Introduction to sleep monitoring principles of HUAWEI smart wearables
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| Introduction to sleep monitoring principles of HUAWEI smart wearables |
What is sleep and what are its functions?
Sleep is a natural physiological state that occurs repeatedly. It happens in certain periods of time every day, various conscious active behaviors disappear, and the response to external environment stimulation is weakened.
Sleep plays an important role in physiological functions, including restoring physical strength, consolidating memory, regulating emotions, enhancing immunity, and maintaining endocrine balance.
Sleep architecture and sleep cycle
Sleep is categorized into rapid eye movement (REM) and non-REM (NREM) sleep, the latter of which is further subdivided into light and deep sleep stages.
In a sleep process, REM sleep and NREM sleep occur alternately, and the alternate occurrence is referred to as a sleep cycle. A normal person usually experiences 4 to 6 sleep cycles throughout the night, with each cycle lasting approximately 90 to 100 minutes. In a typical sleep cycle, the stages usually progress in the following order: Wakefulness → Light sleep → Deep sleep → Light sleep → REM sleep.
However, each cycle is not a simple repetition of the previous one. Generally, deep sleep occurs mostly in the first half of the sleep period, while REM sleep occurs mostly in the second half. An individual may not experience all sleep stages, and the stages may not progress regularly. For example, a user may directly go from light sleep, deep sleep, or REM sleep to the wakefulness stage.
Functions of each sleep stage
Sleep is classified into REM sleep and non-REM (NREM) sleep, and NREM sleep further includes N1/N2 (light sleep) and N3 (deep sleep). The sleep effects at each stage are as follows:
|
Sleep Stage |
Function |
|---|---|
|
Rapid eye movement (REM) sleep |
REM sleep is characterized by rapid eye movements under the eyelids. Most people woken during this stage report they are dreaming. Muscles are generally relaxed in this stage, and this is due to a safety mechanism to prevent acting out in dreams. This stage plays a key role in consolidating memories and stabilizing emotions. |
|
Light sleep (N1/N2) |
N1/N2 is categorized as light sleep. In this stage, EEG activity slows in tandem with the heart rate and respiration rate, while body temperature begins to decline. Although in a state of sleep, people can be easily aroused. Light sleep is a normal physiological need and is just as important as other sleep stages. However, if light sleep accounts for a high proportion of the total sleep time, sleep quality will deteriorate, leading to tiredness and fatigue. |
|
Deep sleep (N3) |
During N3 (deep sleep), brain wave frequency decreases significantly, as do respiratory rate and blood pressure. This stage of sleep is the hardest to wake from. Awakening during deep sleep can lead to dizziness, palpitations, and irritability. Research shows that deep sleep enables the brain to rest fully, aiding in recovery from fatigue and playing a vital role in maintaining emotional health and a positive mindset. Generally speaking, longer durations of deep sleep correlate with better sleep quality. |
Gold standard for sleep monitoring
Polysomnography (PSG) is the gold criterion for sleep monitoring. It captures over ten categories of physiological data, including EEG, ECG, EMG, and SpO2, via sensors on the head, chest, and limbs, providing an accurate analysis of sleep stages and health conditions.
PSG typically requires an overnight stay in a specialized sleep monitoring room at a hospital. Before sleep, healthcare professionals will attach multiple sensors to your body to collect various health data, with a professional technician monitoring and recording the entire process. After sleep monitoring is complete, the professional physician will systematically interpret the data and analyze the sleep quality and possible sleep issues (such as insomnia, sleep apnea, and narcolepsy).
Evolution of HUAWEI TruSleep™
Phase 1: Normal sleep (2015–2017)
Early sleep monitoring technologies were limited by sensors. They relied solely on accelerometer (ACC) sensors to collect body activity signals and roughly distinguished between sleep and wakefulness based on the frequency and amplitude of body movements, making it impossible to implement sleep staging.
Phase 2: HUAWEI TruSleep™1.0–4.0 (2017–2025)
HUAWEI TruSleep™ 1.0–4.0 applied the cyclic alternating pattern (CAP) standard and utilized CPC technology to evaluate sleep stability based on heart rate and respiratory coherence. By extracting motion and physiological features from its sensors, they achieved automatic sleep staging (wakefulness, light sleep, deep sleep, and REM sleep) and provides sleep timing and scoring features, offering a comprehensive and objective insight into sleep health.
Phase 3: HUAWEI TruSleep™ 5.0 (2026–)
As technology continues to advance, the sleep staging standard developed by the American Academy of Sleep Medicine (AASM) have formed a comprehensive training and application system, which is widely used in the industry. The AASM technology distinguishes sleep stages based on the proportion of slow-wave intensity and frequency in brain waves, reflecting the relaxation state of brain nerves. In recent years, the medical community has gradually recognized the identification of sleep stages (N3 (deep sleep), N1/N2 (light sleep), and REM (rapid eye movement)) based on the frequency of brain waves.
HUAWEI TruSleep™ 5.0 uses sensors to obtain characteristics such as the heart rate interval, frequency domain, time domain, and body movement, and extract characteristics including physical activity, body posture, heart rate, respiration, and neural activity, compares the sleep stage results with the AASM criteria, and identify the macro architecture during sleep, including N3 (deep sleep), N1/N2 (light sleep), and REM (rapid eye movement). In this way, sleep cycle changes can be better presented and sleep quality can be evaluated.
Changes in HUAWEI TruSleep™ 5.0
- Improved sleep staging mode
HUAWEI TruSleep™ 4.0 and earlier versions use sensors to extract physical activity, heart rate, and respiration data to determine sleep stages, which can objectively reflect your sleep health. HUAWEI TruSleep™ 5.0 uses sensors to obtain characteristics such as the heart rate interval, frequency domain, time domain, and body movement, and extract characteristics including physical activity, body posture, heart rate, respiration, and neural activity, and compares the sleep stage results with the AASM criteria. It presents sleep quality more comprehensively from two dimensions: sleep structure and sleep stability.
Due to the new upgrade of the sleep staging algorithm, the duration or proportion of N3 (deep sleep) may change. However, as long as the proportion is within the reference value range, N3 (deep sleep) is normal.
- More reasonable sleep stage architecture
The sleep structure includes N3 (deep sleep), N1/N2 (light sleep), and REM, which are dynamically cycled. This reflects the intrinsic rhythmicity of physiological and neural activity. The clearer sleep structure allows you to understand your sleep quality with great ease.
- New indicator: stable sleep
Stable sleep features high coordination between respiration and heart rate. It exists in both N3 (deep sleep) and N1/N2 (light sleep). It serves as a key indicator of physical recovery and provides an objective assessment of overall sleep health, offering an empirical basis for lifestyle and physical adjustments.