Emerging Trends in The Social and Behavioral Sciences

Telomeres

Item

Title

Telomeres

Author

Adler, Nancy

O'Donovan, Aoife

Research Area

Special Areas of Interdisciplinary Study

Topic

Genetics, the Individual and Society

Abstract

Telomeres cap the ends of chromosomes in the cell and their length provides a marker of cellular aging. As people age, their telomeres generally shorten, a process that is accelerated by exposure to chronic stress as well as by health behaviors such as smoking, lack of exercise, and poor diet. Individuals who are lower on the social hierarchy have shorter telomeres on average, providing evidence of the health‐damaging effects of social disadvantage.

Related Essays

Social Epigenetics: Incorporating Epigenetic Effects as Social Cause and Consequence (Sociology), Douglas L. Anderton and Kathleen F. Arcaro

Inefficiencies in Health Care Provision (Economics), James F. Burgess et al.

Self-Fulfilling Prophesies, Placebo Effects, and the Social-Psychological Creation of Reality (Sociology), Alia Crum and Damon J. Phillips

Genetic and Environmental Approaches to Political Science (Political Science), Zoltán Fazekas and Peter K. Hatemi

Evolutionary Approaches to Understanding Children's Academic Achievement (Psychology), David C. Geary and Daniel B. Berch

Genetics and Social Behavior (Anthropology), Henry Harpending and Gregory Cochran

An Evolutionary Perspective on Developmental Plasticity (Psychology), Sarah Hartman and Jay Belsky

Niche Construction: Implications for Human Sciences (Anthropology), Kevin N. Laland and Michael O'Brien

Immigrant Health Paradox (Sociology), Kyriakos S. Markides and Sunshine Rote

Rationing of Health Care (Sociology), David Mechanic

Health and Social Inequality (Sociology), Bernice A. Pescosolido

Social Relationships and Health in Older Adulthood (Psychology), Theodore F. Robles and Josephine A. Menkin

The Role of Cultural, Social, and Psychological Factors in Disease and Illness (Sociology), Robert A. Scott

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Identifier

etrds0329

extracted text

Telomeres
NANCY ADLER and AOIFE O’DONOVAN

Abstract
Telomeres cap the ends of chromosomes in the cell and their length provides a marker
of cellular aging. As people age, their telomeres generally shorten, a process that
is accelerated by exposure to chronic stress as well as by health behaviors such as
smoking, lack of exercise, and poor diet. Individuals who are lower on the social hierarchy have shorter telomeres on average, providing evidence of the health-damaging
effects of social disadvantage.

INTRODUCTION
Biomarkers alert patients and providers to incipient disease to allow early
intervention and monitor the efficacy of treatment. For example, elevated levels of glycated hemoglobin (HbA1c), reflecting the concentration of glucose
in the blood, signals increased risk of diabetes and may trigger attempts to
reduce risk through diet, exercise, and weight loss. If diabetes occurs, HbA1c
levels help monitor whether health behaviors and/or pharmaceutical treatments are effective in controlling the disorder. Biomarkers also provide information on the health of populations and enable us to link social factors to
internal biological process that can affect health.
Biomarkers are frequently used to assess stress responses and assess the
extent to which social circumstances trigger and modify these responses.
Most commonly used is cortisol, a hormone that mobilizes resources to allow
the body to activate “fight or flight” responses to deal with an immediate
threat. Cortisol levels have been linked to a range of social factors including low social rank in nonhuman primates, negative social evaluations in
laboratory settings, and low income. However, cortisol is more useful as a
measure of acute stress than of chronic stress and researchers have sought a
more stable biomarker that can better inform us about cumulative lifespan
effects.

Emerging Trends in the Social and Behavioral Sciences. Edited by Robert Scott and Stephen Kosslyn.
© 2015 John Wiley & Sons, Inc. ISBN 978-1-118-90077-2.

1

2

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

In this context, telomere length, a biomarker for cellular aging, has emerged
as a highly promising candidate. Unlike biomarkers that capture byproducts
of biological responses in specific systems, telomere length in white blood
cells may capture cumulative processes at the cellular and molecular level
throughout the body. White blood cells comprise various types of immune
cells that circulate in the system and serve important immune system
functions across bodily systems and tissues. Although it has not been
unequivocally shown that telomere attrition is a mechanism by which social
disadvantage leads to earlier development of chronic age-related diseases
and higher rates of mortality, white blood cell telomere length has been
linked both to experiences of chronic stress and disadvantage, and to
increased risk for specific diseases and mortality. We focus primarily on
disadvantage resulting from low socioeconomic status as reflected in low
income and education.
FOUNDATIONAL RESEARCH
TELOMERES
Telomeres are DNA–protein complexes that form protective caps on the ends
of chromosomes. Analogous to how the cap on the end of a shoelace protects
it from unraveling and fraying, the telomere on the tip of the chromosome
protects against damage to the DNA that encodes our genes. Over time, as
cells divide and are subject to biochemical stress, telomeres shorten. When
their length falls below a certain critical threshold, cells can become functionally impaired and unable to divide, and can undergo apoptosis or cell
death. Telomere length has been described as a “molecular clock” and the
shortening of telomeres with age is thought to play a mechanistic role in
age-related functional decline and increased risk for disease.
The number of studies of telomeres in humans has grown since the dawn
of the 21st Century. Such research has been facilitated by the fact that
telomeres in white blood cells can be easily measured in blood samples.
Although we do not yet know how strongly correlated telomeres from
white blood cells are with telomeres from other cell types, white blood
cell telomere length has emerged as a powerful biomarker. Prospective
studies have shown that individuals with shorter white blood cell telomeres
are more likely to develop age-related diseases such as cardiovascular
disease (including myocardial infarction and stroke), some types of cancer,
autoimmune disorders, and dementia.
The precise causes of telomere shortening in humans are not fully understood. However, there is evidence that telomere shortening is accelerated by
oxidative stress, the imbalance between oxidizing molecules and antioxidant

Telomeres

3

defenses, and by chronic activation of the inflammatory response of the
immune system. There is also some evidence that high levels of the stress
hormone cortisol may downregulate processes that maintain telomeres.
Oxidative stress and chronic inflammation, which are linked to greater
telomere attrition, are elevated among individuals who smoke, are physically
inactive and/or have high body mass index. Because socially disadvantaged
groups show higher rates of all these risk factors, they may be a pathway
by which social factors get into the body to affect health and longevity. In
addition, socially disadvantaged individuals experience greater chronic
psychological stress, which can also increase inflammation and oxidative
stress, may accelerate telomere attrition.
Stress and Telomere Length. Accumulating evidence links psychological stress
exposure with short telomere length. A groundbreaking study found shorter
telomeres among women experiencing greater distress as a result of caring
for a chronically ill child, and the longer the duration of the caregiving, the
shorter her telomeres. Subsequent studies have linked shorter telomeres to
other chronic stresses across the lifespan. One study found shorter telomeres
in the adult offspring of women who were exposed to stress during pregnancy. Another found a faster rate of telomere shortening from age 5 to age
10 among children exposed to maternal domestic violence, physical maltreatment and frequent bullying than among children without such exposure to
violence.
It is not simply exposure to threatening or stressful conditions that
leads to accelerated telomere attrition, but the individual’s appraisal and
cognitive-emotional response to the situation. For example, among the
mothers caring for a chronically ill child in the study described, shorter
telomeres were found primarily among those who experienced higher
levels of perceived psychological stress and comparison group mothers who
reported relatively high levels of perceived stress. Perceived psychological
stress appears, in fact, to be more robustly related to short telomere length
than is objective stress exposure. This stands to reason because stress gets
“under the skin” only to the extent that it activates the biological stress
response, which in turn is dependent on stress perception.
Social Determinants. Studies linking stress and telomere length suggest a possible pathway by which social disadvantage results in disease. Socially disadvantaged individuals—those with less education and lower incomes and
members of some minority groups—experience greater chronic stress. However, findings to date linking telomere length to specific aspects of social
status are mixed.

