Table 3.
Secondary Outcomes Related to Chronic Stress.
| Biomarker | Measurement | Overview of Biomarker Function |
|---|---|---|
| Neurologic | ||
| Hippocampal volume/activity | MRI and fMRI | Involved in learning and memory formation; also regulates negative feedback of glucocorticoids in HPA-axis response to stress |
| Amygdala volume/activity | MRI and fMRI | Involved in fear conditioning and emotional processing |
| Immune | ||
| C-reactive protein | Serum, saliva, and urine | Protein synthesized in the liver; stimulated by inflammatory cytokines and altered by glucocorticoid levels |
| Fibrinogen | Serum and urine | Glycoprotein produced by the liver; involved in platelet and erythrocyte aggregation, determines plasma viscosity |
| Secretory IgA | Serum, saliva, and urine | Antibody primarily produced in mucous membranes of the intestinal tract; protects epithelium from harmful toxins and microorganisms |
| Metabolic | ||
| Insulin | Serum, saliva, and urine | Hormone produced by the pancreas; involved in glucose metabolism |
| Glucose | Serum, saliva, and urine | Monosaccharide synthesized in the liver and kidneys; body’s main energy source |
| Leptin | Serum, saliva, and urine | Hormone secreted from adipose tissue; regulates energy homeostasis |
| α-Amylase | Serum, saliva, and urine | Enzyme produced by the salivary glands; initiates digestion of carbohydrates and starches. |
| Lipids | Serum, saliva | Lipoproteins (HDL and LDL) and triglycerides responsible for transport of cholesterol and dietary fat |
| Cardiovascular and respiratory | ||
| Blood pressure | Sphygmomanometer | Reflects force exerted by blood against the blood vessel walls during systole and diastole; elevated in SNS response to stress |
| Heart rate | Arterial pulsations | Number of palpations made by the heart within a specified period of time; elevated in SNS response to stress |
| Heart rate variability | Electrocardiogram | Variation in the time interval between palpations of the heart; reflects ANS activity |
| RSA | Electrocardiogram | Variation in heart rate that occurs during a respiratory cycle; indicator of cardiac vagal tone |
| Anthropometric | ||
| BMI | Height and weight | Measure of weight relative to height; estimation of body fat percentage based on age and gender-specific standards |
| Waist circumference | Waist circumference | Measure of distance around the abdomen; estimation of abdominal adiposity |
| Waist-to-hip ratio | Waist and hip circumferences | Measure of waist circumference divided by hip circumference; measure of central adiposity |
| Waist-to-height ratio | Waist circumference and height | Measure of waist circumference relative to height; estimates distribution of body fat |
| Growth and stature | Height | Measure of growth/stature relative to age and gender-specific standards |
Note. ANS = autonomic nervous system; BMI = body mass index; fMRA = functional magnetic resonance imaging; HDL = high-density lipoproteins; HPA = hypothalamic-pituitary-adrenal; IgA = immunoglobulin; LDL = low-density lipoproteins; MRI = magnetic resonance imaging; RSA = respiratory sinus arrhythmia; SNS = sympathetic nervous system.