Part II: Skin conductance
Skin conductance, also known as electrodermal activity (EDA) is based on the theory that skin conductance varies with the status of the sweat glands in our skin. This means that the skin will better conduct electricity when the sweat glands are more active. And since the status of the sweat glands is regulated by the sympathetic nervous system, it can be related to mental status. In this blogpost, you can read more about the physiology behind skin conductance measurements, about some interesting applications and I will briefly give some limitations of this technique.
So how does a stress monitor based on skin conductance work? In fact, skin conductance can only reliably be measured on the palms of the hands and soles of the feet. The reason is simple, nowhere else in the body there is such a high density of eccrine sweat glands that are know to respond to mental arousal. A device that measures skin conductance usually consists of two electrodes that are placed on the skin. A small electrical current is sent via the skin from electrode 1 to electrode 2, and the more an individual is aroused, the better the conductivity of the skin. This is what a stress monitor based on skin conductor measures and is caused by a slightly increased perspiration of the skin, since perspiration consists of water and electrolytes.
Let’s now discuss some of the most recent developement regarding the use of skin conductance measurements to detect and alleviate stress. Melander et al. (2017), just published a paper in which they described their attempt to identify agitation in individuals with Dementia. Therefore, they equipped nine Dementia patients with an EDA sensor. The nurses recorded the behaviour of the patients at the same time. Correlations were identified between what the nurses observed and what the sensor registrated. The researchers found a correlation between both variables at the moment that the nurses made the observation as well as 1 and 2 hours prior that moment (p<0.01). Important to notice: there was also a significant difference in mean sensor value between individuals showing agitation and individuals that were assessed by the assistants as awake/calm. The results show that based on this technique, agitation in individuals with Dementia can be detected earlier than it is usually observed. Please find the link to the paper here.
Another commercial application is the Moodmetric ring. This ring shaped stress monitor, claims to measure both stress and recovery. It comes together with an app on your phone where you can see the measurement in real-time, and a Moodmetric ring that probably gives some information about your mood. If you want to know more about this ring, then there is a scientific paper where they assess the ring as a research tool. You can find the link here.
One of the challenges for this methodology is that situations of high arousal can have both a positive and negative origin. In the example of individuals suffering from Dementia, it is important to know whether someone is happy, and therefore aroused, or angry aroused. Therefore, the nurses are irreplacable when it comes to the interpretation of what’s just measured. As you see, there is still food for thought, and there are still some obstacles to overcome. But who knows what will happen in 2018!
Next week’s blogpost: Stress monitoring through heart rate variability.
This blog was originally posted here.