4

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Much of the research on social status and health, including telomere length,
has been done in the United Kingdom. Shorter white blood cell telomere
length was observed among British women in manual versus nonmanual
occupational classes and in unemployed versus employed Scottish men.
However, in these samples, telomere length was not associated with income
or education, or with neighborhood deprivation. In contrast, lower income
was associated with shorter telomere length in a study of Scottish men and
women, and two other studies in Britain found an association of shorter
telomere length with lower educational attainment, but not other indicators
of social disadvantage.
In the United States, studies have examined telomere length in relation to
race and ethnicity as well as to socioeconomic status. African-Americans are
exposed to greater chronic stress and have poorer health status than do other
groups. Within samples of African-Americans, the relationship between
psychological stress and short telomere length appears to hold. However,
African-Americans appear to have relatively longer telomeres than whites.
A recent study of older black and white adults demonstrated the importance
of considering the combination of race/ethnicity and socioeconomic status
in assessing telomere length. Although, overall, individuals with more than
a high school education had longer telomeres than those with a high school
education or less, this effect was moderated by race. There was relatively
little difference in telomere length by educational levels for whites, but a
marked difference for blacks. Indeed, the telomeres of blacks with more
than a high school education were not only significantly longer than those
of lesser-educated blacks but were also significantly longer than those of
whites no matter their level of education.
CUTTING-EDGE RESEARCH
MECHANISMS OF THE STRESS–TELOMERE RELATIONSHIP
The vast majority of studies linking the social environment with telomere
length focus on stress as a mediator of the association. Much research on
the health effects of chronic stress has focused on “allostatic load,” the
accumulated wear and tear on the body of repeated exposures to stress.
Allostatic load represents dysregulation of multiple systems within the body
and predicts future risk of morbidity and mortality. The same processes
that contribute to allostatic load are related to telomere shortening. Consequently, studies are currently making links between social disadvantage
and exposure to uncontrollable threatening situations on the one hand and
dysregulation of biological systems and accelerated cellular aging on the
other.

Telomeres

5

These studies reveal the biological effects of frequent cycles of threat and
disadvantage associated with lower social status. Social threats activate the
hypothalamic-pituitary-adrenal axis and increase production of cortisol and
proinflammatory proteins. These responses are functional in the short term
in preparing the body for “fight or flight” as well as for injury and infection. However, repeated and prolonged activation of these responses in the
socially disadvantaged can promote chronic biological changes that accelerate telomere shortening.
In addition to direct physiological effects of repeated and prolonged
activation of biological stress systems on telomeres, recent studies reveal an
indirect path from social status to cell aging through behavioral responses
individuals use to cope with stressful circumstances. Individuals with
fewer socioeconomic resources encounter more uncontrollable stressors
than do the more advantaged. Animal models have shown that exposure
to uncontrollable stress promotes greater ingestion of foods containing
fats and sugars. As with the stress response, this behavioral response
is functional because consuming such foods can downregulate cortisol
release. Among humans, stress-inducing exposures may not only elicit the
ingestion of energy dense “comfort foods” but also use of tobacco and
other substances. These bring short-term emotional relief and can dampen
down the stress response, but over time, can damage telomeres and the
body.
Individuals who have encountered repeated exposures to threatening and
uncontrollable situations may become more vigilant for information that
may signal potential threats. Such vigilance is advantageous in dangerous
environments. However, sensitivity to threat can be costly, leading to more
frequent and prolonged activation of biological stress systems even when
threats are absent or mild. When adolescents from different socioeconomic
backgrounds were asked to interpret videos of various kinds of social situations they made similar interpretations of clearly positive or clearly negative
scenarios. However, adolescents from families of lower socioeconomic
status interpreted ambiguous situations as more threatening than did their
more advantaged peers. Adolescents making more negative attributions to
ambiguous videos appeared to pay a price for their vigilance, exhibiting
higher blood pressure in overnight monitoring.
Biological stress responses to anticipated and actual threat—both of which
may be more common in socially disadvantaged individuals—may promote
telomere shortening. This pathway would explain recent finding that
women who rated a standardized acute laboratory stressor as more threatening had significantly shorter telomeres than those making more benign
appraisals.

6

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Buffers of the Stress–Telomere Relationship. Although stress appears to accelerate telomere shortening, individuals who are experiencing chronic stress may
be able to lessen its impact on their telomeres through engagement in healthy
behaviors. For example, physical activity may slow telomere attrition, especially in the face of stress. In one study, women who were physically active
showed no relationship between their reported levels of stress and the length
of their telomeres, while among those who did not exercise, those reporting
greater stress had significantly shorter telomeres.
Emerging evidence indicates that a lifestyle including physical activity,
good sleep and a diet enriched with fresh fruit and vegetables and lower
processed meat intake may slow telomere attrition. An important next
step will be translating findings into effective interventions. This will be
challenging. It is difficult to get people to maintain a healthy lifestyle, and
even more so when people are enduring high stress that requires attention
to immediate survival goals and emotional needs. Moreover, individuals
who are from socially disadvantaged groups have more limited access to
resources for engaging in health-promoting behaviors.
KEY ISSUES FOR FUTURE RESEARCH
TELOMERE LENGTHENING
One of the most exciting but also puzzling stories to have emerged in the
telomere field in recent years is the finding that telomeres may lengthen as
well as shorten. Although telomeres are longest at birth and shortest in old
age, accumulating evidence suggests that some individuals show telomere
lengthening over periods ranging from 1 to 5 years. The enzyme telomerase,
a reverse transcriptase that builds telomeric DNA and lengthens telomeres, may be responsible for this occurrence. In cells cultured in the laboratory, telomeres shorten with each cycle of cell division until they reach a
critical shortness called the Hayflick limit. At this critical point, cells become
functionally impaired and are unable to divide and produce daughter
cells. However, when telomerase is added to such cultures, telomeres are
maintained for longer, allowing the cells to continue dividing. This process
is tightly regulated to allow for damaged and older cells to die and leave the
system. The exception is found in cancer cells, which have short telomeres,
but can become immortal by expressing very high levels of telomerase.
Thus, at the same time that telomerase is beneficial in allowing healthy cells
to stay functional and proliferate, it can also be problematic by promoting
thriving in cancer cells.
In general, however, higher levels of telomerase are associated with better health in humans, suggesting that increased telomerase is advantageous

Telomeres

7

overall. For example, when prostate cancer patients engaged in comprehensive lifestyle improvements, their levels of telomerase increased. Physical
activity also activates telomerase and there are recent reports that mindfulness meditation interventions increase telomerase. Future studies are needed
to understand the factors that promote telomerase activity, and to elucidate
its ability to slow biological aging.
TELOMERE LENGTH MEASUREMENT
Telomere length is generally assessed from white blood cells using either
the “Southern blot” or the “quantitative real-time polymerase chain reaction” (Q-PCR) approach. Southern blot was the first method established for
telomere length measurement and subsequent developments have increased
its sensitivity. It serves as the “gold standard” for calibrating new methods,
but it is costly and labor intensive and requires a large amount of DNA. In
contrast, the Q-PCR approach and monochrome multiplex Q-PCR methods
require less DNA and lend themselves to the high throughput needed for
large studies.
More recent and more controversial is the use of buccal cells rather than
blood to assess telomere length. Buccal cells, obtained through cheek swabs,
are easier to obtain and may be more acceptable, especially in work with
children, than is collecting blood. Advances in telomere measurement from
dried blood spots also have the potential to reduce the burden of collecting
blood samples, especially in nonclinical settings.
Recent studies show that telomere length varies even within cells, and suggest that the shortest telomere within a cell may play a particularly important
role in influencing cell responses. Thus, newer approaches to telomere length
measurement that allow the measurement of individual telomeres and the
quantification of short telomeres within cells are likely to yield important
new insights.
PUBLIC HEALTH IMPLICATIONS
Research linking social disadvantage with telomere length provides a strong
foundation for designing interventions to improve health and diminish disparities, but much remains to be done before the findings can be translated
into real-world applications. We do not yet know how and when to intervene
to slow down cellular aging. While biological researchers seek ways to target the telomere maintenance system directly, social and behavioral scientists
may find ways to slow telomere shortening by improving social conditions
and/or psychological and behavioral responses to disadvantage. Such interventions need to be informed by knowledge of modifiable mechanisms of

