Decline in telomere length with increasing age across non‐human vertebrates: a meta‐analysis

The prediction that telomere length (TL) shortens with increasing age is a
major element in considering the role of telomeres as a key player in
evolution. While telomere attrition is found in humans both in vitro and
in vivo, the increasing number of studies reporting diverse age-specific
patterns of TL challenges the hypothesis of a universal decline of TL with
increasing age. Here we performed a meta-analysis to estimate the
relationship between TL and age across 175 estimates encompassing 98
species of vertebrates. We found that, on average, TL does decline with
increasing age during adulthood. However, this decline was weak and
variable across vertebrate classes, and we also found evidence for a
publication bias that might weaken our current evidence of decreasing TL
with increasing age. We found no evidence for a faster decline in TL with
increasing age when considering the juvenile stage (from birth to age at
first reproduction) compared to the adult stage. Heterogeneity in TL
ageing rates was explained by the method used to measure telomeres:
detectable TL declines with increasing age were found only among studies
using TRF with in-gel hybridisation and qFISH methods, but not in studies
using qPCR and Southern blot-based TRF methods. While we confirmed that TL
declines with increasing age in most adult vertebrates, our results
identify an influence of telomere measurement methodology, which
highlights the need to examine more thoroughly the effect of the method of
measurement on TL estimates.