The Quest for a General Theory of Aging and Longevity

Abstract

Extensive studies of phenomena related to aging have produced many diverse findings, which require a general theoretical framework to be organized into a comprehensive body of knowledge. As demonstrated by the success of evolutionary theories of aging, quite general theoretical considerations can be very useful when applied to research on aging. In this theoretical study, we attempt to gain insight into aging by applying a general theory of systems failure known as reliability theory. Considerations of this theory lead to the following conclusions: (i) Redundancy is a concept of crucial importance for understanding aging, particularly the systemic nature of aging. Systems that are redundant in numbers of irreplaceable elements deteriorate (that is, age) over time, even if they are built of elements that do not themselves age. (ii) An apparent aging rate or expression of aging is higher for systems that have higher levels of redundancy. (iii) Redundancy exhaustion over the life course explains a number of observations about mortality, including mortality convergence at later life (when death rates are becoming relatively similar at advanced ages for different populations of the same species) as well as late-life mortality deceleration, leveling off, and mortality plateaus. (iv) Living organisms apparently contain a high load of initial damage from the early stages of development, and therefore their life span and aging patterns may be sensitive to early-life conditions that determine this initial damage load. Thus, the reliability theory provides a parsimonious explanation for many important agingrelated phenomena and suggests a number of interesting testable predictions. We therefore suggest adding the reliability theory to the arsenal of methodological approaches applied to research on aging.

Delirium in medical inpatients: Adverse outcomes

“…Perhaps, this is why management strategies have gained limited ground thus far as they have been modelled on otherwise successful preventative strategies. Intervention strategies may indeed improve post-delirium outcomes 34 , but there remains no consensus 21,32 . We have proposed a number of hypotheses that provide possible mechanisms for continued adverse events in delirium.…”

“…The reliability theory of ageing states that the properties of failure mechanics also change at the limits of redundancy (when the system is on the brink of failure) 32 . At this point, the individual is no longer able to tolerate further deficits (Figure 1) with the insinuation that system collapse or death ensues.…”

Looking forward to a general theory on population aging

“…Frailty is a biologic syndrome of decreased physiological reserves and resistance to stressors causing vulnerability to adverse outcomes, independently of disability or comorbidity (88). The exhaustion of reserve, seen as redundancy, can explain late-life mortality deceleration (12,89). At these limits, frail persons cease to be able to resist environmental hazards or resist extremely weakly (90), which could explain the mortality plateaus observed today at age 110 and older (79).…”

“…These apparently contradictory trends in functioning and disability, which were at the origin of numerous and interesting health theories (5)(6)(7)(8)(9)(10), require a newer and wider conceptual framework, which will be first justified and then developed in the present article. The need of a general framework to organize the numerous findings related to aging has been recently underlined by others, but this was related more to mortality and longevity without great consideration for the population health status (11,12).…”

Telomeres and Reproductive Aging

“…Many theories have been proposed for aging, yet still, no single theory is able to account for all the different views. Among the most widely accepted theories on aging are the Hayflic limit theory and telomere theory (Gavrilov & Gavrilova, 2003). Shortened leukocyte telomere length is observed in individuals with aging-related diseases, including hypertension (Jeanclos et al, 2000;Benetos et al, 2001), insulin resistance Demissie et al, 2006;, atherosclerosis (Brouilette et al, 2003;Benetos et al, 2004), myocardial infarction (Brouilette et al, 2003(Brouilette et al, , 2007Cawthon et al, 2003), stroke (Fitzpatrick et al, 2007) and dementia Panossian et al, 2003).…”