8

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

telomere shortening, the conditions that foster these mechanisms and the
policies that can affect these conditions.
Greater understanding of the dynamics of telomere shortening over the
life course can inform the timing and targets of interventions. Most research
on telomeres has been in older people because diseases of aging linked to
telomere shortening occur in this population. However, strategies that affect
early-life determinants of telomere length may have a greater payoff. The
length of a person’s telomeres in older adulthood is a function of the length
of the telomeres with which they were endowed at conception as well as by
environmental exposures from the womb onward. Investment in enhancing
the early-life environment may hold much promise in changing trajectories
and promoting longevity and better health into old age.
FURTHER READING
Adler, N. E., & Stewart, J. (2010). Health disparities across the lifespan: Meaning,
methods, and mechanisms. Annals of the New York Academy of Sciences, 1186, 5–23.
Adler, N., Pantell, M., O’Donovan, A., Blackburn, E. H., Cawthon, R., Koster, A.,
… , Epel, E. (2013). Educational attainment and late life telomere length in the
health, aging and body composition study. Brain, Behavior, and Immunity, 27, 15–21.
10.1016/j.bbi.2012.08.014
Aubert, G., Hills, M., & Lansdorp, P. M. (2012). Telomere length measurementCaveats and a critical assessment of the available technologies and tools. Mutation
Research, 730, 59–67.
Entringer, S., Epel, E. S., Kumsta, R., Lin, J., Hellhammer, D. H., Blackburn, E. H., … ,
Wadhwa, P. D. (2011). Stress exposure in intrauterine life is associated with shorter
telomere length in young adulthood. Proceedings of the National Academy of Sciences
of the United States of America, 108(33), E513–518.
Epel, E. S., Blackburn, E. H., Lin, J., Dhabhar, F. S., Adler, N. E., Morrow, J. D., &
Cawthon, R. M. (2004). Accelerated telomere shortening in response to life stress.
Proceedings of the National Academy of Sciences of the United States of America, 101(49),
17312–17315.
Puterman, E., Lin, J., Blackburn, E., O’Donovan, A., Adler, N., & Elissa, E. (2010). The
power of exercise: Buffering the effect of chronic stress on telomere length. PLoS
ONE, 5(5), e10837. doi:10.1371/journal.pone.0010837
Shalev, I. (2012). Early life stress and telomere length: Investigating the connection
and possible mechanisms: A critical survey of the evidence base, research methodology and basic biology. Bioessays, 34, 943–952.

NANCY ADLER SHORT BIOGRAPHY
Nancy Adler, PhD is Lisa and John Pritzker Professor of Psychology in the
Departments of Psychiatry and Pediatrics, Vice-Chair of the Department of

Telomeres

9

Psychiatry, and Director of the Center for Health and Community at the University of California, San Francisco. A social psychologist, her early research
examined the utility of decision models for understanding health behaviors
with particular focus on reproductive health. Subsequently, she directed the
MacArthur Foundation Research Network on SES and Health in which an
interdisciplinary group of researchers identified and tested possible mechanisms by which socioeconomic status gets into the body to affect health.
In addition to documenting effects of objective socioeconomic status, she
demonstrated the importance of subjective social status. A special issue of
the Annals of the New York Academy of Sciences on the Biology of Disadvantage provides an overview of this work. While continuing to conduct
empirical research on social determinants of health, she has become increasingly interested in methodological challenges in assessing the relationship
of social disadvantage and health and in policy and interventions that could
affect these processes.
AOIFE O’DONOVAN SHORT BIOGRAPHY
Aoife O’Donovan, PhD is a Society in Science—Branco Weiss Fellow and
Assistant Professor in the Department of Psychiatry at the University of
California, San Francisco, and the San Francisco Veterans Affairs Medical
Center. She received her undergraduate education in psychology and philosophy at University College Cork and subsequently completed a Masters
in Health Psychology at the National University of Ireland, Galway. During
her Masters, she conducted experimental research examining the effects
of subtle manipulations of social support on cardiovascular responses to
acute stress. Following this, she pursued a PhD in Clinical Psychobiology
at University College Dublin focused on uncovering associations between
threat-related psychological variables and indices and mechanisms of
biological aging. Dr. O’Donovan’s laboratory is focused on uncovering
how chronic and traumatic stress exposure increase risk for psychiatric
and physical disorders, by studying both the psychological and biological
consequences of stress. The ultimate goal of this work is to inform the
development of new interventions that reduce the negative effects of
psychological stress on health.
RELATED ESSAYS
Social Epigenetics: Incorporating Epigenetic Effects as Social Cause and
Consequence (Sociology), Douglas L. Anderton and Kathleen F. Arcaro
Inefficiencies in Health Care Provision (Economics), James F. Burgess et al.
Self-Fulfilling Prophesies, Placebo Effects, and the Social-Psychological
Creation of Reality (Sociology), Alia Crum and Damon J. Phillips

10

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Genetic and Environmental Approaches to Political Science (Political Science),
Zoltán Fazekas and Peter K. Hatemi
Evolutionary Approaches to Understanding Children’s Academic Achievement (Psychology), David C. Geary and Daniel B. Berch
Genetics and Social Behavior (Anthropology), Henry Harpending and Gregory Cochran
An Evolutionary Perspective on Developmental Plasticity (Psychology),
Sarah Hartman and Jay Belsky
Niche Construction: Implications for Human Sciences (Anthropology), Kevin
N. Laland and Michael O’Brien
Immigrant Health Paradox (Sociology), Kyriakos S. Markides and Sunshine
Rote
Rationing of Health Care (Sociology), David Mechanic
Health and Social Inequality (Sociology), Bernice A. Pescosolido
Social Relationships and Health in Older Adulthood (Psychology), Theodore
F. Robles and Josephine A. Menkin
The Role of Cultural, Social, and Psychological Factors in Disease and Illness
(Sociology), Robert A. Scott
Incarceration and Health (Sociology), Christopher Wildeman



Telomeres
NANCY ADLER and AOIFE O’DONOVAN

Abstract
Telomeres cap the ends of chromosomes in the cell and their length provides a marker
of cellular aging. As people age, their telomeres generally shorten, a process that
is accelerated by exposure to chronic stress as well as by health behaviors such as
smoking, lack of exercise, and poor diet. Individuals who are lower on the social hierarchy have shorter telomeres on average, providing evidence of the health-damaging
effects of social disadvantage.

INTRODUCTION
Biomarkers alert patients and providers to incipient disease to allow early
intervention and monitor the efficacy of treatment. For example, elevated levels of glycated hemoglobin (HbA1c), reflecting the concentration of glucose
in the blood, signals increased risk of diabetes and may trigger attempts to
reduce risk through diet, exercise, and weight loss. If diabetes occurs, HbA1c
levels help monitor whether health behaviors and/or pharmaceutical treatments are effective in controlling the disorder. Biomarkers also provide information on the health of populations and enable us to link social factors to
internal biological process that can affect health.
Biomarkers are frequently used to assess stress responses and assess the
extent to which social circumstances trigger and modify these responses.
Most commonly used is cortisol, a hormone that mobilizes resources to allow
the body to activate “fight or flight” responses to deal with an immediate
threat. Cortisol levels have been linked to a range of social factors including low social rank in nonhuman primates, negative social evaluations in
laboratory settings, and low income. However, cortisol is more useful as a
measure of acute stress than of chronic stress and researchers have sought a
more stable biomarker that can better inform us about cumulative lifespan
effects.

