Fitbit's Sleep Tracking: Understanding Your Deep Sleep And Rem

Fitbit devices with heart-rate tracking can monitor your sleep by estimating sleep stages using a combination of movement and heart-rate patterns. When you haven't moved for about an hour, the device assumes you're asleep. It also takes into account the length of time you display movements indicative of sleep, such as rolling over. While you sleep, the device tracks beat-to-beat changes in your heart rate, known as heart rate variability (HRV), which fluctuate as you transition between light sleep, deep sleep, and REM sleep. In the morning, when you sync your device, it uses movement and heart rate patterns to estimate your sleep cycles from the previous night.

Fitbit estimates sleep stages by using movement and heart-rate patterns

Fitbit devices with heart-rate tracking can estimate sleep stages by using movement and heart-rate patterns. When the device detects that you have not moved for about an hour, it assumes that you are asleep. Additional data, such as the length of time of movements that indicate sleep behaviour (e.g. rolling over), can also help confirm that you are asleep.

While you sleep, the device tracks the beat-to-beat changes in your heart rate, known as heart rate variability (HRV). These numbers fluctuate as you transition between light sleep, deep sleep, and REM sleep stages. When you sync your device in the morning, it uses movement and heart rate patterns to estimate your sleep cycles from the previous night.

Fitbit's Sleep Stages feature uses accelerometer data, heart rate variability, and algorithms to estimate how long you spend in each sleep stage. The R&D team at Fitbit conducted extensive internal testing by observing and analysing several hundred nights of heart rate and movement data from volunteer sleepers, while simultaneously characterising their sleep with gold-standard lab equipment.

Fitbit's sleep tracking features use advanced signal processing and machine learning algorithms to track total time slept, as well as identify trends in restlessness and the amount of time people are awake during a sleep period. These algorithms also review night motion patterns and the level of Fitbit users' restlessness.

Fitbit trackers and watches use your sleeping heart rate, movement and more to measure your time spent in each sleep stage and give you a personalised Sleep Score that shows how well you slept.

Fitbit uses an accelerometer to infer when you're sleeping and what stage of sleep you're in

Fitbit devices use an accelerometer to infer when you're sleeping and what stage of sleep you're in. This accelerometer is an instrument for measuring bodily accelerations of the wrist. It is coupled with a technique called optical photoplethysmography (PPG), which measures blood flow based on how green light from an LED on the back of the watch is reflected by the body.

Fitbit's sleep tracking features use advanced signal processing and machine learning algorithms to track total time slept, as well as identify trends in restlessness and the amount of time people are awake during a sleep period. These algorithms also review night motion patterns of being asleep and the level of Fitbit users' restlessness.

When you haven't moved for about an hour, your Fitbit tracker or smartwatch assumes that you're asleep. Additional data, such as the length of time of movements that are indicative of sleep behaviour (such as rolling over), can also help confirm that you're asleep.

While you're sleeping, your Fitbit device tracks the beat-to-beat changes in your heart rate, known as heart rate variability (HRV). These numbers fluctuate as you transition between light sleep, deep sleep, and REM sleep stages. When you sync your device in the morning, Fitbit uses movement and heart rate patterns to estimate sleep cycles from the previous night.

Fitbit looks at how much you're moving and how often your heart is beating to infer whether you're awake, in a deep sleep, a light slumber, or dreaming.

Fitbit devices with heart-rate tracking can record the sleep stages you cycle through

Fitbit estimates your sleep stages by using your movement and heart-rate patterns. When you don't move for about an hour, your tracker or watch assumes you're asleep. Additional data, such as the length of time when your movements indicate sleep behaviour (like rolling over), help confirm your sleep status.

While you sleep, your device tracks the beat-to-beat changes in your heart rate, known as heart rate variability (HRV). These numbers fluctuate as you transition between light sleep, deep sleep, and REM sleep stages. When you sync your device in the morning, it uses your movement and heart rate patterns to estimate your sleep cycles from the previous night.

