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Elizabeth Crown at (312) 503-8928 or e-mail at [email protected]
CHICAGO --- With a little more than spit and a sponge, researchers at Northwestern University Medical School can now test whether an individual is experiencing physical or emotional stress.
The test measures concentration of an enzyme, called amylase, in saliva. Research has shown that salivary amylase concentration reflects the body's level of catecholamines, substances produced by the sympathetic nervous system in response to stress.
According to Northwestern researcher Robert T. Chatterton, Jr., who directed the development of the test, the saliva amylase test may be a more direct and simple indicator of stress than are changes in heart rate. Chatterton is a professor of obstetrics and gynecology and of physiology at Northwestern University Medical School.
Other stress assessment methods require drawing blood or handling urine samples and must be performed in a laboratory. The saliva amylase test, which was developed and tested in collaboration with scientists at the U.S. Army Research Laboratory, Aberdeen Proving Ground, Md., is non-invasive and can be done on-site during potentially stressful or hazardous situations, such as military field maneuvers.
The test uses a small sponge inserted between the cheek and gums to absorb a sample of saliva, which is then collected in a disposable plastic beaker and mixed with a reagent, a substance that produces a chemical reaction, to detect amylase. In this test, the saliva-reagent mixture changes from clear to yellow over time; i.e., the faster the color change, the higher the amylase concentration and, therefore, the level of stress.
The best known catecholamines are dopamine, norepinephrine and epinephrine (also known as adrenaline). Epinephrine is commonly known as the "emergency hormone" because it is released during emotional stress, and its stimulatory effects fortify and prepare an animal for either "fight or flight." Concentrations of norepinephrine and epinephrine tend to increase in parallel, speeding up the rate and force of contraction of the heart and increasing both blood output from the heart as well as blood pressure.
In the group's early experiments, volunteer subjects were tested in physically and/or psychologically stressful situations, including skydiving and taking college final examinations. The investigators showed that blood levels of norepinephrine associated with the stress responses could be estimated by the concentrations of amylase in saliva specimens.
The Army Research Laboratory already is using the saliva amylase stress test in military units involved in clean-up of hazardous materials.
In addition, researchers at Northwestern University Medical School and at the School of Nursing at the University of Illinois, Chicago, will use the test to assess stress levels in mothers of premature infants. These women frequently experience difficulty nursing their babies because the catecholamine stress response may interfere with milk let-down and, eventually, lactation.
Chatterton said that the test may prove a valuable non-invasive addition to methods used in hospital emergency rooms to evaluate patients suspected of having a heart attack. The test also could be used to monitor stress levels in patients after a heart attack, he said.
Collaborating on the development of the test were Yu-cai Lu, Kirsten M. Vogelsong and Allison B. Ellman at Northwestern and Linda Fatkin and Gerald A. Hudgens at the U.S. Army Research Laboratory, Aberdeen Proving Ground, Md. (Editor's note: Dr. Chatterton can be reached at (312) 908-1569.)
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