Emerging Trends in the Social and Behavioral Sciences. Edited by Robert Scott and Stephen Kosslyn.
© 2015 John Wiley & Sons, Inc. ISBN 978-1-118-90077-2.

1

2

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

In this context, telomere length, a biomarker for cellular aging, has emerged
as a highly promising candidate. Unlike biomarkers that capture byproducts
of biological responses in specific systems, telomere length in white blood
cells may capture cumulative processes at the cellular and molecular level
throughout the body. White blood cells comprise various types of immune
cells that circulate in the system and serve important immune system
functions across bodily systems and tissues. Although it has not been
unequivocally shown that telomere attrition is a mechanism by which social
disadvantage leads to earlier development of chronic age-related diseases
and higher rates of mortality, white blood cell telomere length has been
linked both to experiences of chronic stress and disadvantage, and to
increased risk for specific diseases and mortality. We focus primarily on
disadvantage resulting from low socioeconomic status as reflected in low
income and education.
FOUNDATIONAL RESEARCH
TELOMERES
Telomeres are DNA–protein complexes that form protective caps on the ends
of chromosomes. Analogous to how the cap on the end of a shoelace protects
it from unraveling and fraying, the telomere on the tip of the chromosome
protects against damage to the DNA that encodes our genes. Over time, as
cells divide and are subject to biochemical stress, telomeres shorten. When
their length falls below a certain critical threshold, cells can become functionally impaired and unable to divide, and can undergo apoptosis or cell
death. Telomere length has been described as a “molecular clock” and the
shortening of telomeres with age is thought to play a mechanistic role in
age-related functional decline and increased risk for disease.
The number of studies of telomeres in humans has grown since the dawn
of the 21st Century. Such research has been facilitated by the fact that
telomeres in white blood cells can be easily measured in blood samples.
Although we do not yet know how strongly correlated telomeres from
white blood cells are with telomeres from other cell types, white blood
cell telomere length has emerged as a powerful biomarker. Prospective
studies have shown that individuals with shorter white blood cell telomeres
are more likely to develop age-related diseases such as cardiovascular
disease (including myocardial infarction and stroke), some types of cancer,
autoimmune disorders, and dementia.
The precise causes of telomere shortening in humans are not fully understood. However, there is evidence that telomere shortening is accelerated by
oxidative stress, the imbalance between oxidizing molecules and antioxidant

Telomeres

3

defenses, and by chronic activation of the inflammatory response of the
immune system. There is also some evidence that high levels of the stress
hormone cortisol may downregulate processes that maintain telomeres.
Oxidative stress and chronic inflammation, which are linked to greater
telomere attrition, are elevated among individuals who smoke, are physically
inactive and/or have high body mass index. Because socially disadvantaged
groups show higher rates of all these risk factors, they may be a pathway
by which social factors get into the body to affect health and longevity. In
addition, socially disadvantaged individuals experience greater chronic
psychological stress, which can also increase inflammation and oxidative
stress, may accelerate telomere attrition.
Stress and Telomere Length. Accumulating evidence links psychological stress
exposure with short telomere length. A groundbreaking study found shorter
telomeres among women experiencing greater distress as a result of caring
for a chronically ill child, and the longer the duration of the caregiving, the
shorter her telomeres. Subsequent studies have linked shorter telomeres to
other chronic stresses across the lifespan. One study found shorter telomeres
in the adult offspring of women who were exposed to stress during pregnancy. Another found a faster rate of telomere shortening from age 5 to age
10 among children exposed to maternal domestic violence, physical maltreatment and frequent bullying than among children without such exposure to
violence.
It is not simply exposure to threatening or stressful conditions that
leads to accelerated telomere attrition, but the individual’s appraisal and
cognitive-emotional response to the situation. For example, among the
mothers caring for a chronically ill child in the study described, shorter
telomeres were found primarily among those who experienced higher
levels of perceived psychological stress and comparison group mothers who
reported relatively high levels of perceived stress. Perceived psychological
stress appears, in fact, to be more robustly related to short telomere length
than is objective stress exposure. This stands to reason because stress gets
“under the skin” only to the extent that it activates the biological stress
response, which in turn is dependent on stress perception.
Social Determinants. Studies linking stress and telomere length suggest a possible pathway by which social disadvantage results in disease. Socially disadvantaged individuals—those with less education and lower incomes and
members of some minority groups—experience greater chronic stress. However, findings to date linking telomere length to specific aspects of social
status are mixed.

4

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Much of the research on social status and health, including telomere length,
has been done in the United Kingdom. Shorter white blood cell telomere
length was observed among British women in manual versus nonmanual
occupational classes and in unemployed versus employed Scottish men.
However, in these samples, telomere length was not associated with income
or education, or with neighborhood deprivation. In contrast, lower income
was associated with shorter telomere length in a study of Scottish men and
women, and two other studies in Britain found an association of shorter
telomere length with lower educational attainment, but not other indicators
of social disadvantage.
In the United States, studies have examined telomere length in relation to
race and ethnicity as well as to socioeconomic status. African-Americans are
exposed to greater chronic stress and have poorer health status than do other
groups. Within samples of African-Americans, the relationship between
psychological stress and short telomere length appears to hold. However,
African-Americans appear to have relatively longer telomeres than whites.
A recent study of older black and white adults demonstrated the importance
of considering the combination of race/ethnicity and socioeconomic status
in assessing telomere length. Although, overall, individuals with more than
a high school education had longer telomeres than those with a high school
education or less, this effect was moderated by race. There was relatively
little difference in telomere length by educational levels for whites, but a
marked difference for blacks. Indeed, the telomeres of blacks with more
than a high school education were not only significantly longer than those
of lesser-educated blacks but were also significantly longer than those of
whites no matter their level of education.
CUTTING-EDGE RESEARCH
MECHANISMS OF THE STRESS–TELOMERE RELATIONSHIP
The vast majority of studies linking the social environment with telomere
length focus on stress as a mediator of the association. Much research on
the health effects of chronic stress has focused on “allostatic load,” the
accumulated wear and tear on the body of repeated exposures to stress.
Allostatic load represents dysregulation of multiple systems within the body
and predicts future risk of morbidity and mortality. The same processes
that contribute to allostatic load are related to telomere shortening. Consequently, studies are currently making links between social disadvantage
and exposure to uncontrollable threatening situations on the one hand and
dysregulation of biological systems and accelerated cellular aging on the
other.

Telomeres

5

These studies reveal the biological effects of frequent cycles of threat and
disadvantage associated with lower social status. Social threats activate the
hypothalamic-pituitary-adrenal axis and increase production of cortisol and
proinflammatory proteins. These responses are functional in the short term
in preparing the body for “fight or flight” as well as for injury and infection. However, repeated and prolonged activation of these responses in the
socially disadvantaged can promote chronic biological changes that accelerate telomere shortening.
In addition to direct physiological effects of repeated and prolonged
activation of biological stress systems on telomeres, recent studies reveal an
indirect path from social status to cell aging through behavioral responses
individuals use to cope with stressful circumstances. Individuals with
fewer socioeconomic resources encounter more uncontrollable stressors
than do the more advantaged. Animal models have shown that exposure
to uncontrollable stress promotes greater ingestion of foods containing
fats and sugars. As with the stress response, this behavioral response
is functional because consuming such foods can downregulate cortisol
release. Among humans, stress-inducing exposures may not only elicit the
ingestion of energy dense “comfort foods” but also use of tobacco and
other substances. These bring short-term emotional relief and can dampen
down the stress response, but over time, can damage telomeres and the
body.
Individuals who have encountered repeated exposures to threatening and
uncontrollable situations may become more vigilant for information that
may signal potential threats. Such vigilance is advantageous in dangerous
environments. However, sensitivity to threat can be costly, leading to more
frequent and prolonged activation of biological stress systems even when
threats are absent or mild. When adolescents from different socioeconomic
backgrounds were asked to interpret videos of various kinds of social situations they made similar interpretations of clearly positive or clearly negative
scenarios. However, adolescents from families of lower socioeconomic
status interpreted ambiguous situations as more threatening than did their
more advantaged peers. Adolescents making more negative attributions to
ambiguous videos appeared to pay a price for their vigilance, exhibiting
higher blood pressure in overnight monitoring.
Biological stress responses to anticipated and actual threat—both of which
may be more common in socially disadvantaged individuals—may promote
telomere shortening. This pathway would explain recent finding that
women who rated a standardized acute laboratory stressor as more threatening had significantly shorter telomeres than those making more benign
appraisals.