Fitbit's sleep researchers and the National Sleep Foundation describe the following sleep stages:

• Light sleep: This stage serves as your entry point into sleep each night as your body unwinds and slows down. Your breathing and heart rate usually decrease slightly during this stage. Light sleep promotes mental and physical recovery.
• Deep sleep: This stage typically occurs in the first few hours of sleep. When you wake up feeling refreshed, you likely experienced solid periods of deep sleep the night before. During deep sleep, your body becomes less responsive to outside stimuli, and your breathing, muscles, and heart rate slow down. Deep sleep promotes physical recovery and supports aspects of memory, learning, and your immune system.
• REM sleep: The first phase of REM sleep typically occurs after the initial stage of deep sleep. You generally spend a longer period in REM sleep during the sleep cycles in the second half of the night. During this final stage of sleep, your brain becomes more active, and dreams mainly occur. Your heart rate increases, and your breathing becomes more irregular. REM sleep has been shown to play an important role in mood regulation, learning, and memory.

To get an accurate reading, it's recommended to wear your Fitbit device higher on your wrist (about 2-3 finger widths above your wrist bone). The band should feel secure but not too tight. Additionally, it's important to note that Fitbit devices require at least 3 hours of sleep data to estimate your sleep stages.

Fitbit's sleep researchers describe the sleep stages as light sleep, deep sleep, and REM sleep

Sleep is an essential component of health, playing a role in metabolic and emotional regulation, performance, and memory. Fitbit's sleep researchers and the National Sleep Foundation describe the sleep stages as light sleep, deep sleep, and REM sleep.

Light sleep serves as the entry point into sleep each night as the body unwinds and slows down. During this stage, the breathing and heart rate usually decrease slightly. Light sleep promotes mental and physical recovery, strengthening memory and learning.

Deep sleep typically occurs in the first few hours of sleep. During this stage, the body becomes less responsive to outside stimuli, and the breathing, heart rate, and muscles relax. Deep sleep promotes physical recovery and supports aspects of memory and learning, as well as the immune system.

REM sleep is associated with vivid dreams and typically occurs longer as the night goes on. During this stage, the brain becomes more active, and the heart rate and breathing become more irregular. REM sleep is important for mood regulation, learning, and memory consolidation.

Fitbit devices with heart-rate tracking can estimate these sleep stages by using movement and heart-rate patterns. They track the beat-to-beat changes in heart rate, known as heart rate variability (HRV), which fluctuate as the wearer transitions between the different sleep stages. While light sleep, deep sleep, and REM sleep are the main stages, Fitbit also tracks the time spent awake, initially categorising it as 'restless' before combining it with actual awake time to give total awake minutes.

Fitbit's sleep tracking features use advanced signal processing and machine learning algorithms to track total time slept

Fitbit's sleep-tracking features are enabled by advanced signal processing and machine learning algorithms. These algorithms are able to track the total time slept, as well as identify trends in restlessness and the amount of time people are awake during a sleep period.

The Fitbit device can estimate sleep stages by using movement and heart-rate patterns. When the device senses that you haven't moved for about an hour, it assumes that you're asleep. Additional data, such as the length of time of movements that are indicative of sleep behaviour (such as rolling over), can also help confirm that you're asleep.

While you sleep, the device tracks the beat-to-beat changes in your heart rate, known as heart rate variability (HRV). These numbers fluctuate as you transition between light sleep, deep sleep, and REM sleep stages. When you sync your device in the morning, Fitbit uses movement and heart rate patterns to estimate sleep cycles from the previous night.

The Sleep Stages feature uses accelerometer data, heart rate variability (the changes in time between beats) and algorithms to more accurately estimate how long you spend in light, deep and REM sleep stages (as well as time awake) each night. The R&D team at Fitbit conducted extensive internal testing by observing and analysing several hundred nights of heart rate and movement data from volunteer sleepers, while simultaneously characterising their sleep with gold-standard lab equipment when first implementing these features.

Frequently asked questions