| Research Statement
While it is fashionable to claim
that the nature-nurture controversy has been laid to rest, or to point
to the fallacy of mind-body dualism, rarely does current research embody
these ideals. Lacking are conceptual and methodological tools for
integrative, multi-level research on human biology and health in relation
to dynamic social, cultural, and physical ecologies. I have devoted
considerable effort to developing these tools in order to advance theoretically
driven, methodologically grounded research on the biocultural ecology of
human health.
Three common threads weave their
way through my work. The first emphasizes the importance of understanding
human biology in relation to the surrounding cultural ecological contexts
that shape its character. This is particularly the case for the immune
system—a system that is designed (in an evolutionary sense) to incorporate
information from the environment to guide its development.
The second involves a primary
focus on the life course more generally, and human development and the
experience of youth in particular. A developmental, life course approach
provides an opportunity to investigate the dynamic biological, cultural,
and psychosocial factors that shape trajectories of human development,
human biology, and human health at various stages of life.
Lastly, the application of innovative
biomarker methods amenable to the constraints of field-based research is
a third major theme. These methods are central to each of my projects,
and expand the range of questions that I can address. In addition,
they have challenged me to deal with important interpretive and conceptual
issues as I attempt to study immune function and health in non-clinical,
community-based settings.
My research efforts thus far
can be divided into three primary areas, each of which is discussed here
in more detail, with links to relevant publications. While they are
presented as separate areas, I see them as tightly linked, converging areas
of research that inform an integrative, biocultural approach to human biology
and health.
Integrative, biocultural
perspectives on stress and health
The mental and physical health
consequences of rapid culture change have been topics of intense anthropological
interest, but previous research has been hampered by relatively limited
models of culture change (e.g., urban-rural comparisons), and challenges
associated with the physiological measurement of stress in remote field
settings. Outside of anthropology, the subdiscipline of psychoneuroimmunology—a
growing area of research in psychology and behavioral medicine that explores
the interconnections among the endocrine, nervous, and immune systems—has
demonstrated that psychosocial stress is an important modulator of immune
function. However, this research has been conducted exclusively among
western populations.
My research in Samoa attempts
to bring these perspectives together: methodological tools are borrowed
from psychoneuroimmunology to assess the immunological effects of psychosocial
stress, and anthropological models of culture change and stress are developed
to expand the current range of psychoneuroimmunological research.
Publications from this project have been significant in that they: 1) are
the first to introduce an anthropological perspective to research in stress
and immune function, and lay the foundation for future population-level
research in psychoneuroimmunology; 2) provide new models of culture change
that capture the individual-level person-environment dynamics associated
with stress for youth in Samoa (and possibly elsewhere); and 3) evaluate
and validate new “field-friendly” immunological methods for assessing chronic
stress that can be used in future research. Furthermore, I feel that
this work demonstrates the importance of integrating cultural and biological
methods and data, and highlights the value of biomarkers as ethnographic
tools as well as indicators of the physiological imprint of socio-cultural
contexts.
Recently I have made an explicit
effort to draw on the lessons of my work in Samoa to contribute a biocultural
anthropological perspective to U.S.-based research on socio-cultural environments,
stress, and health. I am collaborating with colleagues at the University
of Chicago on two studies of social relationships, aging and health—one
drawing on a national sample (National
Social Life, Health, and Aging Project), the other conducted locally
(The
Chicago Health, Aging, and Social Relations Study). At Northwestern
we have recently established a new interdisciplinary research center (Cells
to Society (C2S): Center on Social Disparities and Health) dedicated
to innovative, multi-level research on health that integrates concepts
and tools from the social, life, and biomedical sciences. With colleagues
at C2S I have recently submitted a RO1 proposal to investigate the health
impact of psychosocial stress in a large, nationally representative population
of young adults (National Longitudinal Study of Adolescent Health).
If funded, this study will be the most comprehensive analysis of stress
biomarkers to date, and will elucidate some of the pathways through which
social contexts “get under the skin” to shape our well-being.
Relevant articles*
McDade,
TW, Hawkley, LC and JT Cacioppo (2006). Psychosocial and behavioral
predictors of inflammation in middle-age and older adults: The Chicago
Health, Aging, and Social Relations Study.
Psychosomatic Medicine
68: 376-81.
Sweet, E., McDade, TW, Kiefe, C and K Liu (under review).
The interaction between skin color, income, and blood pressure among African
Americans in the CARDIA Study.
McDade,
TW and CM Worthman (2004). Socialization ambiguity in Samoan
adolescents: A new model for research in human development and stress
in the context of culture change. Journal of Research in Adolescence
14: 49-72.