6

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Buffers of the Stress–Telomere Relationship. Although stress appears to accelerate telomere shortening, individuals who are experiencing chronic stress may
be able to lessen its impact on their telomeres through engagement in healthy
behaviors. For example, physical activity may slow telomere attrition, especially in the face of stress. In one study, women who were physically active
showed no relationship between their reported levels of stress and the length
of their telomeres, while among those who did not exercise, those reporting
greater stress had significantly shorter telomeres.
Emerging evidence indicates that a lifestyle including physical activity,
good sleep and a diet enriched with fresh fruit and vegetables and lower
processed meat intake may slow telomere attrition. An important next
step will be translating findings into effective interventions. This will be
challenging. It is difficult to get people to maintain a healthy lifestyle, and
even more so when people are enduring high stress that requires attention
to immediate survival goals and emotional needs. Moreover, individuals
who are from socially disadvantaged groups have more limited access to
resources for engaging in health-promoting behaviors.
KEY ISSUES FOR FUTURE RESEARCH
TELOMERE LENGTHENING
One of the most exciting but also puzzling stories to have emerged in the
telomere field in recent years is the finding that telomeres may lengthen as
well as shorten. Although telomeres are longest at birth and shortest in old
age, accumulating evidence suggests that some individuals show telomere
lengthening over periods ranging from 1 to 5 years. The enzyme telomerase,
a reverse transcriptase that builds telomeric DNA and lengthens telomeres, may be responsible for this occurrence. In cells cultured in the laboratory, telomeres shorten with each cycle of cell division until they reach a
critical shortness called the Hayflick limit. At this critical point, cells become
functionally impaired and are unable to divide and produce daughter
cells. However, when telomerase is added to such cultures, telomeres are
maintained for longer, allowing the cells to continue dividing. This process
is tightly regulated to allow for damaged and older cells to die and leave the
system. The exception is found in cancer cells, which have short telomeres,
but can become immortal by expressing very high levels of telomerase.
Thus, at the same time that telomerase is beneficial in allowing healthy cells
to stay functional and proliferate, it can also be problematic by promoting
thriving in cancer cells.
In general, however, higher levels of telomerase are associated with better health in humans, suggesting that increased telomerase is advantageous

Telomeres

7

overall. For example, when prostate cancer patients engaged in comprehensive lifestyle improvements, their levels of telomerase increased. Physical
activity also activates telomerase and there are recent reports that mindfulness meditation interventions increase telomerase. Future studies are needed
to understand the factors that promote telomerase activity, and to elucidate
its ability to slow biological aging.
TELOMERE LENGTH MEASUREMENT
Telomere length is generally assessed from white blood cells using either
the “Southern blot” or the “quantitative real-time polymerase chain reaction” (Q-PCR) approach. Southern blot was the first method established for
telomere length measurement and subsequent developments have increased
its sensitivity. It serves as the “gold standard” for calibrating new methods,
but it is costly and labor intensive and requires a large amount of DNA. In
contrast, the Q-PCR approach and monochrome multiplex Q-PCR methods
require less DNA and lend themselves to the high throughput needed for
large studies.
More recent and more controversial is the use of buccal cells rather than
blood to assess telomere length. Buccal cells, obtained through cheek swabs,
are easier to obtain and may be more acceptable, especially in work with
children, than is collecting blood. Advances in telomere measurement from
dried blood spots also have the potential to reduce the burden of collecting
blood samples, especially in nonclinical settings.
Recent studies show that telomere length varies even within cells, and suggest that the shortest telomere within a cell may play a particularly important
role in influencing cell responses. Thus, newer approaches to telomere length
measurement that allow the measurement of individual telomeres and the
quantification of short telomeres within cells are likely to yield important
new insights.
PUBLIC HEALTH IMPLICATIONS
Research linking social disadvantage with telomere length provides a strong
foundation for designing interventions to improve health and diminish disparities, but much remains to be done before the findings can be translated
into real-world applications. We do not yet know how and when to intervene
to slow down cellular aging. While biological researchers seek ways to target the telomere maintenance system directly, social and behavioral scientists
may find ways to slow telomere shortening by improving social conditions
and/or psychological and behavioral responses to disadvantage. Such interventions need to be informed by knowledge of modifiable mechanisms of

8

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

telomere shortening, the conditions that foster these mechanisms and the
policies that can affect these conditions.
Greater understanding of the dynamics of telomere shortening over the
life course can inform the timing and targets of interventions. Most research
on telomeres has been in older people because diseases of aging linked to
telomere shortening occur in this population. However, strategies that affect
early-life determinants of telomere length may have a greater payoff. The
length of a person’s telomeres in older adulthood is a function of the length
of the telomeres with which they were endowed at conception as well as by
environmental exposures from the womb onward. Investment in enhancing
the early-life environment may hold much promise in changing trajectories
and promoting longevity and better health into old age.
FURTHER READING
Adler, N. E., & Stewart, J. (2010). Health disparities across the lifespan: Meaning,
methods, and mechanisms. Annals of the New York Academy of Sciences, 1186, 5–23.
Adler, N., Pantell, M., O’Donovan, A., Blackburn, E. H., Cawthon, R., Koster, A.,
… , Epel, E. (2013). Educational attainment and late life telomere length in the
health, aging and body composition study. Brain, Behavior, and Immunity, 27, 15–21.
10.1016/j.bbi.2012.08.014
Aubert, G., Hills, M., & Lansdorp, P. M. (2012). Telomere length measurementCaveats and a critical assessment of the available technologies and tools. Mutation
Research, 730, 59–67.
Entringer, S., Epel, E. S., Kumsta, R., Lin, J., Hellhammer, D. H., Blackburn, E. H., … ,
Wadhwa, P. D. (2011). Stress exposure in intrauterine life is associated with shorter
telomere length in young adulthood. Proceedings of the National Academy of Sciences
of the United States of America, 108(33), E513–518.
Epel, E. S., Blackburn, E. H., Lin, J., Dhabhar, F. S., Adler, N. E., Morrow, J. D., &
Cawthon, R. M. (2004). Accelerated telomere shortening in response to life stress.
Proceedings of the National Academy of Sciences of the United States of America, 101(49),
17312–17315.
Puterman, E., Lin, J., Blackburn, E., O’Donovan, A., Adler, N., & Elissa, E. (2010). The
power of exercise: Buffering the effect of chronic stress on telomere length. PLoS
ONE, 5(5), e10837. doi:10.1371/journal.pone.0010837
Shalev, I. (2012). Early life stress and telomere length: Investigating the connection
and possible mechanisms: A critical survey of the evidence base, research methodology and basic biology. Bioessays, 34, 943–952.

