Sleep Apps: Tracking Rem, How Does It Work?

Sleep-tracking apps have become increasingly popular, with many people wanting to gain insight into their sleep patterns and habits. These apps can help users understand how much sleep they are getting and how much deep sleep they need. While the technology behind these apps is complex, they generally use motion detection, sound analysis, and heart rate measurements to track sleep. Some apps use the phone's built-in accelerometer to measure movement during sleep, while others use the microphone and speaker to judge sleep quality. Wearable devices, such as smartwatches and rings, can also be used in conjunction with sleep-tracking apps to provide additional data such as heart rate and movement. These apps can offer valuable insights to help users improve their sleep habits and overall health.

Heart rate and respiration rate

Sleep tracking devices are a popular way to monitor sleep patterns and quality. While they cannot measure sleep directly, they can estimate sleep by tracking inactivity and movement. Some sleep trackers are wearable devices that you strap to your wrist or finger, while others are non-wearable and are placed on your mattress or bedside table.

Sleep tracking devices use a variety of technologies to track heart rate and respiration rate. Here are some common methods:

• Optical Heart-Rate Monitoring: This technology is used in fitness trackers, the Apple Watch, and the Oura Ring. It uses tiny LEDs in the band to shine a light through your skin and capture blood flow. As your heart rate changes, so does the light reflected back to the device. This information is combined with movement data to deliver a sleep report.
• Accelerometer: This technology is more commonly used in fitness trackers and other wearables than in phone apps. It interprets stillness as sleep and movement as wakefulness. However, it may not be very accurate when used alone, as it can perceive someone as asleep when they are merely lying still.
• Sound Detection: Phone apps that use sound detection technology analyze the sounds of various movements during different sleep stages. When the app detects less movement, it assumes you are in deep sleep, and when it detects more movement, it assumes you are in light sleep.
• Sonar: Sonar technology uses sound waves to track sleep. The phone's microphone picks up the sound waves deflected off your chest as you breathe, as the rhythm and depth of your breath change during different sleep stages. If your phone is compatible with a sonar-enabled app, it should be placed on a nightstand close to the height of your chest.
• Ballistocardiography: This technology is used in non-wearable sleep trackers that lay on top of your mattress. It detects movement, heart rate, and respiration by analyzing micro-movement data from the tracker's sensors.

By tracking heart rate and respiration rate, sleep trackers can provide insights into your sleep metrics, including sleep staging, sleep efficiency, and restfulness. This information can help you improve your sleep habits and overall health.

Accelerometers and motion detection

Accelerometers are small motion detectors that measure how much movement you make while you sleep. This data is then analysed using an algorithm to estimate sleep time and quality. Sleep trackers that use accelerometers include the Apple Watch, the Biostrap Kairos, the Muse S Gen 2 Headband, and the Oura. The Apple Watch, for example, uses the accelerometer in combination with a heart rate sensor to break down sleep into four stages: awake, REM, light, and deep sleep. The Oura ring uses an accelerometer to track total sleep, time in bed, sleep efficiency, and resting heart rate.

Sleep-tracking apps that use accelerometers include Sleep.com, which uses the phone's inbound accelerometer to detect movement patterns and determine whether the user is in deep or light sleep. The app also uses sonar technology to measure movement and breathing rate, providing an accurate picture of the user's sleep.

While accelerometers can provide insights into sleep time and quality, they have limitations in measuring sleep stages. According to the Sleep Foundation, there is little difference in movement between the various sleep stages, so accelerometers alone cannot accurately measure them. Therefore, sleep trackers that only offer an accelerometer may not be the best fit for those seeking more detailed information about their sleep stages.

Sound analysis

Some apps, like Sleep Cycle, rely solely on sound analysis to track sleep. Sleep Cycle uses a phone's microphone to detect the sounds made when the user moves during sleep. It does not depend on sound waves deflecting off the user's chest, so the phone can be placed on a nightstand rather than requiring precise placement. However, this method can lead to errors if the app picks up other sounds in the room.