McDade,
TW (2003). Life event stress and immune function in Samoan adolescents:
Toward a cross-cultural psychoneuroimmunology. In Social and Cultural
Lives of Immune Systems: Contextualizing Psychoneuroimmunology, Embodying
the Social Sciences, J. Wilce (ed.). New York: Routledge, pp.
170-188.
McDade,
TW (2002). Status incongruity in Samoan youth: A biocultural
analysis of culture change, stress, and immune function. Medical
Anthropology Quarterly 16: 123-150.
McDade,
TW (2001). Lifestyle incongruity, social integration, and immune
function in Samoan adolescents. Social Science and Medicine
53: 1351-1362.
McDade,
T.W., Stallings, J.F. and C.M. Worthman (2000). Culture change
and stress in Western Samoan youth: Methodological issues in the
cross-cultural study of stress and immune function. American Journal
of Human Biology 12: 792-802.
Human ecological
immunology and global health
Current biomedical research
on immune function focuses primarily on cellular and molecular mechanisms
of defense, but the human immune system is a product of natural selection
that develops and functions in whole organisms that are integral parts
of their surrounding environments. In addition, immune function provides
critical protection against infectious disease, and is a central mediator
of the bi-directional associations between infection and undernutrition.
A comparative, population-level, ecological perspective is therefore a
necessary complement to current biomedical research, and my work in Samoa
represents a first step in exploring the social ecology of stress and immunity
in a non-western setting. However, additional factors are important
determinants of immune development and function, and I have been working
toward a more comprehensive analysis of the developmental ecology of human
immunity through ongoing field research in the Philippines and Bolivia.
The Cebu
Longitudinal Health and Nutrition Survey (CLHNS) is an ongoing study
of maternal and child health in the Philippines, and I have been using
this dataset to evaluate the long-term effects of prenatal and early postnatal
environments on adolescent immunocompetence. By analyzing blood samples
from Filipino adolescents for 3 aspects of immune function (thymic hormone
levels, antibody response to typhoid vaccination, total IgE concentration),
and relating these results to data collected while these adolescents were
infants, we were able to show that the ecologies of nutrition and infectious
disease experienced in utero and in early infancy have long-term effects
on immune function. Publications from this work were the first to
document evidence of early “programming” of the immune system—a process
that may have significant implications for current understandings of adaptation
and human development.
Complementary research in lowland
Bolivia is exploring the ecology of immune function, infectious disease,
and child growth among the Tsimane’, a relatively isolated Amerindian population.
The Tsimane’ are at the earliest stages of cultural and economic transition,
and provide a unique opportunity to investigate the local implications
of globalization. In addition, they represent an interesting contrast
to my earlier work in Samoa, where engagement with western lifestyles had
been occurring for decades. Laboratory and data analyses are currently
ongoing, but preliminary work indicates that high burdens of infectious
disease (as measured by a biomarker of immune activation, C-reactive protein)
likely contribute to growth faltering among Tsimane’ children, and that
erosion of local ethnobotanical knowledge associated with acculturation
may undermine child health.
Through my research in Samoa,
the Philippines, and Bolivia I have attempted to demonstrate the importance
of population-based research on human immune development and function in
a wide range of cultural and ecological settings. Recent review articles
construct a foundation for this effort: My Yearbook paper draws on
life history theory to generate testable hypotheses regarding the tradeoffs
associated with investment in immunity versus other critical life history
functions involving growth and reproduction, and to propose an explanation
for the anomalous developmental trajectory of human immune tissues.
My Annual Review article builds on this analysis by attempting to integrate
physical as well as social factors shaping immune function for a more comprehensive
cultural ecological perspective on human immunity. Both these articles—as
well as earlier review papers on immune function and breastfeeding—reflect
my interest in developing theory-based conceptual models to guide future
research into the biocultural ecology of human health.
Relevant publications*
McDade, T.W.,
Leonard, W.R., Burhop, J., Reyes-García, V., Vadez, V., Huanca,
T. and R.A. Godoy (2005). Predictors of C-reactive protein in
Tsimane’ 2-15 year-olds in lowland Bolivia. American Journal of
Physical Anthropology.
McDade,
T.W. (2005). The ecologies of human immune function. Annual
Review of Anthropology.
McDade,
T.W. (2005). Life history, maintenance, and the early origins
of immune function. American Journal of Human Biology 17:
81-94.
McDade,
T.W., Kuzawa, C., Adair, L.S., and M. Beck (2004). Prenatal and
early postnatal environments are significant predictors of IgE concentration
in Filipino adolescents. Clinical and Experimental Allergy
34: 44-50.
