Though researchers have long known that stress can have negative effects on the body, it has traditionally been difficult for scientists to study the effects of stress because tracking the hormone cortisol – sometimes known as the “stress hormone” – is difficult to do in real time.
Yet researchers at Stanford University have figured out way to do just that, by using a wearable sensor capable of measuring cortisol levels through sweat.
Portable Cortisol Sensors
There have been previous attempts to track an individual’s stress level by tracking markers of stress like sweat level, heart rate, and body temperature. Yet those things can easily be influenced by factors other than stress. Cortisol is a steroid hormone tightly linked with stress, and levels of cortisol in the body spike as an individual is placed under intense physical or emotional strain. Cortisol levels can be tracked by running tests on a person’s hair, blood, or saliva, but these methods are slow and can’t give scientists the sort of real-time data that could prove helpful to them. Scientists needed a device capable of tracking cortisol levels quickly and reliably so that they could accurately discern the effects of short-term stressors.
In response to this need, researchers at Stanford set out to create a wearable device capable of measuring cortisol levels through a person’s sweat. The group of Stanford researchers, led by Alberto Salleo, an engineer and materials scientist, announced that they succeeded in creating the wearable patch in Science Advances. According to the research team, the device can reliably determine how much cortisol someone is producing by analyzing sweat under the patch in a matter of seconds.
The outer layer of the patch has small perforations in it, which pull in the sweat and hold it in a reservoir. The reservoir itself has a membrane of a top of it which lets charged ions like potassium and sodium pass through the device. Unlike these charged ions, cortisol doesn’t have a charge and can’t pass through the membrane, and ends up blocking the flow of the charged ions. The device can then be sent signals to start an electrical sensor that will detect and analyze the blockages created by the cortisol and determine how much cortisol is in the person’s sweat.
Challenges In Measuring Cortisol
The device was initially tested on runners, and the initial tests found that the data obtained by the cortisol detecting patch was an exact match for the data obtained by analyzing sweat samples from the runners, a process that typically takes a few hours. The work done by Stanford researchers could herald a substantial breakthrough in the research of stress, yet it’s effectiveness and utility won’t be known for certain until more rigorous and thorough testing has been done on the devices. According to Jason Heikenfield, co-founder of sweat sensor company Eccrine Systems and University of Cincinnati professor, determining hormone levels through sweat analysis is much more difficult than traditional lab tests where salinity and pH can be controlled. Heikenfeld explains:
Both salinity and pH vary significantly in sweat—so much that any sensor that is sensitive to ions or pH will likely change signal more due to changes in ions or in pH than to cortisol. They will need more subjects, more data points, and tests continuously on-body for at least hours.
While cortisol is a difficult thing to reliably target, the advantage of using cortisol is that it can more reliably indicate stress levels. Currently, the biggest challenge for researchers of cortisol, and for those trying to develop methods of detecting cortisol, are improving both temporal stability and thermal stability. Cortisol levels become more difficult to detect over time, and in conditions of fluctuating temperature.
Applications For The Sensor
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The next major step for the Stanford research team will be demonstrating the performance of the sensor in studies over long periods of time, and proving that the device remains reliable under various thermal conditions. The Stanford team is currently working to miniaturize the device, and also hoping to develop a user interface that will assist in the evaluation of data. The team also wants to adapt the device so that it could be powered by harvested energy rather than by an internal battery. The paper suggests that the device could be modified to detect other hormones and non-charged ions within sweat. The end goal is to have a device Is capable of monitoring several different biomarkers at the same time, which would help researchers and health professionals gain a more holistic, individualized representation of a person’s health and mental state.
There are various applications for devices that can reliably monitor cortisol levels. Analysis of cortisol levels could help researchers get an objective gauge of both physical or emotional stress within research subjects, enabling them to understand the effects of stress on the body. Doctors can also use the devices to determine if there are problems with an individual’s pituitary gland or adrenal glands. A portable device could even help those with hormonal imbalances monitor their own hormone levels at home. Devices such as these could help detect stress in young children, who are often unable to communicate their stress.
Childhood Stress
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The relationship between stress and childhood has been of great interest to researchers seeking to understand how stressful events impact the development of people – how it affects people’s risk for mental or physical health problems as an adult.
Researchers at the University of Wisconsin -Madison wanted to see how life events, particularly stressors, altered the expression of DNA through a process called DNA methylation. DNA methylation doesn’t actually alter your DNA, rather it alters how certain DNA sections may be used or expressed. The researchers collected saliva samples from 22 young girls and analyzed them to determine what biological processes were at work. The researchers discovered that there were 122 genes that saw different methylation in low-stress and high-stress children. In terms of expression, more than 1400 genes were expressed differently between low-stressed and high-stressed children, including a dozen or so of the genes that had been methylated differently.
Reid Alisch, professor of neurosurgery at UW-Madison, says that scientists haven’t been sure if molecular changes that occur in the body due to early stress are stable in later life or not. The research seems to suggest that even after 10 years or so there are still notable makers of the trauma/stress and that the trauma could potentially make people more susceptible to further trauma or behavioral changes in later life.