NANCY ADLER SHORT BIOGRAPHY
Nancy Adler, PhD is Lisa and John Pritzker Professor of Psychology in the
Departments of Psychiatry and Pediatrics, Vice-Chair of the Department of

Telomeres

9

Psychiatry, and Director of the Center for Health and Community at the University of California, San Francisco. A social psychologist, her early research
examined the utility of decision models for understanding health behaviors
with particular focus on reproductive health. Subsequently, she directed the
MacArthur Foundation Research Network on SES and Health in which an
interdisciplinary group of researchers identified and tested possible mechanisms by which socioeconomic status gets into the body to affect health.
In addition to documenting effects of objective socioeconomic status, she
demonstrated the importance of subjective social status. A special issue of
the Annals of the New York Academy of Sciences on the Biology of Disadvantage provides an overview of this work. While continuing to conduct
empirical research on social determinants of health, she has become increasingly interested in methodological challenges in assessing the relationship
of social disadvantage and health and in policy and interventions that could
affect these processes.
AOIFE O’DONOVAN SHORT BIOGRAPHY
Aoife O’Donovan, PhD is a Society in Science—Branco Weiss Fellow and
Assistant Professor in the Department of Psychiatry at the University of
California, San Francisco, and the San Francisco Veterans Affairs Medical
Center. She received her undergraduate education in psychology and philosophy at University College Cork and subsequently completed a Masters
in Health Psychology at the National University of Ireland, Galway. During
her Masters, she conducted experimental research examining the effects
of subtle manipulations of social support on cardiovascular responses to
acute stress. Following this, she pursued a PhD in Clinical Psychobiology
at University College Dublin focused on uncovering associations between
threat-related psychological variables and indices and mechanisms of
biological aging. Dr. O’Donovan’s laboratory is focused on uncovering
how chronic and traumatic stress exposure increase risk for psychiatric
and physical disorders, by studying both the psychological and biological
consequences of stress. The ultimate goal of this work is to inform the
development of new interventions that reduce the negative effects of
psychological stress on health.
RELATED ESSAYS
Social Epigenetics: Incorporating Epigenetic Effects as Social Cause and
Consequence (Sociology), Douglas L. Anderton and Kathleen F. Arcaro
Inefficiencies in Health Care Provision (Economics), James F. Burgess et al.
Self-Fulfilling Prophesies, Placebo Effects, and the Social-Psychological
Creation of Reality (Sociology), Alia Crum and Damon J. Phillips

10

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Genetic and Environmental Approaches to Political Science (Political Science),
Zoltán Fazekas and Peter K. Hatemi
Evolutionary Approaches to Understanding Children’s Academic Achievement (Psychology), David C. Geary and Daniel B. Berch
Genetics and Social Behavior (Anthropology), Henry Harpending and Gregory Cochran
An Evolutionary Perspective on Developmental Plasticity (Psychology),
Sarah Hartman and Jay Belsky
Niche Construction: Implications for Human Sciences (Anthropology), Kevin
N. Laland and Michael O’Brien
Immigrant Health Paradox (Sociology), Kyriakos S. Markides and Sunshine
Rote
Rationing of Health Care (Sociology), David Mechanic
Health and Social Inequality (Sociology), Bernice A. Pescosolido
Social Relationships and Health in Older Adulthood (Psychology), Theodore
F. Robles and Josephine A. Menkin
The Role of Cultural, Social, and Psychological Factors in Disease and Illness
(Sociology), Robert A. Scott
Incarceration and Health (Sociology), Christopher Wildeman


Telomeres
NANCY ADLER and AOIFE O’DONOVAN

Abstract
Telomeres cap the ends of chromosomes in the cell and their length provides a marker
of cellular aging. As people age, their telomeres generally shorten, a process that
is accelerated by exposure to chronic stress as well as by health behaviors such as
smoking, lack of exercise, and poor diet. Individuals who are lower on the social hierarchy have shorter telomeres on average, providing evidence of the health-damaging
effects of social disadvantage.

INTRODUCTION
Biomarkers alert patients and providers to incipient disease to allow early
intervention and monitor the efficacy of treatment. For example, elevated levels of glycated hemoglobin (HbA1c), reflecting the concentration of glucose
in the blood, signals increased risk of diabetes and may trigger attempts to
reduce risk through diet, exercise, and weight loss. If diabetes occurs, HbA1c
levels help monitor whether health behaviors and/or pharmaceutical treatments are effective in controlling the disorder. Biomarkers also provide information on the health of populations and enable us to link social factors to
internal biological process that can affect health.
Biomarkers are frequently used to assess stress responses and assess the
extent to which social circumstances trigger and modify these responses.
Most commonly used is cortisol, a hormone that mobilizes resources to allow
the body to activate “fight or flight” responses to deal with an immediate
threat. Cortisol levels have been linked to a range of social factors including low social rank in nonhuman primates, negative social evaluations in
laboratory settings, and low income. However, cortisol is more useful as a
measure of acute stress than of chronic stress and researchers have sought a
more stable biomarker that can better inform us about cumulative lifespan
effects.

Emerging Trends in the Social and Behavioral Sciences. Edited by Robert Scott and Stephen Kosslyn.
© 2015 John Wiley & Sons, Inc. ISBN 978-1-118-90077-2.

1

2

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

In this context, telomere length, a biomarker for cellular aging, has emerged
as a highly promising candidate. Unlike biomarkers that capture byproducts
of biological responses in specific systems, telomere length in white blood
cells may capture cumulative processes at the cellular and molecular level
throughout the body. White blood cells comprise various types of immune
cells that circulate in the system and serve important immune system
functions across bodily systems and tissues. Although it has not been
unequivocally shown that telomere attrition is a mechanism by which social
disadvantage leads to earlier development of chronic age-related diseases
and higher rates of mortality, white blood cell telomere length has been
linked both to experiences of chronic stress and disadvantage, and to
increased risk for specific diseases and mortality. We focus primarily on
disadvantage resulting from low socioeconomic status as reflected in low
income and education.
FOUNDATIONAL RESEARCH
TELOMERES
Telomeres are DNA–protein complexes that form protective caps on the ends
of chromosomes. Analogous to how the cap on the end of a shoelace protects
it from unraveling and fraying, the telomere on the tip of the chromosome
protects against damage to the DNA that encodes our genes. Over time, as
cells divide and are subject to biochemical stress, telomeres shorten. When
their length falls below a certain critical threshold, cells can become functionally impaired and unable to divide, and can undergo apoptosis or cell
death. Telomere length has been described as a “molecular clock” and the
shortening of telomeres with age is thought to play a mechanistic role in
age-related functional decline and increased risk for disease.
The number of studies of telomeres in humans has grown since the dawn
of the 21st Century. Such research has been facilitated by the fact that
telomeres in white blood cells can be easily measured in blood samples.
Although we do not yet know how strongly correlated telomeres from
white blood cells are with telomeres from other cell types, white blood
cell telomere length has emerged as a powerful biomarker. Prospective
studies have shown that individuals with shorter white blood cell telomeres
are more likely to develop age-related diseases such as cardiovascular
disease (including myocardial infarction and stroke), some types of cancer,
autoimmune disorders, and dementia.
The precise causes of telomere shortening in humans are not fully understood. However, there is evidence that telomere shortening is accelerated by
oxidative stress, the imbalance between oxidizing molecules and antioxidant

