More Accurate than a Smart Watch with Sleep Sound

A sleep tracker is an over-the-counter tool that allows you to monitor your sleep by measuring your sleep stages each night in the simplicity and comfort of your own home. By routinely monitoring our own sleep with a sleep tracker, we can see how we sleep each night. We can see if there are any objective problems with our sleep patterns or sleep efficiency, how we can address them, how objective sleep efficiency correlates with subjective sleep satisfaction, and even seek appropriate professional help if needed.

If you want to get a real impact by using sleep tracker to maintain or improve sleep quality, in addition to being convenient enough to use on a daily basis, the sleep data it provides must be accurate because the interventions you need will vary depending on how you sleep.

For example, if you take a long time to get into bed and fall asleep (sleep onset time), you may need an intervention that reduces this time, or if you fall asleep but wake frequently (wakefulness), you may need an intervention that reduces these awakenings. Because there are so many factors that can affect sleep quality, and because everyone experiences different symptoms, the most important thing we can do to recommend an effective intervention is to understand your exact sleep data.

For effective sleep improvement services, you need accurate sleep data

Accurate sleep data means that analyses are accurate for each sleep stage: Sleep (deep/light) - Wake - REM.

As the state of sleep is ultimately a state of the nervous system, each stage of sleep can be identified by the degree of activation of the brain's nervous system (central nervous system) and the motor nervous system. For example, during wakefulness, both the motor and cerebral nervous systems are active, whereas during REM sleep, the motor system is stable but the cerebral nervous system is active.

In order to accurately determine the state of each stage of sleep - deep/light - wake - REM - it is necessary to be able to accurately determine the state of both the cerebral and motor nervous systems.

Each sleep trackers on the market track and analyse each of the stages of sleep - deep/light, wake and REM - in different ways.

Widely used sleep trackers — smartwatches and smart rings — track very simple movements, such as when you're up and awake, using signals called actigraphy. But this method alone makes it difficult to accurately track and analyse each stage of sleep. Because actigraphy only tracks movement through an accelerometer, it can't track changes in the motor nervous system, which is a huge weakness - for example, if you're not normally a light sleeper, the time you spend lying still in bed trying to sleep - that is, lying there as if you're asleep when you're not - is also measured as 'sleep'. Modern smartwatches and smart rings have compensated for the limitations of actigraphy by adding the ability to track the state of the brain's nervous system through heart rate variability (HRV), allowing more accurate tracking of sleep stages.

But even here there are weaknesses. For a sleep tracker to really help you improve your sleep, the sleep tracker you use needs to be able to accurately track each of the sleep stages: sleep (deep/light) - wake - REM, and for each sleep stage to be accurate, it needs to be able to accurately determine the state of both the brain's nervous system and the motor nervous system. In particular, the REM and Wake phases cannot be distinguished by determining the state of the cerebral nervous system using Heart Rate Variability (HRV), because the cerebral nervous system is active during both REM and Wake phases. In this case, REM and Wake phases can be distinguished by determining the state of the motor nervous system.

Can sleep tracker detect the condition of cerebral and monitor nervous systems?

Among the various sleep trackers on the market, Asleep's 'Sleep Routine' analyses the sound of your breathing during sleep to determine the state of your cerebral and motor nervous systems. The rhythm/periodicity/pattern of your breathing indicates the state of your brain, and the tone/tone/depth of your breathing indicates the state of your motor system. Based on the activation of the brain and motor nervous system, we can identify the stages of sleep (Deep/Light) - REM - Wake.

During sleep we breathe unconsciously. The nervous system controls breathing, and when breathing is controlled, the nervous system stabilises. Therefore, the stability of breathing and the stability of the nervous system (the stability of sleep) are highly correlated. Therefore, the state of the brain and motor nervous system that controls breathing during sleep is reflected in the sound of breathing. In particular, even a small change in the state of the motor nervous system changes the shape of the airway. Even a small change in the airway changes the tone, timbre and depth of the respiratory sound.

Determining the state of the brain's nervous system through the rhythm/periodicity/pattern of breathing is similar to determining the state of the brain's nervous system through heart rate variability (HRV), the patterned cycle of the heartbeat. However, subtle changes in the motor nervous system, which is one of the key pieces of information for more accurate identification of each sleep stage, can be identified through the tone/depth/timbre of your breathing. That's a lot more information than many other sleep trackers collect about your sleep.