LINK BETWEEN AGING CLOCK AND MORTALITY RATE: RELIABILITY APPROACH





S. Doubal, P. Klemera

Charles University, Faculty of Pharmacy, Department of Biophysics, Heyrovskeho 1203, 500 05 Hradec Kralove, Czech Republic



The aim of this study is to analyze general properties of systems with aging controlled by pacemaker and an attempt to use the methodology of theory of reliability for interpretation of the results. The theory of reliability provides methodology of analysis of reliable function of complex systems. Its origin is connected with analysis of artificial systems in engineering but it is applied also in gerontology. The methodology enables (among others) create links between reliability characteristics of complex system (e.g. mortality rate) and reliability of subsystems and elements. In gerontology, the valuable information on reliability of organism may be derived from changes of mortality rate during aging. The rules which govern the behavior of mortality curves are as follows: 1) Mortality depends exponentially on age in human in the interval 35 – 85 years (Gompertz law). 2) The exponential character of growth of mortality is not influenced by changes of the structure of mortality. More generally: in available demographic data there are no indication of the influence of environment on exponential character of mortality. 3) Mortality curves corresponding to populations living in different environments have “convergent” character in Gompertz period of life (the higher is mortality in certain time, the lower is the following growth of mortality). 4) In advanced age, the growth of mortality is slowing down and seems to maintain constant level in very advanced age. These findings comply with pacemaker theories of aging. The theory of free radicals, mitochondrial theory of aging, endocrine theory of aging, some genetic theories of aging and others can be interpreted as cases of this category. The crucial problem is the identification of pacemaker(s) and quantification of links between pacemaker(s) and organisms as a whole. We have suggested a model of system with “Gompertzian” reliability controlled by pacemaker. Further we analyzed the behavior of pacemaker and discussed the problem of number of principal pacemakers. The conclusions are as follows: 1) There is probably only one principal pacemaker controlling the pace of aging in Gompertz period of life. 2) The pacemaker is not influenced by the state of organism. 3) The “pace” of pacemaker is the same during Gompertz period of life. 4) It seems natural and probable that the elements of pacemaker do not age, theirs failure rate is constant during the Gompertz period. 5) Aging begins before 35 years of life and continues without changes in character of principal causes until at least 85 years of life. 6) In advanced age (above 90 years) there are fundamental changes in the pace of aging. We believe that the hypotheses of mechanisms of aging must comply with Gompertz growth of mortality and related laws (points1-4) and may be inspired by reliability analysis. In other words, the proposed analysis may be used as a tool for verification of pacemaker theories of aging. Supported by grant of Czech Ministry of Education CEZ:J13/98:11600002




Key words: aging, pacemaker, mortality, reliability







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