Adult Telomere Length Research Articles

Noisy nests: Early-life noise exposure impacts songbird fitness.

Recent findings indicate that noise pollution - presented in the absence of other variables - has both immediate-term impacts on young birds' developmental rates and physiology as well as long-term effects on adult telomere length and reproductive success. This work highlights yet another set of negative impacts caused by anthropogenic noise, and suggests that the dramatic fitness consequences observed likely have implications for the evolution of learning and behavior in animals living in noisy environments.

Association Between Adverse Early Life Factors and Telomere Length in Middle and Late Life.

Telomere length (TL) has been acknowledged as biomarker of biological aging. Numerous investigations have examined associations between individual early life factors and leukocyte TL; however, the findings were far from consistent. We evaluated the relationship between individual and combined early life factors and leukocytes TL in middle and late life using data from the UK Biobank. The early life factors (eg, maternal smoking, breastfeeding, birth weight, and comparative body size and height to peers at age 10) were measured. The regression coefficients (β) and 95% confidence interval (CI) were applied to assess the link of the early life factors and TL in adulthood. Flexible parametric survival models incorporated age to calculate the relationship between early life factors and life expectancy. Exposure to maternal smoking, lack of breastfeeding, low birth weight, and shorter height compared to peers at age 10 were identified to be associated with shorter TL in middle and older age according to the large population-based study with 197 504 participants. Individuals who experienced more than 3 adverse early life factors had the shortest TL in middle and late life (β = -0.053; 95% CI = -0.069 to -0.038; p < .0001), as well as an average of 0.54 years of life loss at the age of 45 and 0.49 years of life loss at the age of 60, compared to those who were not exposed to any early life risk factors. Early life factors including maternal smoking, non-breastfed, low birth weight, and shorter height compared to peers at age 10 were associated with shorter TL in later life. In addition, an increased number of the aforementioned factors was associated with a greater likelihood of shorter TL in adulthood, as well as a reduced life expectancy.

Associations of childhood and adulthood body size, and child-to-adult body size change with adult telomere length.

To comprehensivelyexamine the associations of childhood and adulthood body size, and child-to-adult body size change with adult leucocyte telomere length (LTL). We included 453 602 participants from the UK Biobank. Childhood body size at the age of 10 years was collected through a questionnaire. Adulthood body size was assessed using body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), fat mass index (FMI), and fat-free mass index (FFMI). Individuals with plumper body size in childhood exhibited shorter LTL in adulthood (-0.0086 [-0.0017, -0.0004]). Adulthood BMI (-0.0286 [-0.0315, -0.0258]), WC (-0.0271 [-0.0303, -0.0238]), WHR (-0.0269 [-0.0308, -0.0230]) and FMI (-0.0396 [-0.0438, -0.0351]) were negatively associated with LTL, whereas FFMI (0.0095 [0.0039, 0.0152]) was positively associated with LTL. Compared to individuals consistently having an average/normal weight in both childhood and adulthood, those who maintained or developed overweight/obesity from childhood to adulthood had a shorter adult LTL, regardless of childhood body size. Notably, the LTL shortening effect was not observed in individuals with plumper body size in childhood but normal weight in adulthood. Childhood and adulthood obesity are both associated with LTL shortening in adulthood. Transitioning to or maintaining overweight/obese status from childhood to adulthood is associated with shorter adult LTL, whereas this effect can be reversed if plumper children become normal weight.

Maternal smoking during pregnancy could accelerate aging in the adulthood: evidence from a perspective study in UK Biobank

