Demographic window to aging in the wild: constructing life tables and estimating survival functions from marked individuals of unknown age

Abstract

SummaryWe address the problem of establishing a survival schedule for wild populations. A demographic key identity is established, leading to a method whereby age-specific survival and mortality can be deduced from a marked cohort life table established for individuals that are randomly sampled at unknown age and marked, with subsequent recording of time-to-death. This identity permits the construction of life tables from data where the birth date of subjects is unknown. An analogous key identity is established for the continuous case in which the survival schedule of the wild population is related to the density of the survival distribution in the marked cohort. These identities are explored for both life tables and continuous lifetime data. For the continuous case, they are implemented with statistical methods using non-parametric density estimation methods to obtain flexible estimates for the unknown survival distribution of the wild population. The analytical model provided here serves as a starting point to develop more complex models for residual demography, i.e. models for estimating survival of wild populations in which age-at-entry is unknown and using remaining information in randomly encountered individuals. This is a first step towards a broad new concept of 'expressed demographic information content of marked or captured individuals'.

Red cell life span heterogeneity in hematologically normal people is sufficient to alter HbA1c

“…Even though age cohort survival is not measured, the RBC age distribution at the time of labeling and any subsequent time can be derived from the survival curve of labeled RBCs 27 by adapting a method used to compute mean age of wild animals in catch-and-release studies. 29,30 Of importance for the studies described here and in contrast to the 51 Cr method, biotin-labeled RBCs can be recovered from the circulation for analysis of HbA1c.…”

“…RBC survival was determined from the disappearance of biotin-labeled cells and expressed as mean age of the RBC population at the time of labeling. 29,30 Methods Study subjects DM subjects (both type 1 and 2) were selected to represent a range of discordance between HbA1c and serum FA. 36 Inclusion criteria were: age more than or equal to 14 years, either gender, and diabetes maintained at stable level of control.…”

Symmetries between life lived and left in finite stationary populations

“…Following Rao and Carey's idea, our inspiration also comes from an empirical set-up in which capture ages are unknown, but individuals are followed until death, which is a common scenario in many studies on wild animals (Müller et al 2004(Müller et al , 2007. However, it also applies to human populations when the ages of individuals are unknown, as may be the case in historical data or other kinds of incomplete demographic data.…”

“…One of the main results that has recently emerged is "Carey's equality," as first coined by Vaupel (2009), which establishes that the age composition equals the distribution of remaining lifetimes in stationary populations. To our knowledge, this relationship was first described by Brouard (1989), and was later and independently noticed by James Carey in the study of the survival patterns of captive and follow-up cohorts of med-flies (Müller et al 2004(Müller et al , 2007. Hence, we choose to refer to this relationship as the 'Brouard-Carey equality.'…”

“…Examples are found in the fields of demography and population biology (Goldstein 2009(Goldstein , 2012Kim and Aron 1989;Müller et al 2004Müller et al , 2007Riffe 2015;Vaupel 2009), and reliability engineering (Cha and Finkelstein 2016;Finkelstein and Vaupel 2015). One of the main results that has recently emerged is "Carey's equality," as first coined by Vaupel (2009), which establishes that the age composition equals the distribution of remaining lifetimes in stationary populations.…”