Stressful working conditions - in particular those experienced by many professionals during Covid-19 pandemic - can lead to a psychic disorder known as "burnout syndrome". Physical and emotional exhaustion are the main symptoms, a new wearable device can detect high levels of stress by analyzing sweat.

Developed by engineers from the Federal Polytechnic School of Lausanne (EPSL), Switzerland, in partnership with the startup Xsensio, the device can be applied directly to the patient's skin to continuously measure the concentration of cortisol, the main stress biomarker. The device, described in a study published in Nature, can help doctors better understand and treat conditions like burnout and obesity.

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Blood tests are often used to take instant measurements of patients' cortisol levels. However, detectable amounts of the hormone can be found in saliva, urine and sweat.

Cortisol is produced by the adrenal glands from cholesterol. Its secretion is controlled by the adrenocorticotrophic hormone (ACTH), which is produced by the pituitary gland. It performs essential functions in our body, such as regulating metabolism, blood sugar levels and blood pressure; it also affects the immune system and cardiovascular functions.

Device created at EPFL is capable of measuring the concentration of cortisol in the user's sweat. Image: CGN089 / Shtterstock

In stressful situations, cortisol instructs our body to direct the necessary energy to our brain, muscles and heart. "Cortisol can be secreted on impulse - you feel good and suddenly something happens that puts you under stress and your body starts to produce more of the hormone," explains Adrian Ionescu, head of the EPFL Nanoelectronic Devices Laboratory (Nanolab).

Usually secreted throughout the day according to a circadian rhythm, with a peak between 6 am and 8 am, cortisol gradually decreases in the afternoon and at night. "But in people who suffer from stress-related illnesses, this circadian rhythm is completely altered," says Ionescu.

"If the body produces too much or not enough cortisol, it can seriously damage an individual's health, which can lead to obesity, cardiovascular disease, depression or exhaustion", adds the researcher.

The patch developed by EPFL's Nanolab contains a transistor and an electrode made of graphene, which has high sensitivity and very low detection limits. This is the first system developed to monitor cortisol concentrations continuously throughout the circadian cycle.

“This is the main advantage of our device. As it can be used on the skin, scientists can collect quantitative and objective data about certain stress-related illnesses in a non-invasive, accurate and instantaneous way ”, says Ionescu.