BackgroundMaternal smoking during pregnancy (MSDP) is significantly linked to the short- or long-term health of offspring. However, little research has examined whether MSDP affect the aging rate of offspring. MethodsThis study used questionnaires to determine out whether the participants' mothers smoked when they were pregnant. For evaluating aging rate, we used the following several outcome measures: telomere length, frailty index, cognitive function, homeostatic dysregulation score, KDM-age, age-related hospitalization rate, premature death, and life expectancy. ResultAfter adjusting for covariates, we found that the offspring of the MSDP group had significantly shorter telomere length in adulthood by 0.8 % (β = −0.008,95%CI:−0.009 to −0.006) compared with non-MSDP group. Compared to the non-MSDP group, participants in MSDP group showed higher levels of homeostatic dysregulation (β = 0.015,95%CI: 0.007–0.024) and were frailer (β = 0.008,95%CI:0.007–0.009). The KDM age increased by 0.100 due to MSDP (β = 0.100,95 % CI:0.018–0.181), and the age acceleration of KDM algorithm also increases significantly (β = 0.101, 95%CI:0.020–0.183). Additionally, we found that the risk of aging-related hospitalizations was significantly higher than the non-MSDP group by 10.4 %(HR = 1.104,95%CI:1.066–1.144). Moreover, MSDP group had a 12.2 % increased risk of all-cause premature mortality (HR = 1.122,95%CI:1.064–1.182) and a significant risk of lung cancer-specific premature mortality increased by 55.4 %(HR = 1.554,95%CI:1.346–1.793). In addition, participants in the MSDP group had significantly decreased cognitive function and shorter life expectancies than those in non-MSDP group. ConclusionOur findings indicated a significant association between MSPD and accelerated aging, elevated hospitalization rates, increased premature mortality rates, and reduced life expectancies in offspring.

Adult telomere length is positively correlated with survival and lifetime reproductive success in a wild passerine.

Explaining variation in individual fitness is a key goal in evolutionary biology. Recently, telomeres, repeating DNA sequences capping chromosome ends, have gained attention as a biomarker for body state, physiological costs, and senescence. Existing research has provided mixed evidence for whether telomere length correlates with fitness, including survival and reproductive output. Moreover, few studies have examined how the rate of change in telomere length correlates with fitness in wild populations. Here, we intensively monitored an insular population of house sparrows, and collected longitudinal telomere and life history data (16 years, 1225 individuals). We tested whether telomere length and its rate of change predict fitness measures, namely survival, lifespan and annual and lifetime reproductive effort and success. Telomere length positively predicted short-term survival, independent of age, but did not predict lifespan, suggesting either a diminishing telomere length-survival correlation with age or other extrinsic factors of mortality. The positive association of telomere length with survival translated into reproductive benefits, as birds with longer telomeres produced more genetic recruits, hatchlings and reared more fledglings over their lifetime. In contrast, there was no association between telomere dynamics and annual reproductive output, suggesting telomere dynamics might not reflect the costs of reproduction in this population, potentially masked by variation in individual quality. The rate of change of telomere length did not correlate with neither lifespan nor lifetime reproductive success. Our results provide further evidence that telomere length correlates with fitness, and contribute to our understanding of the selection on, and evolution of, telomere dynamics.

Low Antioxidant Glutathione Levels Lead to Longer Telomeres: A Sex-Specific Link to Longevity?

Telomeres are repetitive DNA sequences at the end of chromosomes that protect them from degradation. They have been the focus of intense research because short telomeres would predict accelerated ageing and reduced longevity in vertebrates. Oxidative stress is considered a physiological driver of the telomere shortening and, consequently, short lifespan. Among molecules fighting against oxidative stress, glutathione is involved in many antioxidant pathways. Literature supports that oxidative stress may trigger a compensatory "hormetic" response increasing glutathione levels and telomere length. Here, we tested the link between total glutathione concentration and telomere length in captive birds (zebra finches; Taeniopygia guttata). Total glutathione levels were experimentally decreased during birds' growth using a specific inhibitor of glutathione synthesis (buthionine sulfoximine; BSO). We monitored the birds' reproductive performance in an outdoor aviary during the first month of life, and their longevity for almost 9 years. Among control individuals, erythrocyte glutathione levels during development positively predicted erythrocyte telomere length in adulthood. However, BSO-treated females, but not males, showed longer telomeres than control females in adulthood. This counterintuitive finding suggests that females mounted a compensatory response. Such compensation agrees with precedent findings in the same population where the BSO treatment increased growth and adult body mass in females but not males. BSO did not influence longevity or reproductive output in any sex. However, early glutathione levels and adult telomere length interactively predicted longevity only among control females. Those females with "naturally" low (non-manipulated) glutathione levels at the nestling age but capable of producing longer telomeres in adulthood seem to live longer. The results suggest that the capability to mount a hormetic response triggered by low early glutathione levels can improve fitness via telomere length. Overall, the results may indicate a sex-specific link between glutathione and telomere values. Telomerase activity and sexual steroids (estrogens) are good candidates to explain the sex-biased mechanism underlying the early-life impact of oxidative stress on adult telomere length.

