Sleep disorders and inadequate sleep are major global problems that contribute, for example, to increased health costs and sick leave, as well as a reduced quality of life. According to recent estimates, sleep apnea alone affects around 1 billion people worldwide, and up to half the world’s population will experience insomnia at some point in their lives. In Finland alone, sleep apnea is estimated to affect the lives of nearly 1.5 million people, although most of them go undiagnosed. Simpler and cheaper methods of screening and diagnosing sleep disorders are urgently needed.
A recent review by the Sleep Technology and Analytics Research Group, STAR, at the University of Eastern Finland examined future trends in sleep disorder measurement technology and focused on the possibilities of measurement at home. Polysomnography, currently performed in sleep laboratories in specialized health care facilities, is the most comprehensive method for diagnosing sleep disorders. However, because of the high price and limited availability of laboratory polysomnography, other methods, such as simple home-made sleep tracking, are also used in diagnosing sleep apnea. Technological advances in measurement technology and in analysis methods based on machine learning and artificial intelligence enable the use of simpler and more cost-effective measurements in the hospital environment without impairing clinical accuracy. Research has developed a number of automated methods of analyzing sleep records, the introduction of which into clinical practice could free up healthcare resources. In addition, simpler sensors could enable sleep recordings over several nights and thus provide a more precise picture of the natural structure of sleep. Self-performed sleep recordings at home cannot completely replace a comprehensive polysomnography in the sleep laboratory, but their use will certainly increase in the future.
With the current technology used in home self-administered sleep tracking, determining the exact structure of sleep is a challenge. Traditionally, stages of sleep are identified using the electroencephalogram (EEG). However, EEG is typically not included in self-administered sleep records at home because current clinical electrodes require extensive skin preparation and precise placement in various areas of the head prior to application.
A current study by the STAR group examined the electrical properties of new types of dry textile-based electrodes and the quality of the EEG signal they record. The study showed that dry electrodes take a longer time to establish stabilized electrode-skin contact than silver / silver chloride electrodes, which are widely used in clinical practice. However, when measurements were taken in laboratory settings, it was found that the EEG signal recorded by textile electrodes corresponded well to the quality of the signal recorded by clinical electrodes.
“Textile electrodes are much easier to handle and more patient-friendly and therefore a practicable alternative for self-used sleep recording at home”, Early Stage Researcher, first author Matias Rusanen, from the University of Eastern Finland says.
Better quality measurement methods at home can also be useful for monitoring the progression of sleep apnea, since the severity of the disease typically develops over several years. Breathing pauses in sleep apnea usually lead to a temporary drop in blood oxygen saturation, which puts a heavy strain on the patient’s body at night. It has been found that this so-called hypoxic exposure also predisposes patients to many other diseases such as diabetes and cardiovascular disease.
Another recent study by the STAR group examined the reverse causality of how existing diseases affect the development of hypoxic stress over several years. The study showed that in patients with diabetes or cardiovascular disease, the worsening of nocturnal hypoxic stress during a follow-up period of five years was significantly greater than in patients without comorbidities, which are typically associated with sleep apnea.
“Our results suggest that patients with diabetes or cardiovascular diseases could benefit from screening and, in particular, continuous monitoring of sleep apnea and thus from the necessary treatment,” said Early Stage Researcher, first author Tuomas Karhu from the University of Eastern Finland says.
Since comprehensive polysomnography is an expensive and complex measurement, it is not very suitable for continuous monitoring. A solution to this problem could be the methods presented above, in which the sleep of the patient is monitored by self-attached and reusable sensors in the home environment.
A laboratory comparison of a FocusBand EEG device and textile electrodes with a medical system and wet gel electrodes
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