Sleep & Tech

Wearable vs Nearable vs Airable

|by Asleep

    [Editor’s Note]

    Getting a Polysomnography (PSG) at the hospital can be quite a hassle. It takes over 8 hours, and you need to attach various testing devices all over your body. To get insights into your sleep patterns, a single day's test often isn't enough.

    Is there a way to easily measure your sleep quality every day at home? Various sleep trackers available in the market might just be the alternative. In this article, we introduce Asleep, which utilizes various biological signals for commercial sleep trackers.

    If you've ever been curious about your sleep quality, you've probably tried searching for a solution. Sleep trackers are devices designed to do just that: track your sleep patterns.

    The advantage of sleep trackers is that you can purchase the device and use it at your convenience without needing to visit a hospital. Of course, sleep trackers can't fully replace a Polysomnography (PSG). However, they provide valuable information about sleep stages and more, making them quite useful. Some devices even come close to PSG in terms of accuracy.

    Commercial sleep trackers currently on the market employ various methods and operating principles for measuring biological signals. We discussed the classification based on these factors in our previous article, "Sleep Technology: Gadgets and Products Designed to Enhance Sleep." In this article, we'll classify them into three main categories based on user accessibility and convenience.

    1. Wearable

    A wearable sleep tracker refers to sleep tracking devices that can be worn like clothing or shoes. Examples of such devices include smartwatches like Galaxy Watch, Apple Watch, and Google Pixel Watch, as well as ring-type devices like the Oura Ring.

    What these sleep trackers commonly provide is information about sleep stages. To accurately assess sleep quality and state, monitoring sleep stages is crucial.

    Sleep can be broadly divided into four stages, ranging from being awake to REM sleep, light sleep, and deep sleep. While polysomnography (PSG) attaches electrodes to the head and chest to measure sleep stages through EEG and ECG tests, wearable devices have come up with more convenient methods. LG Electronics has released sleep management earphones that measure brainwaves. Samsung and Apple's watch-type and ring-type sleep trackers, on the other hand, use photoplethysmography (PPG) sensors to measure heart rate variability (HRV) instead of brainwaves.

    PPG involves projecting LED light onto blood vessels to measure pulse waves. This technology relies on the principle that when blood passes through vessels, the reflection of light changes in response to the expansion and contraction of blood vessels as the heart beats. The green light that comes from the bottom of an Apple Watch or beneath the Oura Ring is the LED light used for this purpose. It's worth noting that along with brainwaves, heart rate variability is the main signal used to measure sleep stages.

    In addition to sleep stages, these sleep trackers also provide information about respiration, oxygen saturation, and snoring. For instance, the Galaxy Watch can detect when the user is asleep and activate the smartphone microphone to monitor snoring. It can also track movements during sleep. The Oura Ring uses motion sensors (actigraphy) to measure body movements and AI to analyze sleep stages, circadian rhythms, and body temperature.

    2. Nearable

    Is there a way to comfortably track your sleep without having to wear a device on your wrist, finger, or ear while you sleep? Nearable sleep trackers are devices designed to meet this need. Examples of nearable sleep trackers include Google Nest Hub, Amazon Halo Rise, and Withings Sleep Tracking Mat. All of them employ a non-contact method, placing the device around the sleeping area for measurement.

    Nearable sleep trackers primarily utilize respiration measurement as their main testing method. Alongside heart rate, respiration patterns provide crucial autonomic nervous system information for tracking sleep stages. During deep sleep stages, breathing tends to be more regular, whereas during light sleep or REM sleep, breathing becomes irregular. Clues like these are essential for monitoring sleep stages through respiration.

    While polysomnography (PSG) measures respiration by wearing a belt around the abdomen, nearable sleep trackers avoid direct attachment to the body. Both Google Nest Hub and Amazon Halo Rise use radar to measure respiration. They shoot radar signals towards the chest and monitor respiration by analyzing the reflected signals.

    These devices also utilize algorithms to analyze sounds like snoring or coughing through their microphone function. Amazon Halo Rise, for instance, gradually brightens the light when it detects movement during sleep or when transitioning into light sleep, aiding in waking up gently.

    Withings Sleep Tracking Mat, while being a nearable device, involves some contact with the body as it is placed beneath the mattress while sleeping. It also relies on signals related to respiration. When you lie on the mattress and breathe, it exerts pressure, which Withings Sleep Mat senses and uses as a signal to detect respiration.

    3. Airable

    A device that is much more convenient to use compared to wearables or nearables in tracking sleep is the Airable sleep tracker. Airable sleep trackers encompass applications equipped with sleep measurement features such as Sleep Routine, SleepScore, Pillow, and Sleep Cycle.

    The Airable sleep tracker can be used effortlessly like the air, anytime and anywhere, as long as you have a smartphone. Unlike nearables, there's no need to carry a specific device separately. The ability for software updates is another significant advantage.

    These sleep trackers mainly rely on a sound-based measurement method, leveraging the excellent microphones already built into smartphones. The information obtained through sound measurement is diverse. For instance, measuring snoring sounds can detect sleep apnea. More importantly, analyzing the regularity of breathing patterns through sound measurement allows monitoring of the autonomic nervous system, a crucial element in tracking sleep stages.

    Sleep Cycle, with over 10 million downloads, provides relatively straightforward tracking results compared to its popularity. It tracks deep and light sleep using sound and presents the results graphically. Pillow app utilizes both sound and accelerometer sensors. Placing your smartphone on the bed while sleeping, the accelerometer reacts to your movements, which, along with sound analysis, contributes to reporting sleep states.

    Sleep Score is an app that uses ultrasound in addition to sound. It employs technology that analyzes the information received when ultrasound sent towards the body reflects back.

    Sleep Routine, on the other hand, employs a slightly different approach from conventional apps that analyze sleep using sound. Rather than merely assessing whether breathing sounds are loud, soft, frequent, or infrequent, it delves into meticulous sound analysis. It precisely analyzes sound signals, such as breathing patterns and tone, crucial bio-signals for tracking sleep stages, with the help of AI. This meticulous analysis method, especially, provides higher resolution tracking of the autonomic nervous system compared to methods that detect movement using actigraphy or radar. As a result, it offers much more accurate results compared to other sleep tracking apps.

    In contrast to other Airable apps that provide numerical results, Sleep Routine breaks down these numbers into easily understandable insights. Alongside summarizing a night's sleep in a single line, it offers simple comments on how to achieve better sleep.

    Which sleep tracker would you prefer? May everyone continue their healthy sleep life with the most suitable sleep tracker that combines convenience and accuracy.

    💡 [Summary] Wearable, Nearable, Airable!

    1. Wearable Sleep Tracker
    This type involves direct attachment to the body, such as watches, rings, earphones, etc., to measure sleep data. It operates on principles like LED lights, motion sensors, brainwaves, and body temperature. One must endure the inconvenience of wearing the device during sleep.

    2. Nearable Sleep Tracker
    These devices are placed around the sleeping area or under the mattress, eliminating the need to wear a device directly. They work by sensing respiration through methods like radar or mattress pressure. Although they offer non-contact advantages, the positioning, angle, and distance from the device can affect measurement results.

    3. Airable Sleep Tracker
    Airable sleep trackers are application-based and can be used anytime, anywhere, with just a smartphone, and are updated through software. They measure sleep using the smartphone's built-in microphone to capture sounds. Unlike wearables and nearables, there's no need to purchase a separate device for sleep tracking.