Association of Newborn Telomere Length With Blood Pressure in Childhood

Adult telomere length (TL) is a biological marker of aging associated with vascular health. TL at birth is associated with later life TL and may contain early biological information of later life cardiovascular health and disease. To evaluate whether newborn TL is associated with early life blood pressure differences in childhood. This cohort study was part of the ENVIRONAGE (Environmental Influence on Aging in Early Life) study, a birth cohort of Belgian mother-child pairs with recruitment at birth and a median follow-up of 4.5 years conducted between October 2014 and July 2021. Participants included for analysis provided full data for evaluation at follow-up visit. Data analysis was conducted between August and September 2021. Cord blood and placental average relative TL were measured at birth using quantitative polymerase chain reaction (qPCR). Systolic, diastolic, and mean arterial pressure (MAP) were evaluated at follow-up. High childhood blood pressure (standardized for child age, sex, and height) was defined following the 2017 American Academy of Pediatrics guidelines. Multivariable adjusted linear and logistic regression models were used to associate newborn TL and blood pressure indicators in childhood. This study included 485 newborn children (52.8% girls) with a mean (SD) age of 4.6 (0.4) years at the follow-up visit. Newborn TL was associated with lower blood pressure in childhood. A 1-IQR increase in cord blood TL was associated with a -1.54 mm Hg (95% CI, -2.36 to -0.72 mm Hg) lower diastolic blood pressure and -1.18 mm Hg (95% CI, -1.89 to -0.46 mm Hg) lower MAP. No association was observed with systolic blood pressure. Furthermore, a 1-IQR increase in cord blood TL was associated with lower odds of having high blood pressure at the age of 4 to 6 years (adjusted OR, 0.72; 95% CI, 0.53 to 0.98). In placenta, a 1-IQR increase in TL was associated with a -0.96 mm Hg (95% CI, -1.72 to -0.21 mm Hg) lower diastolic, -0.88 mm Hg (95% CI, -1.54 to -0.22 mm Hg) lower MAP, and a lower adjusted OR of 0.69 (95% CI, 0.52 to 0.92) for having a high blood pressure in childhood. In this prospective birth cohort study, variation in early life blood pressure at school-age was associated with TL at birth. Cardiovascular health may to some extent be programmed at birth, and these results suggest that TL entails a biological mechanism in this programming.

Early life trauma and adult leucocyte telomere length

BackgroundTelomere length, a biomarker of cell division and cellular aging, has been associated with multiple chronic disease endpoints. Experienced trauma over the life course may contribute to telomere shortening via mechanisms of stress embodiment. However, it is unclear how patterns of co-occurring trauma during sensitive periods (e.g., early life) throughout the life course may influence telomere shortening. We examine the relationship between co-occurring early life trauma on adult telomere length and the extent to which adulthood trauma, socioeconomic position, and health and lifestyle factors may mediate this relationship. MethodsWe use data from a sample of participants in the Sister Study (N = 740, analytic sample: n = 602), a prospective cohort of U.S. self-identified females aged 35–74 years at enrollment (2003–2009) for whom leukocyte telomere length was measured in baseline blood samples. Participants reported their experience of 20 different types of trauma, from which we identified patterns of co-occurring early life trauma (before age 18) using latent class analysis. We estimated the direct and indirect effects of early life trauma on leukocyte telomere length using structural equation modeling, allowing for mediating adult pathways. ResultsApproximately 47 % of participants reported early life trauma. High early life trauma was associated with shorter telomere length compared to low early life trauma (β = −0.11; 95 % CI: −0.22, −0.004) after adjusting for age and childhood socioeconomic position. The inverse association between early life trauma and adult leukocyte telomere length was largely attributable to the direct effect of early life trauma on telomere length (β = −0.12; 95 %CI: −0.23, −0.01). Mediating indirect pathways via adult trauma, socioeconomic position, and health metrics did not substantively contribute the overall association. ConclusionsThese findings highlight the role of patterns of co-occurring early life trauma on shortened telomere length independent of adult pathways.