Telomeres

3

defenses, and by chronic activation of the inflammatory response of the
immune system. There is also some evidence that high levels of the stress
hormone cortisol may downregulate processes that maintain telomeres.
Oxidative stress and chronic inflammation, which are linked to greater
telomere attrition, are elevated among individuals who smoke, are physically
inactive and/or have high body mass index. Because socially disadvantaged
groups show higher rates of all these risk factors, they may be a pathway
by which social factors get into the body to affect health and longevity. In
addition, socially disadvantaged individuals experience greater chronic
psychological stress, which can also increase inflammation and oxidative
stress, may accelerate telomere attrition.
Stress and Telomere Length. Accumulating evidence links psychological stress
exposure with short telomere length. A groundbreaking study found shorter
telomeres among women experiencing greater distress as a result of caring
for a chronically ill child, and the longer the duration of the caregiving, the
shorter her telomeres. Subsequent studies have linked shorter telomeres to
other chronic stresses across the lifespan. One study found shorter telomeres
in the adult offspring of women who were exposed to stress during pregnancy. Another found a faster rate of telomere shortening from age 5 to age
10 among children exposed to maternal domestic violence, physical maltreatment and frequent bullying than among children without such exposure to
violence.
It is not simply exposure to threatening or stressful conditions that
leads to accelerated telomere attrition, but the individual’s appraisal and
cognitive-emotional response to the situation. For example, among the
mothers caring for a chronically ill child in the study described, shorter
telomeres were found primarily among those who experienced higher
levels of perceived psychological stress and comparison group mothers who
reported relatively high levels of perceived stress. Perceived psychological
stress appears, in fact, to be more robustly related to short telomere length
than is objective stress exposure. This stands to reason because stress gets
“under the skin” only to the extent that it activates the biological stress
response, which in turn is dependent on stress perception.
Social Determinants. Studies linking stress and telomere length suggest a possible pathway by which social disadvantage results in disease. Socially disadvantaged individuals—those with less education and lower incomes and
members of some minority groups—experience greater chronic stress. However, findings to date linking telomere length to specific aspects of social
status are mixed.

4

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Much of the research on social status and health, including telomere length,
has been done in the United Kingdom. Shorter white blood cell telomere
length was observed among British women in manual versus nonmanual
occupational classes and in unemployed versus employed Scottish men.
However, in these samples, telomere length was not associated with income
or education, or with neighborhood deprivation. In contrast, lower income
was associated with shorter telomere length in a study of Scottish men and
women, and two other studies in Britain found an association of shorter
telomere length with lower educational attainment, but not other indicators
of social disadvantage.
In the United States, studies have examined telomere length in relation to
race and ethnicity as well as to socioeconomic status. African-Americans are
exposed to greater chronic stress and have poorer health status than do other
groups. Within samples of African-Americans, the relationship between
psychological stress and short telomere length appears to hold. However,
African-Americans appear to have relatively longer telomeres than whites.
A recent study of older black and white adults demonstrated the importance
of considering the combination of race/ethnicity and socioeconomic status
in assessing telomere length. Although, overall, individuals with more than
a high school education had longer telomeres than those with a high school
education or less, this effect was moderated by race. There was relatively
little difference in telomere length by educational levels for whites, but a
marked difference for blacks. Indeed, the telomeres of blacks with more
than a high school education were not only significantly longer than those
of lesser-educated blacks but were also significantly longer than those of
whites no matter their level of education.
CUTTING-EDGE RESEARCH
MECHANISMS OF THE STRESS–TELOMERE RELATIONSHIP
The vast majority of studies linking the social environment with telomere
length focus on stress as a mediator of the association. Much research on
the health effects of chronic stress has focused on “allostatic load,” the
accumulated wear and tear on the body of repeated exposures to stress.
Allostatic load represents dysregulation of multiple systems within the body
and predicts future risk of morbidity and mortality. The same processes
that contribute to allostatic load are related to telomere shortening. Consequently, studies are currently making links between social disadvantage
and exposure to uncontrollable threatening situations on the one hand and
dysregulation of biological systems and accelerated cellular aging on the
other.

Telomeres

5

These studies reveal the biological effects of frequent cycles of threat and
disadvantage associated with lower social status. Social threats activate the
hypothalamic-pituitary-adrenal axis and increase production of cortisol and
proinflammatory proteins. These responses are functional in the short term
in preparing the body for “fight or flight” as well as for injury and infection. However, repeated and prolonged activation of these responses in the
socially disadvantaged can promote chronic biological changes that accelerate telomere shortening.
In addition to direct physiological effects of repeated and prolonged
activation of biological stress systems on telomeres, recent studies reveal an
indirect path from social status to cell aging through behavioral responses
individuals use to cope with stressful circumstances. Individuals with
fewer socioeconomic resources encounter more uncontrollable stressors
than do the more advantaged. Animal models have shown that exposure
to uncontrollable stress promotes greater ingestion of foods containing
fats and sugars. As with the stress response, this behavioral response
is functional because consuming such foods can downregulate cortisol
release. Among humans, stress-inducing exposures may not only elicit the
ingestion of energy dense “comfort foods” but also use of tobacco and
other substances. These bring short-term emotional relief and can dampen
down the stress response, but over time, can damage telomeres and the
body.
Individuals who have encountered repeated exposures to threatening and
uncontrollable situations may become more vigilant for information that
may signal potential threats. Such vigilance is advantageous in dangerous
environments. However, sensitivity to threat can be costly, leading to more
frequent and prolonged activation of biological stress systems even when
threats are absent or mild. When adolescents from different socioeconomic
backgrounds were asked to interpret videos of various kinds of social situations they made similar interpretations of clearly positive or clearly negative
scenarios. However, adolescents from families of lower socioeconomic
status interpreted ambiguous situations as more threatening than did their
more advantaged peers. Adolescents making more negative attributions to
ambiguous videos appeared to pay a price for their vigilance, exhibiting
higher blood pressure in overnight monitoring.
Biological stress responses to anticipated and actual threat—both of which
may be more common in socially disadvantaged individuals—may promote
telomere shortening. This pathway would explain recent finding that
women who rated a standardized acute laboratory stressor as more threatening had significantly shorter telomeres than those making more benign
appraisals.

6

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Buffers of the Stress–Telomere Relationship. Although stress appears to accelerate telomere shortening, individuals who are experiencing chronic stress may
be able to lessen its impact on their telomeres through engagement in healthy
behaviors. For example, physical activity may slow telomere attrition, especially in the face of stress. In one study, women who were physically active
showed no relationship between their reported levels of stress and the length
of their telomeres, while among those who did not exercise, those reporting
greater stress had significantly shorter telomeres.
Emerging evidence indicates that a lifestyle including physical activity,
good sleep and a diet enriched with fresh fruit and vegetables and lower
processed meat intake may slow telomere attrition. An important next
step will be translating findings into effective interventions. This will be
challenging. It is difficult to get people to maintain a healthy lifestyle, and
even more so when people are enduring high stress that requires attention
to immediate survival goals and emotional needs. Moreover, individuals
who are from socially disadvantaged groups have more limited access to
resources for engaging in health-promoting behaviors.
KEY ISSUES FOR FUTURE RESEARCH
TELOMERE LENGTHENING
One of the most exciting but also puzzling stories to have emerged in the
telomere field in recent years is the finding that telomeres may lengthen as
well as shorten. Although telomeres are longest at birth and shortest in old
age, accumulating evidence suggests that some individuals show telomere
lengthening over periods ranging from 1 to 5 years. The enzyme telomerase,
a reverse transcriptase that builds telomeric DNA and lengthens telomeres, may be responsible for this occurrence. In cells cultured in the laboratory, telomeres shorten with each cycle of cell division until they reach a
critical shortness called the Hayflick limit. At this critical point, cells become
functionally impaired and are unable to divide and produce daughter
cells. However, when telomerase is added to such cultures, telomeres are
maintained for longer, allowing the cells to continue dividing. This process
is tightly regulated to allow for damaged and older cells to die and leave the
system. The exception is found in cancer cells, which have short telomeres,
but can become immortal by expressing very high levels of telomerase.
Thus, at the same time that telomerase is beneficial in allowing healthy cells
to stay functional and proliferate, it can also be problematic by promoting
thriving in cancer cells.
In general, however, higher levels of telomerase are associated with better health in humans, suggesting that increased telomerase is advantageous