Other apps, like SleepWatch, combine sound analysis with data from wearable devices such as the Apple Watch. SleepWatch automatically collects data on sleep duration, quality, and variations in heart rate by integrating with the Apple Watch. It also provides a sleep score and in-depth analysis based on the user's sleep patterns.

Additionally, some apps offer sound-based features beyond sleep tracking. For example, the Philips Sleep Headphones with Kokoon combine earbuds with sleep tracking and provide meditations, soothing sounds, and sleep stories to aid sleep. Similarly, the Google Nest Hub 2nd Gen uses a microphone to track snoring and sleep talking but also offers a range of sleep sounds and podcasts to help users fall asleep.

While sound analysis is a widely used method for sleep tracking, it is important to note that these apps do not directly measure sleep. They estimate sleep patterns based on detected sounds and inactivity. For more precise data, a medical sleep study that monitors brain waves is necessary.

Wearable devices

Wearable sleep-tracking devices are available in the form of rings, wristbands, and smartwatches. These devices tend to be lightweight and can collect health data throughout the day, not just during sleep. They can track sleep duration by measuring the time the user is inactive, as well as sleep quality by detecting interrupted sleep. Some devices can also track sleep phases and time alarms to go off during periods of lighter sleep, making it easier for the user to wake up.

Wearable sleep trackers collect a combination of measurements, including heart rate and heart rate variability, movement, breaths per minute, and skin temperature. They use algorithms to estimate sleep cycles and provide insights into sleep patterns. Examples of popular wearable sleep trackers include the Apple Watch Series 9, Google Pixel Watch 2, Fitbit, Ultrahuman Ring Air, and Whoop 4.0. These devices can sync with apps such as Fitbit Premium and Google Health to provide additional insights and long-term sleep trends.

While wearable sleep trackers can provide valuable information, they have some limitations. They do not directly measure sleep but rather estimate it through inactivity and other metrics. For more precise data, a medical sleep study that monitors brain waves is necessary. Additionally, some users may find wearing a device to bed uncomfortable or inconvenient, especially if it requires frequent charging.

Sleep quantity and quality

Sleep is essential for good health. Lack of sleep can make you feel groggy and distracted and expose you to potential sleep-related diseases. Sleep tracking apps are a great way to monitor your sleep quantity and quality and help you take control of your sleep.

Sleep tracking is still a relatively new area, with tech companies experimenting with various devices and apps to help you detect health problems and find solutions. There are several ways to track your sleep, from wearable devices to apps that use motion detection and microphones. These devices monitor everything from your heart rate and oxygen consumption to the number of steps you take each day, giving you a detailed picture of your sleep behaviour and sleep cycles.

Most sleep trackers measure sleep quantity and quality by using accelerometers, small motion detectors. Accelerometers measure how much movement you make while you sleep. This data is then analysed using an algorithm to estimate sleep time and quality. Some trackers also use sound analysis to identify sleep states, although this can lead to errors if other sounds are picked up in the room. Some apps, like SleepWatch, integrate with wearable devices like the Apple Watch to automatically collect data on your sleep, including heart rate and movement, without the need to remember to start the app.

While sleep tracking apps can be a helpful tool, it's important to remember that they don't directly measure sleep. Instead, they often measure inactivity as a way to estimate sleep. If you want exact data about your sleep habits, a medical sleep study that monitors brain waves is necessary. However, tracking devices can help you recognize patterns in your sleep habits and make adjustments to improve your sleep quality and quantity. For example, if you notice you sleep better on days you exercise, you can prioritize working out. Additionally, some apps provide a "sleep score" and a "readiness score" to help you set realistic goals and choose appropriate workouts for the day.

If you're concerned about your sleep quality, it's always a good idea to talk to a health practitioner.

Frequently asked questions