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Coefficient of Variation of Lifespan Across the Tree of Life: Is It a Signature of Programmed Aging?

G. A. Shilovsky1,2*, T. S. Putyatina2, V. V. Ashapkin1, O. S. Luchkina3, and A. V. Markov2

1Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; E-mail: gregory_sh@list.ru, gr_gerontol@gmail.com

2Lomonosov Moscow State University, Faculty of Biology, 119991 Moscow, Russia

3Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, 119071 Moscow, Russia

* To whom correspondence should be addressed.

Received August 9, 2017; Revision received September 15, 2017
Measurements of variation are of great importance for studying the stability of pathological phenomena and processes. For the biology of aging, it is very important not only to determine average mortality, but also to study its stability in time and the size of fluctuations that are indicated by the variation coefficient of lifespan (CVLS). It is believed that a relatively small (~20%) value of CVLS in humans, comparable to the coefficients of variation of other events programmed in ontogenesis (for example, menarche and menopause), indicates a relatively rigid determinism (N. S. Gavrilova et al. (2012) Biochemistry (Moscow), 77, 754-760). To assess the prevalence of this phenomenon, we studied the magnitude of CVLS, as well as the coefficients of skewness and kurtosis in diverse representatives of the animal kingdom using data provided by the Institute for Demographic Research (O. R. Jones et al. (2014) Nature, 505, 169-173). We found that, unlike humans and laboratory animals, in most examined species the values of CVLS are rather high, indicating heterogeneity of the lifespan in the cohorts studied. This is probably due to the large influence of background mortality, as well as the non-monotonicity of total mortality in the wild, especially at the earliest ages. One way to account for this influence is to “truncate” the data (removing the earliest and latest ages from consideration). To reveal the effect of this procedure, we proposed a new indicator, the stability coefficient of mortality dynamics, which indicates how quickly CVLS is reduced to values that characterize a relatively homogeneous population (33%) when the data are “truncated”. Such indicators facilitate the use of the parameters of survival curves for analysis of the effects of geroprotectors, lifestyle, and other factors on lifespan, and for the quantification of relative contributions of genetic and environmental factors to the dynamics of aging in human and animal populations, including those living in the wild.
KEY WORDS: aging, lifespan, mortality rate, survival curves, skewness, coefficient of variation

DOI: 10.1134/S0006297917120070