More and more people walk around with a smart watch that measures their stress level. That seems useful, but don’t take those scores too seriously, warns neuroscientist Denise van der Mee. ‘You also have positive stress.’
Dorine Schenk14 September 2023, 03:00
‘You have had very few moments of rest today. Slow down and relax.” Anyone who wears a smartwatch is familiar with such warnings. In addition to the number of steps and your sports activities, smart watches claim to be able to measure your stress and sleep score. But those scores are not very reliable and the heart rate measurements sometimes miss the mark, neuroscientist Denise Van der Mee and colleagues at the Vrije Universiteit Amsterdam discovered when they compared smartwatches with professional, scientific measuring equipment.
“It’s a fun toy to see how your steps, activity, calorie burn or sleep differ from day to day. But the precise values are often incorrect,” says Van der Mee. “You have to take the measurements with a grain of salt.” She wears two different smart watches herself. “I enjoy collecting and comparing my own data. My work is also my hobby.”
How well can smartwatches measure body signals?
“If you sit quietly, the heart rate measurement of a smart watch is comparable to professional measurements. But as soon as you start moving, things go wrong. If you move your wrist, it becomes difficult to pick up signals properly. I also looked at a new design with a sweat sensor. The sweat measurements also become much less reliable when you start exercising. The watches absolutely do not meet the gold standard that we demand in scientific research.”
How do smartwatches measure sleep and stress?
“They combine body measurements with personal data such as age and gender. For this they use methods that are not well substantiated scientifically. You can actually only properly map sleep phases with an EEG measurement in which an electrode cap measures brain activity. The watches use heart rate and movement. That gives an indication, but what it exactly means differs per person.”
“For the stress scores, the Garmin company says that they rely on heart rate variability. That is a measure of the time between heartbeats. Fitbit also does that, and also takes sleep score and activity from the previous day into account. There is scientific research showing that there is a link between heart rate variability and heart rate and stress. But we still know too little about that relationship to be able to say with certainty that a certain change in heart rate indicates stress. We can’t even do that with professional equipment.”
What makes stress difficult to measure?
“By ‘stress’ we usually mean negative emotions. But in science, stress only says something about your alertness. That doesn’t have to be negative. You also have positive stress, for example, where you are enthusiastic and focused. With both positive and negative stress you see an increase in heart rate and a decrease in heart rate variability. At the moment we cannot tell from body measurements whether someone is enthusiastic and concentrated or irritated and aggressive. Smartwatches can’t do that either. For example, when my husband is gaming, his watch indicates that he is stressed, while he does not experience it that way.”
Why is it important to distinguish positive and negative stress?
“Negative stress has been widely researched. We know that it can have negative health consequences, such as an increased risk of cardiovascular disease. Positive stress has been less well researched, but the assumption is that it does not have these adverse effects.”
Is it bad that stress scores on smartwatches are incorrect?
“Some people take those scores very seriously and that can have consequences. A friend said that she no longer wears her smartwatch because her stress score was always high. There are also people who find it difficult to interpret their own body signals. If they accept such a stress score as true, it can worsen the problem. My advice is therefore: don’t look at the stress score. I find it strange that there is no legislation for this. Companies can claim that you can regulate your stress with their device, while that is not yet possible.”
Should we even want to know our stress score?
“It can be useful. People with a burnout often say afterwards that they had seen it coming, because they had palpitations or other complaints. But society is so rushed these days that we no longer listen to our bodies. A gadget that helps with this can ensure that you intervene or seek help in time. And neurodiverse people, with ADHD, autism or bipolar disorder, for example, can benefit from it because they have more difficulty properly picking up signals from their body.”
“It is also interesting for research. Current measuring techniques, with electrode stickers and measuring boxes, are not suitable for long-term measurements in everyday life. Watches do. That’s why we hope the technology gets better. But time will tell whether it is ever feasible to measure stress with a smartwatch.”
Neuroscientist Denise van der Mee.
CV: Denise van der Mee (05-05-1990, Ter Aar)
2002-2007 havo
2007-2010 propaedeutic teacher training in biology
2011-2014 bachelor Health & Life Sciences (cum laude)
2014-2016 master neuroscience (cum laude)
2016-2023 PhD/PhD in Biological Psychology, Vrije Universiteit Amsterdam
2023-present postdoc Developmental Psychology, Vrije Universiteit Amsterdam
Also read
2023-09-14 01:00:30
#smartwatch #warn #stress #youre #focused
