Maximum life span

maximum reported age at death) is a measure of the maximum amount of time one or more members of a population have been observed to survive between birth and death. The term can also denote an estimate of the maximum amount of time that a member of a given species could survive between birth and dea

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In animal studies, maximum span is often taken to be the mean life span of the most long-lived 10% of a given cohort. By another definition, however, maximum life span corresponds to the age at which the oldest known member of a species or experimental group has died. Calculation of the maximum life span in the latter sense depends upon initial sample size.[1]

Maximum life span contrasts with mean life span (average life span, life expectancy), and longevity. Mean life span varies with susceptibility to disease, accident, suicide and homicide, whereas maximum life span is determined by "rate of aging".[2] Longevity refers only to the characteristics of the especially long lived members of a population, such as infirmities as they age or compression of morbidity, and not the specific life span of an individual.

The longest living person whose dates of birth and death were verified according to the modern norms of Guinness World Recordsand the Gerontology Research Group was Jeanne Calment (1875–1997), a Frenchwoman who reportedly lived to 122. Reduction of infant mortality has accounted for most of the increased average life span longevity, but since the 1960s mortality ratesamong those over 80 years have decreased by about 1.5% per year. "The progress being made in lengthening lifespans and postponing senescence is entirely due to medical and public-health efforts, rising standards of living, better education, healthier nutrition and more salubrious lifestyles."[3] Animal studies suggest that further lengthening of median human lifespan as well as maximum lifespan could be achieved through "calorie restriction mimetic" drugs or by directly reducing food consumption.[4] Although calorie restriction has not been proven to extend the maximum human life span, as of 2014, results in ongoing primate studies have demonstrated that the assumptions derived from rodents are valid in primates as well [Reference: Nature 1 April 2014].[5]

It has been proposed that no fixed theoretical limit to human longevity is apparent today.[6][7]Studies in the biodemography of human longevity indicate a late-life mortality deceleration law: that death rates level off at advanced ages to a late-life mortality plateau. That is, there is no fixed upper limit to human longevity, or fixed maximal human lifespan.[8]This law was first quantified in 1939, when researchers found that the one-year probability of death at advanced age asymptotically approaches a limit of 44% for women and 54% for men.[9]

However, this evidence depends on the existence of a late-life plateaus and deceleration that can be explained, in humans and other species, by the existence of very rare errors.[10][11] Age-coding error rates below 1 in 10,000 are sufficient to make artificial late-life plateaus, and errors below 1 in 100,000 can generate late-life mortality deceleration. These error rates cannot be ruled out by examining documents,[11] the standard because successful pension fraud, identity theft, forgeries and errors that leave no documentary evidence. This capacity for errors to explain late-life plateaus solves the "fundamental question in aging research is whether humans and other species possess an immutable life-span limit.",[12] indicating that humans do indeed have a lifespan limit.

Scientists have observed that a person's VO2max value (a measure of the volume of oxygen flow to the cardiac muscle) decreases as a function of age. Therefore, the maximum lifespan of a person could be determined by calculating when the person's VO2max value drops below the basal metabolic rate necessary to sustain life, which is approximately 3 ml per kg per minute.[13][page needed] On the basis of this hypothesis, athletes with a VO2max value between 50 and 60 at age 20 would be expected "to live for 100 to 125 years, provided they maintained their physical activity so that their rate of decline in VO2max remained constant".[14]

Longitudinal variations of physiological indices, such as complete blood counts(CBC), along individual aging trajectories revealed a linear increase of the organism state fluctuations range with age. The broadening could be explained by a progressive loss of physiological resilience measured by the individual blood factors inverse auto-correlation times. Extrapolation of this data suggested that organism state recovery time and variance would simultaneously diverge at a critical point of 120 – 150 years of age corresponding to a complete loss of resilience and hence should be incompatible with survival. The criticality resulting in the end of life is an intrinsic biological property of an organism that is independent of stress factors and signifies a fundamental or absolute limit of human lifespan [15].

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