Research shows that there are two distinct systems involved in the stress response of humans and other animals. The response and activity of both systems can be measured via various biomarkers in saliva.
The HPA Axis — Cortisol
The classic method of characterising a stress response is to measure cortisol levels, which rise due to a series of changes in the hypothalamic-pituitary-adrenal (HPA) axis. However, research has shown that this system can be relatively slow in responding to stress (a latency of some 10–15 minutes).
The Sympathetic Nervous System — Alpha-Amylase
Changes in the sIgA and alpha-amylase response — markers of the sympathetic nervous system (SNS) activity — are somewhat quicker. It is also well known that chronic stress with elevated cortisol levels can lead to immune suppression and reduced sIgA values.
The Diurnal Profile
In corporate and health & wellness settings it is more common to look at the diurnal profile of cortisol, typically with 5 samples taken throughout the day:
- Awakening
- Awakening +30 minutes
- Midday (~12:00)
- Around 5 p.m.
- Bedtime
Area Under the Curve
The shape and character of the diurnal profile of cortisol can give useful insight. In well-functioning individuals there is typically a sharp peak between sample 1 & 2, with minimal values in the evening. A flat profile implies chronic stress.
"When training as a professional boxer, I used to regularly take saliva samples using SOMA technology to give me and my team quick insight into training stress and immune function."Tony Jeffries — Olympic Medallist & Undefeated Professional Boxer