Seychelles warblers with silver spoons: Juvenile body mass is a lifelong predictor of annual survival, but not annual reproduction or senescence.

The environment experienced during development, and its impact on intrinsic condition, can have lasting outcomes for individual phenotypes and could contribute to variation in adult senescence trajectories. However, the nature of this relationship in wild populations remains uncertain, owing to the difficulties in summarizing natal conditions and in long‐term monitoring of individuals from free‐roaming long‐lived species. Utilizing a closely monitored, closed population of Seychelles warblers (Acrocephalus sechellensis), we determine whether juvenile body mass is associated with natal socioenvironmental factors, specific genetic traits linked to fitness in this system, survival to adulthood, and senescence‐related traits. Juveniles born in seasons with higher food availability and into smaller natal groups (i.e., fewer competitors) were heavier. In contrast, there were no associations between juvenile body mass and genetic traits. Furthermore, size‐corrected mass—but not separate measures of natal food availability, group size, or genetic traits—was positively associated with survival to adulthood, suggesting juvenile body mass is indicative of natal condition. Heavier juveniles had greater body mass and had higher rates of annual survival as adults, independent of age. In contrast, there was no association between juvenile mass and adult telomere length attrition (a measure of somatic stress) nor annual reproduction. These results indicate that juvenile body mass, while not associated with senescence trajectories, can influence the likelihood of surviving to old age, potentially due to silver‐spoon effects. This study shows that measures of intrinsic condition in juveniles can provide important insights into the long‐term fitness of individuals in wild populations.

Prenatal exposure to maternal psychological distress and telomere length in childhood.

Telomere length (TL) is a biological marker of cellular aging, and shorter TL in adulthood is associated with increased morbidity and mortality risk. It is likely that these differences in TL are established long before adulthood, and there is growing evidence that TL can reflect prenatal experiences. Although maternal prenatal distress predicts newborn TL, it is unknown whether the relation between prenatal exposure to maternal distress and child TL persists through childhood. The purpose of the current longitudinal, prospective study is to examine the relation between prenatal exposure to maternal distress (perceived stress, depressive symptoms, pregnancy-related anxiety) and TL in childhood. Participants included 102 children (54 girls) and their mothers. Mothers' distress was assessed five times during pregnancy, at 12weeks postpartum, and at the time of child telomere measurement between 6 and 16 years of age. Maternal distress during pregnancy predicted shorter offspring TL in childhood, even after accounting for postnatal exposure to maternal distress and other covariates. These findings indicate that maternal mental health predicts offspring TL biology later in childhood than previously observed. This study bolsters claims that telomere biology is subject to fetal programming and highlights the importance of supporting maternal mental health during pregnancy.

Population differences in the length and early-life dynamics of telomeres among European pied flycatchers.

