Blood / Saliva Biomarkers
Numerous biomarkers of immune or endocrine function and nutritional status are measurable in saliva or dried blood spots. Biomarkers allow us to examine proximal physiological processes that bridge the gap between daily experience and health. We frequently evaluate and/or modify assay protocols to expand the range of analytes we can support, depending on the needs of particular research projects. Representative assays currently in use in the lab include, but are not limited to:
- Salivary and hair cortisol. Cortisol is the major peripheral end product of the hypothalamic-pituitary-adrenal axis and has a long history of use in biocultural or biosocial research as a "stress hormone" given the robust cortisol response to psychological distress. Beyond stress, cortisol is involved in arousal regulation quite broadly, and has widespread peripheral and central regulatory functions.
- Salivary α-amylase. A digestive enzyme found in human saliva, α-amylase has received recent attention as a marker of the autonomic response to acute psychosocial stress.
- C-reactive protein. CRP, an acute phase protein that can be detected in dried blood spots, serves as a marker of inflammation and infectious disease load. Chronically high CRP levels may be associated with elevated cardiovascular risk.
- Antibodies against ubiquitous herpesviruses. Antibodies against ubiquitous herpesviruses such as EBV and CMV can be detected in dried blood spots, and serve as markers of chronic stress and allostatic load.
- Soluble Transferrin Receptor. sTfR serves as a marker of iron deficiency and can help distinguish iron deficiency anemia from other causes of anemia.
- Glycated hemoglobin. HbA1c is a marker of glycemic (blood sugar) control, and can be measured in serum or using an instant point of care device.
- Immunoglobulin E. IgE antibodies are involved in the immune response to helminth parasites, and they also have an important role in allergic diseases. Tests of total IgE can be used to examine parasite load, and to test hypotheses regarding the development of allergies and asthma across ecological contexts.
The lab also includes the expertise to employ EKG, skin conductance and impedance cardiography for the non-invasive measurement of peripheral autonomic nervous system activity. Individual differences in ANS activity can be used to evaluate the differential impact of experience.
- Respiratory Sinus Arrhythmia. RSA (also known as high-frequency heart period variation) is a marker of vagal (parasympathetic) control over cardiac activity, and is a valuable measure in models linking physiological, social, and emotion regulation. RSA is assessed through spectral analysis of EKG.
- Pre-ejection Period. PEP, measured using impedance cardiography, is a marker of sympathetic control over cardiac activity. PEP and RSA often are measured together to evaluate simultaneously how the two branches of the autonomic nervous system respond to some stimulus.
- Galvanic skin response. GSR (skin conductance) is an alternative, non-cardiac marker of sympathetic activity.
The lab relies on detailed tracking of daily social experience for the social and cultural contextualization of physiology. We also track physical activity patterns throughout the day to determine how daily activity patterns translate into energy expenditure.
- Daily Life Architecture and PROUST. Using the DLA method, we are able to guide participants through the creation of detailed 24-hour diaries regarding daily activities, behaviors, and experience. DLA diaries are designed not only to record individual events and their frequency, but also to capture the sequencies and contingencies that link events. Equally important, DLA is an ethnographic tool used to identify cultural models as they are enacted in daily life. PROUST is the computer program for Personal Digital Assistants (PDAs) we and collaborators have created to implement the DLA experience tracking approach.
- Actigraphy. The lab uses small, non-invasive accelerometers worn around the waist or wrist to monitor the intensity of physical activity throughout the day. When combined with behavior/experience tracking through the DLA approach, and outcome measures such as body composition, actigraphy provides a powerful means to examine how culture and daily experience combine to influence human energetics.