The newest wearables are using sweat to track stress – that’s how it works

Almost a year after the pandemic started, it seems like the right time to commit to keeping stress levels under control. (If not now, right?) And because we are a culture obsessed with personal data (aware of our step count, calories consumed and hours of sleep), it’s not exactly surprising that the newest wearables on the market are tracking stress. While different tech companies are doing it in different ways, a promising method is to track stress through sweat – which is how Fitbit Sense ($ 279) does it.

While hectic and cool, many people want to know exactly how this kind of new technology works before spending $ 300 – especially considering that if you’re stressed to the point that your shirt gets soaked, you don’t exactly need a wearable to tell you that you need to calm down. Although sweat stress is a new concept for most, it is something that nanotechnology researcher Mihai Adrian Ionescu, PhD, head of Nanolab and professor at the Swiss Federal Institute of Technology, has been studying for some time – and has just published an article explaining the connection in the magazine Nature. Here, together with Fitbit research algorithm scientist Belen Lafon, PhD, he gives more information.

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sweat stress

How Stress Sweat Tracking Works

Dr. Ionescu explains that stress – both physical and mental – triggers a response throughout the body, preparing you to face the stressor. One such answer is sweat. But when we sweat, it’s not just water running out of our pores. Cortisol – also known as a stress hormone – is also excreted. Cortisol, he says, can be detected in our blood, sweat, saliva and urine. (Aren’t you happy that the latest wearables aren’t monitoring your pee?)

In Dr. Ionescu’s experiments, his team created a chip that detects changes in cortisol through sweat. “This process is very sensitive and effective for quantifying very small changes in concentration,” says Dr. Ionescu. In other words: the chip detects minimal changes in cortisol levels; you don’t have to be sweating a lot to detect that you are experiencing stress.

Here’s another thing to keep in mind about cortisol: cortisol levels naturally fluctuate over 24 hours. (They are usually higher in the morning when you wake up and lower at the end of the day.) Dr. Ionescu says his team’s technology takes this into account, as well as whether someone is secreting cortisol because of physical activity. “Abnormal levels of cortisol can be generated by stress, but also by intense physical activity,” he says. “There is a circadian rhythm of cortisol, but we know the ‘normal’ limits very well … In addition, the technology will allow quantitative measurements in a few days, so the repetition of monitoring for abnormalities can confirm that it is due to stress.

For example: if you meet your boss every day at 2 pm, the technology can detect a change in cortisol levels during that time. Since this is not a time of day when cortisol levels normally rise in humans and you are not training, the logical conclusion is that changes in cortisol are due to mental stress.

Dr. Lafon says that Fitbit’s technology takes a different approach. “We approach stress management holistically, which is why we don’t simply track the rise and fall of hormones or individual bioindicators, such as cortisol,” she says. Instead, she says the Fitbit Sense is the first smartwatch with a sensor that detects electrodermal activity (the variation in the skin’s electrical conductance in response to sweat secretion).

“Since sweat is good at conducting electricity, the more sweat you have, the easier the electrical current will flow from one of the Sense electrodes to the other, allowing us to measure the conductance of the skin, also known as the EDA response”, she says. . “Sweat can be generated by different mechanisms, one of which is through small sweat waves – so small that they are generally not perceived by us as being ‘sweaty’. These waves can be measured by Sense, and each one is what we call the EDA response. Measuring these responses can help users understand their body’s response to stressors and can help them manage their stress. “

The smartwatch also uses heart rate and sleep activity in conjunction with this to give an overall “stress” score. “Sense users with Premium are able to see skin temperature variation minute by minute while they sleep to see how their skin temperature changes during the night,” explains Dr. Lafon.

Dr. Lafon emphasizes that electrodermal activity is the main stress monitoring factor for the device, with heart rate and sleep patterns also playing a role. This, she believes, gives a more complete picture of someone’s stress compared to just the changes in cortisol.

You have the data, what now?

Your wearable stating that you are stressed is not exactly a solution: it is also important to know what to do with the information. “Stress is an almost universal experience, with more than a third of people worldwide reporting the physical and mental side effects of stress,” said Dr. Lafon. “Especially during COVID-19, understanding and managing your body’s stress response is more important than ever to avoid long-term impacts on your health and well-being,” she adds, emphasizing that she believes that understanding the body’s response stress is the key to managing this. If a Fitbit Sense user gets a below average stress score, she says the Fitbit app will offer practical recommendations on how to get the score to a better place, such as mindfulness and meditation recommendations. (Fitbit Premium offers mindfulness sessions with Headspace.)

Although Dr. Ionescu’s chip is not yet on the market as a product, he is personally enthusiastic about the technology’s potential to improve health. “[This type of technology] opens the untapped ‘3 Ps’ of healthcare: preventive, personalized and participatory, “he says.” This will help providers provide the best therapy at the right time and enable preventive approaches, “says Dr. Ionescu. For example, a wearable can detect that someone is stressed before they know it. So this information can be used to cut the bad at the root before it gets worse. Armed with the information, someone will know that they really need to focus on managing stress in whatever ways work for them, whether through exercise, meditation or therapy.

This evolving technology is yet another example of how wearables are learning more about us than we know about ourselves. You have no idea how far you walked while taking the dog for a walk? Check your stats. Wondering if you same slept eight hours last night? Technology keeps the score. And now you can use it to assess when you need to relax. The only remaining question: what will this tell us next?

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