Telomere length and shortening rate are increasingly being used as biomarkers for long-term costs in ecological and evolutionary studies because of their relationships with survival and fitness. Both early-life conditions and growth, and later-life stressors can create variation in telomere shortening rate. Studies on between-population telomere length and dynamics are scarce, despite the expectation that populations exposed to varying environmental constraints would present divergent telomere length patterns. The pied flycatcher (Ficedula hypoleuca) is a passerine bird breeding across Eurasia (from Spain to western Siberia) and migrating through the Iberian Peninsula to spend the nonbreeding period in sub-Saharan Africa. Thus, different populations show marked differences in migration distance. We studied the large-scale variation of telomere length and early-life dynamics in the pied flycatcher by comparing six European populations across a north-south gradient (Finland, Estonia, England and Spain) predicting a negative effect of migration distance on adult telomere length, and of nestling growth on nestling telomere dynamics. There were clear population differences in telomere length, with English birds from midlatitudes having the longest telomeres. Telomere length did not thus show consistent latitudinal variation and was not linearly linked to differences in migration distance. Early-life telomere shortening rate tended to vary between populations. Fast growth was associated with shorter telomeres in the early life, but faster nestling growth affected telomeres more negatively in northern than southern populations. While the sources of between-population differences in telomere-related biology remain to be more intensively studied, our study illustrates the need to expand telomere studies at the between-population level.

Relationships Between Telomere Length, Plasma Glucagon-like Peptide 1, and Insulin in Early-Life Stress–Exposed Nonhuman Primates

BackgroundEarly-life stress is associated with alterations in telomere length, a marker of accumulated stress and aging, and a risk factor for psychiatric disorders. Nonhuman primate maternal variable foraging demand (VFD) is a validated early-life stress model, resulting in anxiety- and depressive-like symptoms in offspring. Previous studies reported increased plasma glucagon-like peptide 1 (pGLP-1) along with insulin resistance in this model. We investigated whether VFD rearing related to adult telomere length and to these neuroendocrine markers. MethodsAdult leukocyte telomere length was measured in VFD-reared (12 males, 13 females) and non-VFD–reared (9 males, 26 females) bonnet macaques. Associations between adult telomere length and adolescent fasting pGLP-1 or insulin resistance in VFD-reared versus non-VFD–reared groups were examined using regression modeling, controlling for sex, weight, and age. ResultsVFD subjects had relatively longer telomeres than non-VFD subjects (p = .017), and females relatively longer than males (p = .0004). Telomere length was positively associated with pGLP-1 (p = .0009) and with reduced insulin sensitivity (p < .0001) in both sexes, but not as a function of rearing group. ConclusionsUnexpectedly, VFD was associated with longer adult telomere length. Insulin resistance may lead to higher pGLP-1 levels in adolescence, which could protect telomere length in VFD offspring as adults. Associations between adult telomere length and adolescent insulin resistance and high pGLP-1 may reflect an adaptive, compensatory response after early-life stress exposure.

Pilot Study of Absolute Telomere Lengths in Preterm Infants.

Annually, approximately 15 million babies are born preterm (<37 weeks gestational age) globally. In the neonatal intensive care unit (NICU) environment, infants are exposed to repeated stressful or painful procedures as part of routine lifesaving care. These procedures have been associated with epigenetic alterations that may lead to an increased risk of neurodevelopmental disorders. Telomere length has been negatively associated with adverse life experiences in studies of adults. This pilot study aimed to describe telomere length in a sample of preterm infants at NICU discharge and examine any associations with pain, feeding method, and neurodevelopment. This descriptive pilot study sample includes baseline absolute telomere length (aTL) of 36 preterm infants immediately prior to discharge. Quantitative polymerase chain reaction was used to determine aTL. Infant demographics, pain/stress, type of feeding, antibiotic use, neurodevelopment, and buccal swab data were collected. Descriptive data analysis was used to describe the telomere length using graphs. Among our preterm infant samples, the mean aTL was far greater than the average adult telomere length. Although no significant associations were found between aTL and pain, feeding method, and neurodevelopment, a trend between sex was noted where male telomere lengths were shorter than females as they aged. This is one of few studies to evaluate preterm infant telomere length. Although other researchers have used relative telomere length, we used the more accurate aTL. We found nonsignificant shorter telomere lengths among males. Additional large-scale, longitudinal studies are needed to better identify the predictors of telomere length at the time of discharge from NICU.

