Human sweat contains all kinds of valuable biomarkers that can be used to track different aspects of human health, such as glucose levels in diabetics or metabolic conditions during exercise, and a new breed of wearable sensors promise to make this a rather simple undertaking. Scientists at Switzerland’s École polytechnique fédérale de Lausanne (EPFL) have just developed the first of these designed to continuously monitor stress levels over the course of the day, which they hope will make it easier to spot signs of stress-related disease caused by disruptions to natural hormonal cycles.
The research focuses on the hormone cortisol, which can spike in response to stressful events but is also secreted naturally throughout the day in line with our circadian rhythm. Levels peak between 6 am and 8 am and gradually decrease over the course of the day, playing an important role in regulating things like blood sugar, blood pressure and metabolism.
“But in people who suffer from stress-related diseases, this circadian rhythm is completely thrown off,” says Adrian Ionescu, who led the research team. “And if the body makes too much or not enough cortisol, that can seriously damage an individual’s health, potentially leading to obesity, cardiovascular disease, depression or burnout.”
Back in 2018, we looked at research from Stanford University that resulted in the first wearable skin sensor that could measure a person’s cortisol levels through their sweat. Where this patch was designed to be applied momentarily to the subject when they are glistening in sweat to gather the sample for analysis, the EPFL team sought a solution that could be worn around the clock.
At the heart of the breakthrough is the high sensitivity and very low detection limits of the patch, owing to an electrode made from graphene that can bind to and capture cortisol, working with a transistor to measure its concentration in the wearer’s perspiration. This is the first system developed to continuously track cortisol concentrations across the circadian cycle, opening up some very useful possibilities.
“That’s the key advantage and innovative feature of our device,” says Ionescu. “Because it can be worn, scientists can collect quantitative, objective data on certain stress-related diseases. And they can do so in a non-invasive, precise and instantaneous manner over the full range of cortisol concentrations in human sweat.”
The patch has been put through its paces in the lab and the team is now planning on testing it out at a local hospital on patients suffering from stress-related conditions, such as Cushing’s syndrome, Addison’s disease and obesity. Furthermore, they believe the technology can play a role in diagnosing and treating psychological diseases brought on by stress.
“For now, they are assessed based only on patients’ perceptions and states of mind, which are often subjective,” says Ionescu. “So having a reliable, wearable system can help doctors objectively quantify whether a patient is suffering from depression or burnout, for example, and whether their treatment is effective. What’s more, doctors would have that information in real time. That would mark a major step forward in the understanding of these diseases.”
The research was published in the journal Communications Materials.
First-of-a-kind sweat sensor tracks stress levels around the clock [New Atlas]