Faculté des sciences et de médecine

Aging and Its Demographic Measurement

Bronikowski, Anne M. ; Flatt, Thomas

In: Nature Education Knowledge, 2010, vol. 1, no. 12, p. 1-6

This case study highlights the general issues raised earlier. First, that maximum lifespan is not an easily obtainable metric. Specifically, it is unambiguous in the sense that once the last animal dies, it is most definitely dead. But to estimate the variance in maximum lifespan, many replicate populations would need to be followed for each treatment group (with each replicate providing a single... More

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    Summary
    This case study highlights the general issues raised earlier. First, that maximum lifespan is not an easily obtainable metric. Specifically, it is unambiguous in the sense that once the last animal dies, it is most definitely dead. But to estimate the variance in maximum lifespan, many replicate populations would need to be followed for each treatment group (with each replicate providing a single observation of maximum lifespan). Second, median lifespan, although measurable from a single population, provides no information on the age-specificity and patterns in age-specific vital rates that are contributing to differences in "aging" (i.e., differences in physiological frailty and rates of increasing mortality across the adult lifespan). Finally, our partitioning of aging into two components — IMR and RoA — allows us to unravel causation in a demographic sense. Specifically, it allows us to specify an aging rate that is separate from its starting value (IMR), independent of fluctuations in survival due to temporary experimental impacts, and not necessarily equivalent to expectations due to median or maximum lifespan.