Individual telomere dynamics and their links to life history in a viviparous lizard

Emerging patterns suggest telomere dynamics and life history are fundamentally linked in endotherms through life-history traits that mediate the processes underlying telomere attrition. Unlike endotherms, ectotherms maintain the ability to lengthen somatic telomeres throughout life and the link between life-history strategies and ectotherm telomere dynamics is unknown. In a well-characterized model system (Niveoscincus ocellatus), we used long-term longitudinal data to study telomere dynamics across climatically divergent populations. We found longer telomeres in individuals from the cool highlands than those from the warm lowlands at birth and as adults. The key determinant of adult telomere length across populations was telomere length at birth, with population-specific effects of age and growth on adult telomere length. The reproductive effort had no proximate effect on telomere length in either population. Maternal factors influenced telomere length at birth in the warm lowlands but not the cool highlands. Our results demonstrate that life-history traits can have pervasive and context-dependent effects on telomere dynamics in ectotherms both within and between populations. We argue that these telomere dynamics may reflect the populations' different life histories, with the slow-growing cool highland population investing more into telomere lengthening compared to the earlier-maturing warm lowland population.

Telomere length is heritable and genetically correlated with lifespan in a wild bird.

Telomeres are protective caps at the end of eukaryotic chromosomes that shorten with age and in response to stressful or resource-demanding conditions. Their length predicts individual health and lifespan across a wide range of animals, but whether the observed positive association between telomere length and lifespan is environmentally induced, or set at conception due to a shared genetic basis, has not been tested in wild animals. We applied quantitative genetic "animal models" to longitudinal telomere measurements collected over a 10-year period from individuals of a wild seabird (common tern; Sterna hirundo) with known pedigree. We found no variation in telomere shortening with age among individuals at the phenotypic and genetic level, and only a small permanent environmental effect on adult telomere length. Instead, we found telomere length to be highly heritable and strongly positively genetically correlated with lifespan. Such heritable differences between individuals that are set at conception may present a hitherto underappreciated component of variation in somatic state.

Intergenerational Trauma Transmission? Test of Cellular Aging in Mothers Exposed to Sexual Abuse and Their Children

Exposure to maltreatment during childhood can lead to increased risk for poor health outcomes in adulthood. Child maltreatment and later poor health may be linked by premature biological aging. We tested whether childhood sexual abuse (CSA) is associated with telomere length (TL) in adult females. We further tested the hypothesis of intergenerational transmission of trauma by measuring TL in both CSA-exposed and non-exposed mothers and their children. TL was measured in a subset of participants and their children from a prospective-longitudinal cohort study of sexually abused females and a demographically matched comparison group. Linear regression models were used to test for associations between CSA-exposure and age-adjusted TL in females (N=108, mean age 36.3 years). Multilevel linear models were used to test the intergenerational effect of maternal-CSA exposure on age-adjusted TL in their children (N=124 children mean age 10.5 years across 61 mothers). CSA-exposure was not associated with TL in females. Replicating previous work in this area, maternal TL and sex were significant predictors of child TL in all models tested. Longer maternal TL predicted longer TL in children, and female children had longer TL than male children. Maternal-CSA exposure did not predict TL in children. This finding is in line with some previous results on CSA and TL measured in adulthood. Previous significant results associating child maltreatment with shorter TL in adulthood may be capturing a population of individuals exposed to either multiple types of maltreatment or maltreatment in childhood with concurrent TL measurements.

No sex differences in adult telomere length across vertebrates: a meta-analysis.

In many mammalian species, females live on average longer than males. In humans, women have consistently longer telomeres than men, and this has led to speculation that sex differences in telomere length (TL) could play a role in sex differences in longevity. To address the generality and drivers of patterns of sex differences in TL across vertebrates, we performed meta-analyses across 51 species. We tested two main evolutionary hypotheses proposed to explain sex differences in TL, namely the heterogametic sex disadvantage and the sexual selection hypotheses. We found no support for consistent sex differences in TL between males and females among mammal, bird, fish and reptile species. This absence of sex differences in TL across different classes of vertebrates does not support the heterogametic sex disadvantage hypothesis. Likewise, the absence of any negative effect of sexual size dimorphism on male TL suggests that sexual selection is not likely to mediate the magnitude of sex differences in TL across vertebrates. Finally, the comparative analyses we conducted did not detect any association between sex differences in TL and sex differences in longevity, which does not support the idea that sex differences in TL could explain the observed sex differences in longevity.

