Pillow's Rem Deep Sleep Tracking: How Does It Work?

Sleep is a complex and mysterious process that occupies about a third of our lives. Sleep occurs in cycles, and there are two main categories: rapid eye movement (REM) sleep and non-REM (NREM) sleep. The latter is further divided into three stages, with N3 being the deepest sleep stage. Deep sleep is crucial for health and well-being, and most adults need around 1.5–2 hours of it per night. Pillow, a sleep tracking app, uses an algorithm based on body mobility and sound input to estimate sleep stages and provide insights into sleep quality. It helps users understand their sleep patterns and make adjustments for better rest.

Pillow uses an algorithm based on body mobility and sound input during sleep

The Pillow app uses an algorithm based on body mobility and sound input during sleep to track REM and deep sleep. The app draws data from the device's sensors, including the accelerometer, gyroscope, and microphone, to register body motions and noise levels during sleep. This raw data sequence is then fed into a probability model to estimate the sleep stage at any given time.

The Pillow app's algorithm is designed to distinguish between the different stages of sleep, which include Non-REM (NREM) and Rapid Eye Movement (REM) sleep. NREM sleep is further divided into three stages: N1, N2, and N3. During N1, the first stage of sleep, the sleeper is between wakefulness and sleep, and muscular and eye activity is present. It is the easiest stage to wake from. In N2, muscular activity slows down significantly, but the sleeper still reacts to environmental stimuli like noises and light. N3, also known as Slow Wave Sleep (SWS) or deep sleep, is characterized by minimal muscular and eye movement, and the sleeper does not react to most external stimuli.

REM sleep, on the other hand, is known as the dream stage, during which brain activity is high, comparable to being awake. It is the most challenging sleep stage to awaken from, and the muscles are completely paralyzed. This muscle paralysis is considered a safety mechanism to prevent violent reactions to vivid dreams. While the precise effects of REM sleep are still being researched, it is believed to play a crucial role in enhancing the brain's ability to learn complex tasks.

The Pillow app utilizes a combination of motion tracking and sound detection to estimate the user's sleep stage at any given moment. The app's algorithm processes data on body movements and sound inputs to determine whether the user is in NREM or REM sleep. Over time, as the user continues to use the app, the algorithm adapts to their personal sleep patterns, resulting in more accurate readings.

In addition to tracking sleep stages, the Pillow app also provides a sleep quality analysis. It takes into account factors such as sleep cycle duration, the percentage of time spent in each sleep stage, disturbances during the night, environmental noises, and the number of awakenings. These parameters are processed using a scientifically backed algorithm to calculate a sleep quality index, presented as a percentage. The overall quality score typically ranges from 25% for a poor sleep to about 90% for excellent sleep.

The Pillow app provides a sleep analysis diagram and a quality score

The Pillow app provides a detailed sleep analysis diagram and a quality score as a percentage. The diagram is based on the universally accepted division of sleep into four stages and two categories: Rapid Eye Movement (REM) and Non-REM (NREM). The three NREM stages are further divided into N1, N2, and N3, with N1 being the lightest stage of sleep and N3 being the deepest. The REM stage is when we dream, and the app uses an algorithm based on body mobility and sound input to estimate the sleep stage at any given time.

The Pillow app's sleep analysis diagram uses a stepped line, or hypnogram, to represent the different stages of sleep. This approach ensures accuracy, as sleep research suggests that transitions between sleep stages can occur instantly. The various stages are colour-coded to make the diagram easy to understand for the average user. The app also provides a quality score for each sleep session, calculated using scientifically accepted sleep quality assessment methods. This score takes into account various factors such as sleep cycle duration, disturbances during the night, environmental noises, and the number of awakenings.

In addition to the sleep analysis diagram and quality score, Pillow offers personalized insights and sleep tips, allowing users to create a unique sleep program tailored to their goals. It also includes features such as audio recordings, sleep trends, mood tracking, and notes to help users understand their sleep patterns and make improvements. The app integrates with Apple Health to provide comparisons between sleep quality and various health metrics.

Pillow's sleep analysis and quality score aim to provide users with valuable insights into their sleep habits, helping them identify areas for improvement and make informed decisions to enhance their sleep quality and overall well-being. The app's comprehensive approach to sleep tracking and analysis offers a useful tool for those seeking to optimize their sleep and understand their sleep patterns on a deeper level.

