advanced ages reported in Science (Carey JR, et al. Slowing of mortality rates at older ages in large medfly cohorts. Science 258(5081):457‐461, 1992). Equations derived from the new mortality rate equation can be used to estimate the limitation for average lifespan, the maximal longevity. The predicted results are consistent with human mortality and survival data and tendency. The derived equations can also explain experimental data regarding the effect of temperature on lifespan and predict the effect of body temperature on human lifespan. This study gives theoretical answers to questions such as: Why do we age? How long can we live? How can lifespan be extended?