Extremely low birth weight influences the relationship between stress and telomere length in adulthood.

This study examined the link between two biological markers of stress vulnerability at 22-26 years of age and telomere length at 30-35 among extremely low birth weight (ELBW; <1000 g) survivors and normal birth weight (NBW; >2500 g) control participants. Sixteen ELBW and 22 NBW participants provided baseline afternoon salivary cortisol samples and resting frontal electroencephalogram (EEG) alpha asymmetry data at 22-26 years. Buccal cells were assayed for telomere length at 30-35 years. Analyses controlled for sex, postnatal steroid exposure, childhood socioeconomic status, time of cortisol sample collection, and body mass index at 22-26 years. Salivary cortisol and frontal asymmetry at age 22-26 independently predicted telomere length at age 30-35, such that relatively higher cortisol and greater relative right frontal asymmetry at rest predicted telomere shortening among NBW controls, but not among ELBW survivors. However, similar associations were not noted in ELBW survivors, suggesting that ELBW survivors may have different mechanisms of stress coping as a result of their early-life exposures. These findings offer preliminary evidence in support of the role of stress in the genesis of cellular senescence at least among those born at NBW, but that these links may differ in those born preterm.

Telomere length is repeatable, shortens with age and reproductive success, and predicts remaining lifespan in a long-lived seabird.

Telomeres are protective caps at the end of chromosomes, and their length is positively correlated with individual health and lifespan across taxa. Longitudinal studies have provided mixed results regarding the within-individual repeatability of telomere length. While some studies suggest telomere length to be highly dynamic and sensitive to resource-demanding or stressful conditions, others suggest that between-individual differences are mostly present from birth and relatively little affected by the later environment. This dichotomy could arise from differences between species, but also from methodological issues. In our study, we used the highly reliable Terminal Restriction Fragment analysis method to measure telomeres over a 10-year period in adults of a long-lived seabird, the common tern (Sterna hirundo). Telomeres shortened with age within individuals. The individual repeatability of age-dependent telomere length was high (>0.53), and independent of the measurement interval (i.e., one vs. six years). A small (R2 =.01), but significant part of the between-individual variation in telomere length was, however, explained by the number of fledglings produced in the previous year, while reproduction in years prior to the previous year had no effect. We confirmed that age-dependent telomere length predicted an individual's remaining lifespan. Overall, our study suggests that the majority of between-individual variation in adult telomere length is consistent across adult life, and that a smaller part of the variation can be explained by dynamic factors, such as reproduction.

Association between socioeconomic markers and adult telomere length differs according to sex: Pro-Saúde study.

Understanding the social determinants of telomere length is critical to evaluate the risk of early biological aging. We investigated sex differences on the association between socioeconomic status (SES) and demographic markers and leukocyte telomere length (LTL) in Brazilian adults. This cross-sectional study was conducted in a subsample (women=228; men=200) nested within the Pro-Saúde study, a prospective cohort study of university civil servants in Rio de Janeiro, Brazil (2012-2013). Adjusted multivariate models were used to test the relationship between SES markers (marital status, educational attainment, father's educational attainment, race/skin color, household income, and childhood experience of food deprivation) and LTL. After adjusting for age and potential health-related confounders, lower educational attainment was associated with shorter LTL among men (β=-0.05, 95% confidence interval (CI)=95%CI: -0.10, 0.00, P=0.03). In women, LTL was inversely associated with unmarried status (β=-0.05, 95%CI: -0.09, 0.00, P=0.03), lower father's educational attainment (β=-0.05, 95%CI: -0.13, 0.00, P=0.04), and childhood experience of food deprivation (β=-0.07, 95%CI: -0.13, 0.00, P=0.04). Our findings suggested that the association between SES markers and LTL differs according to sex. SES markers able to induce lifelong stress, reflected in LTL, appeared to be more related to individual factors in men, whereas in women they were family-related.