Deep sleep is when the body repairs and strengthens the immune system

Sleep is divided into four stages and two categories: rapid eye movement (REM) and non-REM (NREM). The third stage of sleep, N3 (NREM), is also known as slow-wave sleep (SWS) or deep sleep. During this stage, there is practically no muscular and eye movement, and the person is not reacting to most environmental stimuli.

Secondly, during sleep, the body produces proteins called cytokines that target infection and inflammation, creating an immune response. Sleep also promotes the production of T-cells, which are white blood cells that play a critical role in the body's immune response to infectious diseases.

Additionally, the inflammatory response that occurs during sleep may aid in recovery, fortifying the immune system as the body works to repair wounds or fight off infections. This inflammatory response is driven by both sleep and the body's circadian rhythm or internal clock.

Finally, deep sleep may also strengthen the immune system by reinforcing the immune system's ability to recognise and react to dangerous antigens. This immune memory is essential for the body to effectively identify and respond to potential threats.

Overall, deep sleep plays a crucial role in the body's ability to repair and strengthen its immune system, helping to maintain overall health and well-being.

REM sleep is important for dreaming and processing emotions

REM sleep, or rapid eye movement sleep, is the fourth and final stage of sleep. It is characterised by relaxed muscles, quick eye movement, irregular breathing, elevated heart rate, and increased brain activity. During REM sleep, the brain's activity is similar to its activity when a person is awake.

REM sleep is important for dreaming. A majority of dreams occur during this sleep stage. Dreams during REM sleep are usually more vivid and fantastical than those during non-REM sleep. The first period of REM sleep typically lasts about 10 minutes, with each subsequent REM stage getting longer. The final one may last up to an hour.

REM sleep is also important for processing emotions. The amygdala, the part of the brain that processes emotions, activates during REM sleep. Dreams, which are more vivid during REM sleep, may be involved in emotional processing.

REM sleep makes up about 20% of total sleep time for adults. Most adults need about two hours of it each night.

Sleep efficiency depends on a variety of factors including sleep time

Sleep efficiency depends on a multitude of factors, not just the number of hours clocked in bed. The Pillow app is designed to help users understand their sleep habits by tracking their sleep cycles and providing a detailed analysis of their sleep stages. It also offers personalised insights and tips to help users optimise their sleep.

Sleep can be divided into four stages and two categories, namely Rapid Eye Movement (REM) and Non-REM (NREM). The stages are N1 (NREM), N2 (NREM), N3 (NREM), and REM. During the N1 stage, a person is between wakefulness and sleep, and it is the easiest stage to wake from. In the N2 stage, the person becomes harder to wake, and muscular activity slows down significantly. The N3 stage is also known as Slow Wave Sleep (SWS) or deep sleep, where there is practically no muscular and eye movement, and the person does not react to most environmental stimuli. Finally, the REM stage is when the person is in a state of high brain activity, similar to being awake, and it is the hardest sleep stage to wake from. The muscles are completely paralysed during this stage, possibly as a safety mechanism to prevent the sleeper from reacting violently to vivid dreams.

A typical sleep cycle for adults progresses in the following order: N1, N2, N3, N2, REM, and lasts for about 90 to 110 minutes. A person will go through four to five sleep cycles per night, with deep sleep occupying the first few hours after falling asleep, and REM sleep increasing towards the end of the cycles before natural awakening. An adult without sleep disorders is expected to spend about 20% of their sleep time in the REM stage.

The Pillow app uses an algorithm based on body mobility and sound input during sleep, which is drawn from the device's sensors. This raw data is then processed through a probability model to estimate the sleep stage at any given time. The app also provides a visual representation of the user's sleep analysis in the form of a hypnogram, which is a stepped line that reflects the instantaneous transitions between sleep stages. Additionally, the app assigns a quality score to each sleep session as a percentage, taking into account various factors such as sleep cycle duration, disturbances, environmental noises, and the number of awakenings.

While the amount of sleep needed varies from person to person, the Centers for Disease Control and Prevention (CDC) recommends that adults aged 18–60 aim for at least 7 hours of sleep per night, with approximately 25% of that time spent in deep sleep. However, as people age, the amount of deep sleep needed decreases, and they spend more time in the N2 stage.

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