Telomeres

7

overall. For example, when prostate cancer patients engaged in comprehensive lifestyle improvements, their levels of telomerase increased. Physical
activity also activates telomerase and there are recent reports that mindfulness meditation interventions increase telomerase. Future studies are needed
to understand the factors that promote telomerase activity, and to elucidate
its ability to slow biological aging.
TELOMERE LENGTH MEASUREMENT
Telomere length is generally assessed from white blood cells using either
the “Southern blot” or the “quantitative real-time polymerase chain reaction” (Q-PCR) approach. Southern blot was the first method established for
telomere length measurement and subsequent developments have increased
its sensitivity. It serves as the “gold standard” for calibrating new methods,
but it is costly and labor intensive and requires a large amount of DNA. In
contrast, the Q-PCR approach and monochrome multiplex Q-PCR methods
require less DNA and lend themselves to the high throughput needed for
large studies.
More recent and more controversial is the use of buccal cells rather than
blood to assess telomere length. Buccal cells, obtained through cheek swabs,
are easier to obtain and may be more acceptable, especially in work with
children, than is collecting blood. Advances in telomere measurement from
dried blood spots also have the potential to reduce the burden of collecting
blood samples, especially in nonclinical settings.
Recent studies show that telomere length varies even within cells, and suggest that the shortest telomere within a cell may play a particularly important
role in influencing cell responses. Thus, newer approaches to telomere length
measurement that allow the measurement of individual telomeres and the
quantification of short telomeres within cells are likely to yield important
new insights.
PUBLIC HEALTH IMPLICATIONS
Research linking social disadvantage with telomere length provides a strong
foundation for designing interventions to improve health and diminish disparities, but much remains to be done before the findings can be translated
into real-world applications. We do not yet know how and when to intervene
to slow down cellular aging. While biological researchers seek ways to target the telomere maintenance system directly, social and behavioral scientists
may find ways to slow telomere shortening by improving social conditions
and/or psychological and behavioral responses to disadvantage. Such interventions need to be informed by knowledge of modifiable mechanisms of

8

EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

telomere shortening, the conditions that foster these mechanisms and the
policies that can affect these conditions.
Greater understanding of the dynamics of telomere shortening over the
life course can inform the timing and targets of interventions. Most research
on telomeres has been in older people because diseases of aging linked to
telomere shortening occur in this population. However, strategies that affect
early-life determinants of telomere length may have a greater payoff. The
length of a person’s telomeres in older adulthood is a function of the length
of the telomeres with which they were endowed at conception as well as by
environmental exposures from the womb onward. Investment in enhancing
the early-life environment may hold much promise in changing trajectories
and promoting longevity and better health into old age.
FURTHER READING
Adler, N. E., & Stewart, J. (2010). Health disparities across the lifespan: Meaning,
methods, and mechanisms. Annals of the New York Academy of Sciences, 1186, 5–23.
Adler, N., Pantell, M., O’Donovan, A., Blackburn, E. H., Cawthon, R., Koster, A.,
… , Epel, E. (2013). Educational attainment and late life telomere length in the
health, aging and body composition study. Brain, Behavior, and Immunity, 27, 15–21.
10.1016/j.bbi.2012.08.014
Aubert, G., Hills, M., & Lansdorp, P. M. (2012). Telomere length measurementCaveats and a critical assessment of the available technologies and tools. Mutation
Research, 730, 59–67.
Entringer, S., Epel, E. S., Kumsta, R., Lin, J., Hellhammer, D. H., Blackburn, E. H., … ,
Wadhwa, P. D. (2011). Stress exposure in intrauterine life is associated with shorter
telomere length in young adulthood. Proceedings of the National Academy of Sciences
of the United States of America, 108(33), E513–518.
Epel, E. S., Blackburn, E. H., Lin, J., Dhabhar, F. S., Adler, N. E., Morrow, J. D., &
Cawthon, R. M. (2004). Accelerated telomere shortening in response to life stress.
Proceedings of the National Academy of Sciences of the United States of America, 101(49),
17312–17315.
Puterman, E., Lin, J., Blackburn, E., O’Donovan, A., Adler, N., & Elissa, E. (2010). The
power of exercise: Buffering the effect of chronic stress on telomere length. PLoS
ONE, 5(5), e10837. doi:10.1371/journal.pone.0010837
Shalev, I. (2012). Early life stress and telomere length: Investigating the connection
and possible mechanisms: A critical survey of the evidence base, research methodology and basic biology. Bioessays, 34, 943–952.

NANCY ADLER SHORT BIOGRAPHY
Nancy Adler, PhD is Lisa and John Pritzker Professor of Psychology in the
Departments of Psychiatry and Pediatrics, Vice-Chair of the Department of

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Psychiatry, and Director of the Center for Health and Community at the University of California, San Francisco. A social psychologist, her early research
examined the utility of decision models for understanding health behaviors
with particular focus on reproductive health. Subsequently, she directed the
MacArthur Foundation Research Network on SES and Health in which an
interdisciplinary group of researchers identified and tested possible mechanisms by which socioeconomic status gets into the body to affect health.
In addition to documenting effects of objective socioeconomic status, she
demonstrated the importance of subjective social status. A special issue of
the Annals of the New York Academy of Sciences on the Biology of Disadvantage provides an overview of this work. While continuing to conduct
empirical research on social determinants of health, she has become increasingly interested in methodological challenges in assessing the relationship
of social disadvantage and health and in policy and interventions that could
affect these processes.
AOIFE O’DONOVAN SHORT BIOGRAPHY
Aoife O’Donovan, PhD is a Society in Science—Branco Weiss Fellow and
Assistant Professor in the Department of Psychiatry at the University of
California, San Francisco, and the San Francisco Veterans Affairs Medical
Center. She received her undergraduate education in psychology and philosophy at University College Cork and subsequently completed a Masters
in Health Psychology at the National University of Ireland, Galway. During
her Masters, she conducted experimental research examining the effects
of subtle manipulations of social support on cardiovascular responses to
acute stress. Following this, she pursued a PhD in Clinical Psychobiology
at University College Dublin focused on uncovering associations between
threat-related psychological variables and indices and mechanisms of
biological aging. Dr. O’Donovan’s laboratory is focused on uncovering
how chronic and traumatic stress exposure increase risk for psychiatric
and physical disorders, by studying both the psychological and biological
consequences of stress. The ultimate goal of this work is to inform the
development of new interventions that reduce the negative effects of
psychological stress on health.
RELATED ESSAYS
Social Epigenetics: Incorporating Epigenetic Effects as Social Cause and
Consequence (Sociology), Douglas L. Anderton and Kathleen F. Arcaro
Inefficiencies in Health Care Provision (Economics), James F. Burgess et al.
Self-Fulfilling Prophesies, Placebo Effects, and the Social-Psychological
Creation of Reality (Sociology), Alia Crum and Damon J. Phillips

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EMERGING TRENDS IN THE SOCIAL AND BEHAVIORAL SCIENCES

Genetic and Environmental Approaches to Political Science (Political Science),
Zoltán Fazekas and Peter K. Hatemi
Evolutionary Approaches to Understanding Children’s Academic Achievement (Psychology), David C. Geary and Daniel B. Berch
Genetics and Social Behavior (Anthropology), Henry Harpending and Gregory Cochran
An Evolutionary Perspective on Developmental Plasticity (Psychology),
Sarah Hartman and Jay Belsky
Niche Construction: Implications for Human Sciences (Anthropology), Kevin
N. Laland and Michael O’Brien
Immigrant Health Paradox (Sociology), Kyriakos S. Markides and Sunshine
Rote
Rationing of Health Care (Sociology), David Mechanic
Health and Social Inequality (Sociology), Bernice A. Pescosolido
Social Relationships and Health in Older Adulthood (Psychology), Theodore
F. Robles and Josephine A. Menkin
The Role of Cultural, Social, and Psychological Factors in Disease and Illness
(Sociology), Robert A. Scott
Incarceration and Health (Sociology), Christopher Wildeman



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