SleepLoop subconsciously enhances deep sleep

The SleepLoop system emits a sound at the right time to amplify the slow brain waves. (Credit: SleepLoop)

Researchers have developed a wearable device that plays specific sounds to enhance deep sleep.

The first clinical study of the device has now shown that it is effective, but not at the same level of effectiveness for everyone.

Many people, especially the elderly, suffer from abnormal sleep. In particular, the deep sleep phases become shorter and shallower with age. Deep sleep is important for the regeneration of the brain and memory, and also has a positive influence on the cardiovascular system.

Researchers have shown that the brain waves characterizing deep sleep, so-called slow waves, can be improved by playing precisely timed sounds through earphones while sleeping. While this works well in the sleep laboratory under controlled conditions, there has thus far been no at home solution that can be used longer than just one night.

That’s where SleepLoop comes in.

The SleepLoop system consists of a headband that is put on at bedtime and worn throughout the night. This headband contains electrodes and a microchip that constantly measure the brain activity of the person sleeping. Data from this is analyzed autonomously in real-time on the microchip using custom software.

As soon as the sleeping person shows slow waves in the brain activity characterizing deep sleep, the system triggers a short auditory clicking signal. This helps to synchronize the neuronal cells and enhance the slow waves. What makes the solution unique is that the person sleeping is not consciously aware of the sound during deep sleep.

For a first clinical study, researchers equipped participants, between 60 and 80 years old, with the SleepLoop system, which they were required to operate themselves in their own home. The system is designed to function independently even by users with little technical experience.

“This worked very well. We had surprisingly little data loss and the participants rated the device as user-friendly,” says Caroline Lustenberger. group leader at the Neural Control of Movement Lab at ETH Zurich.

Participants wore the device every night for four weeks, with the auditory stimulation given on a nightly basis for two weeks and no stimulation for the next two weeks. Neither the subjects nor the researchers knew in which two weeks the auditory signals were played and in which two they were not.

The results of 16 participants of the study show that it was indeed possible to enhance the slow waves through auditory signals during deep sleep in most participants. However, individual differences were extensive with some subjects responding very well to the stimuli, while others responded minimally or not at all.

The question of whether a person reacted to a stimulus did not depend on their well-being during the day, Lustenberger says.

“Some people generally responded well to the stimuli and clearly showed enhanced slow waves, while others showed no response, regardless of their daily well-being.”

The researchers have used these individual differences to better predict how a given individual will respond to the auditory stimulus. This in turn helps them to optimize and improve the performance of SleepLoop.

A spin-off company Tosoo AG, is currently working on developing the device further and preparing it for the clinical market. It is already clear that it will not be freely available, but only via a doctor’s prescription.

“This is a medical device, not just a wellness consumer product you can order online when you have trouble sleeping,” says Walter Karlen, who developed the technology at ETH Zurich, and is currently director of the Institute of Biomedical Engineering at Ulm University.

“Use of the device must be medically indicated and supervised by a doctor,” he says. Further development of the technology will now continue also in Ulm.

The study appears in Communications Medicine. Additional coauthors are from the University of Zurich and Ulm University.

Source: ETH Zurich