Telomere length and chronological age across the human lifespan: A systematic review and meta-analysis of 414 study samples including 743,019 individuals

Telomere length is not a useful tool for chronological age estimation in animals

“…[49,50] Curiously, Le Clercq et al [1] suggested that telomeres do not shorten in somatic cells in juveniles, but there is no evidence for their general claim that "telomere length remains stable in most tissues throughout childhood from infancy to early adulthood." In humans, a rapid decline in TL is observed in infants, [51][52][53][54] which is similar to results from, for example, baboons (Papio hamadryas [55] ), Soay sheep (Ovis aries [56] ) and some bird species. [48,57] For TL to remain stable during this period of rapid growth, would require the expression of telomerase or some other mechanism of telomere maintenance to be active in somatic cells, which is generally thought not to be the case in humans and several other mammals.…”

“…[45] Some small mammal species and long-lived seabirds may express telomerase and lengthen or maintain telomeres through life. [58,59] Thus, TL occasionally lengthen with age in some species, but generally shorten with age both in young and old individuals or in a non-linear manner, [17,47,54] and it is apparently not possible to outline a simple TL change trajectory that is universal across any vertebrate class.…”

Early origins of health and disease risk: The case for investigating adverse exposures and biological aging in utero, across childhood, and into adolescence

“…The timing and pace of developmental processes, as well as the stability and resilience of the physiological systems developed early in life (e.g., inflammatory immune responses, glucose metabolism, and epigenetic regulation), play key roles in constraining an individual's lifelong aging trajectory (Feltes et al., 2014; Lui et al., 2010). Biological aging occurs throughout life but is generally most rapid in the early stages, particularly during embryonic development and childhood (Cowell et al., 2021; Snir et al., 2019; Ye et al., 2023). These periods are characterized by a high rate of growth and development, which is captured by biological aging measures as an increased rate of aging and an older biological age.…”

“…Theory and empirical evidence indicate that children's telomeres are plastic during development, receptive to the influence of early life conditions, and particularly vulnerable to environmental insults (Entringer et al., 2012; Shalev, 2012). TL shortening occurs naturally throughout life (Ye et al., 2023), but TL erodes most rapidly in the first years of life as a result of intense somatic growth (Zeichner et al., 1999) and rapid expansion of progenitor cells in the hematopoietic hierarchy (Sidorov et al., 2009; Werner et al., 2015), reflecting a sensitive period of development wherein adverse environmental exposures may be especially detrimental. Studies have shown that early life stress can lead to shorter telomeres in children (Coimbra et al., 2017), predisposing them to earlier onset health problems.…”

“…Also, TL features considerable interindividual variability, with some individuals naturally having shorter telomeres without any apparent health implications (Monaghan & Haussmann, 2006). Finally, certain methodological factors, such as methods of DNA extraction and quantification, tissue types, or the use of diverse assays to measure TL (e.g., qPCR, Southern blot), can influence measured TL, complicating its interpretation across studies as a straightforward marker of biological age (Nettle et al., 2021; Wolf & Shalev, 2023; Ye et al., 2023).…”