Search for an unitary mortality law through a theoretical model for biological ageing (original) (raw)
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A model of aging and a shape of the observed force of mortality
Lifetime data analysis, 2003
A probabilistic model of aging is considered. It is based on the assumption that a random resource, a stochastic process of aging (wear) and the corresponding anti-aging process are embedded at birth. A death occurs when the accumulated wear exceeds the initial random resource. It is assumed that the anti-aging process decreases wear in each increment. The impact of environment (lifestyle) is also taken into account. The corresponding relations for the observed and the conditional hazard rate (force of mortality) are obtained. Similar to some demographic models, the deceleration of mortality phenomenon is explained via the concept of frailty. Simple examples are considered.
A bit-string model for biological aging
Journal of Statistical Physics, 1995
We present a simple model for biological aging. We studied it through computer simulations and we have found this model to reflect some features of real populations.
Exact Results of the Bit-String Model for Catastrophic Senescence
Journal de Physique I, 1995
We succeeded in obtaining exact results of the bit-string model of biological aging for populations whose individuals breed only once. These results are in excellent agreement with those obtained through computer simulations. In addition, we obtain an expression for the minimum birth needed to avoid mutational meltdown.
A New Model of Ageing and Mortality
British Actuarial Journal, 2009
The Nested Binomial Model presented in this paper is a new approach to modelling mortality and survival in humans and other species that seeks to reconcile individual life course risk trajectories and those population mortality patterns that arise from inter-individual heterogeneity. In describing individual trajectories it partitions mortality risk into two main elements: 'redundancy' and 'interactive risk'. Interactive risk is volatile, increasing or decreasing with time and circumstance, while redundancy is a quantity which declines in a linear and largely invariable fashion throughout life. Although a biological correlate for redundancy is not identified, this assumption allows strikingly realistic modelling of mortality and survival curves, late-life mortality deceleration, Strehler-Mildvan correlation, mortality plateaux and slowing of mortality. Simple assumptions with regard to heterogeneity of parameters within the model allow close approximation to the entire human mortality curve, and provide a rationale for observed and otherwise paradoxical population mortality phenomena. As such, it fulfils biodemographic criteria for a comprehensive theory of ageing. Future challenges are to reconcile its theoretical structure with empirical findings in the biology of ageing and to render it in a form that can become a usable actuarial tool. keywords Mortality Laws; Survival Models; Gompertz; Makeham; Biological Models
Theoretical approach to biological aging
Physica A: Statistical Mechanics and its Applications, 1998
We present a model for biological aging that considers the number of individuals whose (inherited) genetic charge determines the maximum age for death: each individual may die before that age due to some external factor, but never after that limit. The genetic charge of the offspring is inherited from the parent with some mutations, described by a transition matrix. The model can describe different strategies of reproduction and it is exactly soluble. We applied our method to the bit-string model for aging and the results are in perfect agreement with numerical simulations.
Experimental Gerontology, 2001
Main problems of modeling the link between aging processes and mechanisms of mortality are addressed. Various applications of Gompertz's law, which allowed to formulate some fruitful hypotheses on the ®eld, are reviewed. Some pitfalls occurring in its applications are also discussed using a model built on purpose to overcome these dif®culties. The role played by heterogeneity emerges as the common cause of some relevant failure in using Gompertz's law and the necessary key ingredient of any model aimed to interpret the link between aging and mortality correctly. Though a number of problems are related to inter-individual variability, the search for their solution can lead to an intriguing approach to the study of aging and mortality. Living beings can be considered as complex systems and their age-related changes can be described at the light of complex system theory.
Mechanics of population aging and survival
Biogerontology, 2018
In this paper we extend the previous work of Witten and her team on defining a classical physicsdriven model of survival in aging populations (Eakin,
A Model of Aging and a Shape of the Observed Hazard Rate
2002
A probabilistic model of biological aging is considered. It is based on the assumption that a random resource, a stochastic process of aging (wear) and the corresponding anti-aging process are embedded at birth. A death occurs when the accumulated wear exceeds the initial random resource. It is assumed that the anti-aging process decreases wear in each increment. The impact of environment (lifestyle) is also taken into account. The corresponding relations for the observed and the conditional hazard rate are obtained. Similar to some demographic models, the deceleration of mortality phenomenon is explained via the concept of frailty.
Expectation of life at old age predicted from a single death rate: Models and applications
2017
This paper introduces empirical relations between the death rate at a given age and the remaining life expectancy at that same age. The relations prove to be of prediction accuracy exceeding that of the common alternative, extrapolation of the death rates into older ages based on data at younger ages. Being close in accuracy to models by Horiuchi, Coale and Mitra, the proposed models may be of use in cases when the latter models may not be applied because of either lack of data on old-age mortality or violation of the underlying assumptions, such as population stability. Combining the proposed models with constrained extrapolations of old-age mortality will be a useful tool in estimating and projecting old-age mortality, completing life tables for young cohorts and extending model and empirical life tables to old age.