McDade,
T.W. (2003). Life history theory and the immune system:
Steps toward a human ecological immunology. Yearbook of Physical
Anthropology 46: 100-125.
McDade,
T.W., Beck, M.A., Kuzawa, C. and L.S. Adair (2001). Prenatal
undernutrition, postnatal environments, and antibody response to vaccination
in adolescence. American Journal of Clinical Nutrition 74:
543-548.
McDade,
T.W., Beck, M.A., Kuzawa, C. and L.S. Adair (2001). Prenatal
undernutrition and postnatal growth are associated with adolescent thymic
function. Journal of Nutrition 131: 1225-1235.
McDade,
T.W. and C.M. Worthman (1999). Evolutionary process and the ecology
of human immune function. American Journal of Human Biology
11: 705-717.
McDade,
T.W. and C.M. Worthman (1998). The weanling’s dilemma reconsidered:
A biocultural analysis of breastfeeding ecology. Journal of Developmental
and Behavioral Pediatrics 19: 286-299.
Barrett, R.L., Kuzawa, C., McDade, T.W. and G.J. Armelagos
(1998). Emerging and re-emerging infectious diseases: The third
epidemiologic transition. Annual Review of Anthropology 27:
247-271.
Development of minimally-invasive
biomarker methods
Much research in biological
anthropology (as well as recent work in social epidemiology and biodemography)
attempts to link social/cultural and ecological contexts to variation in
growth and health outcomes through proximate physiological mechanisms.
Logistical constraints associated with the collection of biological samples
in field-based settings has proven to be a significant challenge to this
effort, and has limited the range of questions that can be addressed.
In an attempt to overcome some of these challenges, a major focus of my
work has been the development of minimally-invasive, “field-friendly” methods
for measuring biomarkers of human health and development. In particular,
I have focused on whole blood spots as a convenient means for collecting,
transporting, and processing blood samples from community settings.
In contrast to the relative invasiveness of venipuncture, whole blood samples
can be collected from a simple finger prick. Samples are dried on
filter paper, and—unlike plasma samples—do not need to be centrifuged or
immediately frozen.
To date, I have successfully
used this technique to collect blood samples from children and adolescents
in Samoa, Kenya, and Bolivia, and I have developed laboratory methods for
measuring aspects of immune function (antibodies against the Epstein-Barr
virus, C-reactive protein) and nutritional status (serum transferrin receptor,
leptin). These methods are currently being added to a number of national
health surveys, including the National Longitudinal Study of Adolescent
Health, and National Social Life, Health, and Aging Project, and the Health
and Retirement Study. These methods are significant in that they
facilitate the study of physiological mechanisms in the context of social
processes, promote future field-based research into the ecology of immune
function and health, and expand the range of questions that can be addressed
by human population biology.
We have developed the Laboratory
for Human Biology Research in the Anthropology Department as a facility
that will promote this type of innovation. The Lab comprises 1,500
square feet of Biosafety Level 2 certified wet-lab space, and is fully
equipped to perform a range of immunoassays on human blood and saliva.
In particular, the Lab possesses the latest generation of immunoassay technology—the
Luminex multi-analyte flow analyzer—that allows for the simultaneous analysis
of multiple factors in very small quantities of sample. Validation
of this technology for use with blood spot samples in currently underway.
Relevant publications*
McDade, T.W. (in press). Measuring immune function:
Markers of cell-mediated immunity and inflammation in dried blood spots.
In A Practical Guide to Measuring Stress in the Field, G.H. Ice
and G.D. James (eds.).
McDade,
T.W., Burhop, J., and J. Dohnal (2004). High sensitivity enzyme
immunoassay for C-reactive protein in dried blood spots. Clinical
Chemistry 50: 652-654.
Shell-Duncan,
B. and T.W. McDade (2004). Use of combined measures from capillary
blood to assess iron deficiency in rural Kenyan children. Journal
of Nutrition 134: 384-387.
McDade,
T.W. and B. Shell-Duncan (2002). Whole blood collected on filter
paper provides a minimally-invasive method for assessing human transferrin
receptor. Journal of Nutrition 132: 3760-3763.
McDade,
T.W., Stallings, J.F., Angold, A., Costello, E.J., Burleson, M., Cacioppo,
J.T., Glaser, R. and C.M. Worthman (2000). Epstein-Barr virus
antibodies in whole blood spots: A minimally-invasive method for
assessing an aspect of cell-mediated immunity. Psychosomatic Medicine
62: 560-568.
*Note: All articles are the sole copyright
of the respective publishers. Materials are provided for educational use
only.
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