A new sensor that detects amounts of cortisol in sweat can identify stress levels.

Researchers have successfully tested wearable sweat sensors that can precisely assess levels of the stress hormone cortisol in the body. It has been discovered that the amounts of cortisol found in sweat reflect the levels found in the blood.

Many people believe that sweat will be one of the next frontiers in the field of wearable electronics. Every drop of this fluid has its own unique story to tell about what is inside the body. Sweat can convey information about several health conditions, including dehydration, stress, muscle cramps, high cholesterol, depression, and even blood glucose levels.

Cortisol, which is often known as the “stress hormone,” can be measured using this tool. When exposed to the drug for an extended period at high concentrations, one risks developing various health problems, including type 2 diabetes, high blood pressure, and disturbed sleep. Because of this, it is essential to maintain a low level of stress in your life.

There is a variety of wearable technology, such as fitness trackers and smartwatches, that can quantify stress levels. They accomplish this by measuring heart rate variability (HRV), which refers to the variation in the amount of time that passes between each heartbeat. The greater the worth, the less stressful the situation. It is impossible to determine which came first, the exhaustion or the strenuous activity because both have the same effect on heart rate variability (HRV).

On the other hand, a more favorable outcome might be just around the corner.

Devices were worn on the body that measured cortisol

Early in the year 2020, we published an article discussing findings from Caltech. They have invented a graphene sweat sensor capable of directly measuring the levels of cortisol present in a person’s body. Cortisol can be discovered in sweat due to its small molecule size, which allows it to disperse and be found in sweat. The concentration levels found in the fluids are an accurate representation of those found circulating throughout the body.

At one end of the technology is a sheet of plastic with very small laser-generated pores that are designed to collect sweat. This goes through an antibody, which is a sort of molecule found in the immune system. This antibody is particularly sensitive to cortisol, so it can detect it when it is there.

Wei Gao, an assistant professor in the medical engineering department at Caltech, was the primary author of a work entitled “Investigation of cortisol dynamics in human sweat utilizing a graphene-based wireless mHealth system.” You may find it in the issue of Matter that was published in April of 2020. The Matter is a content studio that was founded by Evan Williams, the pioneer of Twitter.

The technology can work in real time and can be produced in large quantities. It has the potential for widespread usage for measuring stress and detecting anxiety, post-traumatic stress disorder, and depression because it is affordable, does not involve any invasive procedures, and is accurate. There is a connection between increased cortisol levels and all of these factors.

“Depression sufferers have a distinct circadian pattern of cortisol than healthy individuals do,” Gao adds. “[T]hey are more likely to experience symptoms of depression.”

Patients who have PTSD provide a unique challenge in this regard.

In addition, the analysis can be completed in a fairly short time. In contrast to conventional blood tests, the findings of this one are accessible in a matter of minutes.

A blood test will often take between one and two hours and necessitate having one’s blood drawn, which can be stressful. “Time is of the utmost importance for managing your stress levels,” he stated.

“We want to create a wearable device that is capable of collecting multimodal data, including information on vital signs as well as molecular biomarkers,” he explains. “Our goal is to do so.”

Two distinct methodologies were utilized to validate the technology. The first one consisted of watching a person around the clock for a period of six days. Cortisol levels go through a cycle of rising and falling throughout the day, with greater values often being seen in the morning. The information that was dispensed by the sweat sensor was found to correlate with this natural cycle. The second method involves subjecting the individual to additional strain by performing strenuous exercise in one test and then exposing them to cold water in another. Both are linked to elevated levels of the stress hormone cortisol, as demonstrated by the study’s findings.

This is not the only experiment that was effective. Technology comparable to this was discussed in the issue of Science published in January 2022. It concerns a wristwatch that can measure cortisol levels and be produced by researchers at UCLA (University of California, Los Angeles).

Given that all of this research was conducted at California institutions, we cannot determine whether this is a clever piece of technology or only an updated version of the item that will be released in 2020. By analyzing perspiration, the wearable device provides a non-invasive, accurate, and real-time measurement of cortisol levels, as demonstrated in the image below.

The researchers have constructed a flexible field-effect transistor (FET) biosensor array. This array makes use of a previously unknown cortisol aptamer. You can learn everything there is to know about it by following this link, but a word of caution: the content is rather technical.

“label-free detection,” “the sensing device is autonomous and wireless,” “the cortisol detection limits are ultralow (1 pM”), and “they confirmed sweat cortisol as a stress biomarker in a major clinical investigation” are some of the benefits that come with using this wearable. The researchers tested the data by connecting the sweat sensor to an Android app.

They go on to say that monitoring the relative changes in an individual’s biomarkers over the course of their life is more significant than taking single readings for wearable applications. This is because individuals’ baseline levels of cortisol are not the same. This might alter further down the road once sufficient data has been collected to enable further in-depth research. For the time being, you can think of it as how a Fitbit monitors your skin temperature. The instrument is more concerned with measuring fluctuations than absolute values.

Our takeout

Will a device similar to this one be incorporated into the future iteration of Garmin or Apple Watch? The answer to this question will be no, at least not until the year 2022. However, there is no doubt that this will occur shortly. The application of this kind of technology has the potential to revolutionize medical treatment.

Although therapeutic applications of sweat can be traced back to the 1950s, the Science of sweat is still in its early phases. At least for the time being, it is still a biofluid that has been relatively little investigated.

Our analysis of what Gatorade has been doing on this front was recently published. Their sweat patch is not measuring the cortisol level. Instead, the product examines the variations in hue brought about by chemical processes to determine both the level of dehydration and the concentration of chloride within the body.

We will eventually have access to smartwatches that are capable of providing information of this nature. But we are not quite there yet; that day is still a few years away.

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