Stress Score
What is the Stress Score?
The Stress Score shows you how much stress you accumulated during a given day.
Why is the Stress Score important?
Stress is something everyone experiences daily in today's world. Many complain that their life is too stressful and that stress decreases their quality of life (Marshall et al. 2008), their work performance (Arifi et al. 2022), etc. When it comes to dealing with stress, the first step is to find out how much stress you actually experience. This is where the Stress Score comes in.
How do I interpret the Stress Score?
This is quite straightforward. The higher your Stress Score the more stress you have experienced in one day.
What is optimal?
Let’s be clear. We have the opinion that stress should and cannot be reduced to zero (Friston, Thornton, and Clark 2012). Stress is necessary for development. But the key, especially with stress, is balance. Your optimal stress level is reflected by your Stress Zone. You can read more about the Stress Zone here.
Measuring Stress
It is not easy to measure stress, because stress is not something purely objective. Still, there are basic physiological principles we can make use of to make measuring stress with wearables not only possible but also convenient.
Why HRV measurements during the day are crap
Most of the time one value is used to measure the stress a person experiences: HRV (heart rate variability).
But the measurement of HRV comes with some big caveats.
First - Artifacts: If the location where the HRV is measured (e.g., finger or wrist) is moving, a ton of artifacts will be created, which makes an accurate measurement almost impossible. So to get accurate data users need to do a manual HRV-measurement, which means sitting still for at least one minute and doing nothing, every time when he wants to know how stressed he is.
Second - Confounding factors: The act of sitting still and doing nothing itself influences the HRV. Then it might not accurately represent the current stress level.
Third - Consistent conditions: You need consistent conditions. Did you drink something or not? Did you have coffee or not? Did you move just before or not? Did you eat something or not? Any of these factors (and there are more) influence the HRV. This is why it is recommended to do HRV-Stress-Measurements always at the same time under consistent conditions, e.g. after getting out of bed in the morning.
So if you want to use HRV to measure stress during the day (night is a separate topic), you have to do it right, or not do it at all.
How we measure stress
We use two more stable metrics: Heart rate and ambient noise.
An increase in your heart rate is a classical sign of the activation of your sympathetic nervous system, which gets activated by stress (Huang et al. 2013). Also, an increase in ambient noise is a known stressor (Westman and Walters 1981; Hammersen, Niemann, and Hoebel 2016).
By using heart rate and ambient noise we not only have measurements that are stable but they can also be measured in the background.
“So does my Stress Score increase every time my heart rate increases or when it gets loud around me? This would mean going to the gym increases my Stress Score, right?”
Nope. This is not the case.
Why? We only use an elevation of your heart rate or the noise around you as a marker of stress when you are sitting and not moving (like walking, exercising, driving, etc.).
So, think of situations when your heart rate rises or it gets noisy and you are sitting. When does this happen?
You have an upcoming deadline for an important project = Stress
You have a meeting with a lot of discussions = Stress
You argue with your spouse or children
To summarize: The Stress Score increases when two conditions apply at the same time. Either you are inactive and your ambient noise levels are above baseline or you are inactive and your heart rate is above baseline.
This means, that only if you are inactive (e.g. sitting at your desk) and there is an increase in heart rate or ambient noise above your baseline, your stress score rises.
What other metrics are influenced by the Stress Score?
The Stress Score has a direct impact on the following metrics: Stress Zone and Mindfulness Zone
How?
The higher your stress level was on previous days, the lower the recommended amount of stress you should have will be. This is why a higher Stress Score will lower your Stress Zone in the next few days. Our reasoning here is that we want to help you prevent having chronic stress, which has multiple negative health implications (Mariotti 2015).
Also, it is known that mindful activities are a great antidote to stress (Praissman 2008). Therefore an increase in your stress level will also increase the amount of mindfulness we recommend you to do.
References
Arifi, Deborah, Norman Bitterlich, Michael von Wolff, Dagmar Poethig, and Petra Stute. 2022. “Impact of Chronic Stress Exposure on Cognitive Performance Incorporating the Active and Healthy Aging (AHA) Concept within the Cross-Sectional Bern Cohort Study 2014 (BeCS-14).” Archives of Gynecology and Obstetrics 305 (4): 1021–32. https://doi.org/10.1007/s00404-021-06289-z.
Friston, Karl, Christopher Thornton, and Andy Clark. 2012. “Free-Energy Minimization and the Dark-Room Problem.” Frontiers in Psychology 3. https://www.frontiersin.org/article/10.3389/fpsyg.2012.00130.
Hammersen, Friederike, Hildegard Niemann, and Jens Hoebel. 2016. “Environmental Noise Annoyance and Mental Health in Adults: Findings from the Cross-Sectional German Health Update (GEDA) Study 2012.” International Journal of Environmental Research and Public Health 13 (10): 954. https://doi.org/10.3390/ijerph13100954.
Huang, Chun-Jung, Heather E. Webb, Michael C. Zourdos, and Edmund O. Acevedo. 2013. “Cardiovascular Reactivity, Stress, and Physical Activity.” Frontiers in Physiology 4 (November): 314. https://doi.org/10.3389/fphys.2013.00314.
Mariotti, Agnese. 2015. “The Effects of Chronic Stress on Health: New Insights into the Molecular Mechanisms of Brain–Body Communication.” Future Science OA 1 (3): FSO23. https://doi.org/10.4155/fso.15.21.
Marshall, Leisa L., Amy Allison, Diane Nykamp, and Shankar Lanke. 2008. “Perceived Stress and Quality of Life Among Doctor of Pharmacy Students.” American Journal of Pharmaceutical Education 72 (6): 137.
Praissman, Sharon. 2008. “Mindfulness-Based Stress Reduction: A Literature Review and Clinician’s Guide.” Journal of the American Academy of Nurse Practitioners 20 (4): 212–16. https://doi.org/10.1111/j.1745-7599.2008.00306.x.
Westman, J C, and J R Walters. 1981. “Noise and Stress: A Comprehensive Approach.” Environmental Health Perspectives 41 (October): 291–309.