Fitbit Sleep Tracking: How Does It Work?

Sleep is an essential component of health and well-being, impacting everything from a person's daily mood to their appetite, physical activity, and more. Fitbit offers advanced sleep tools to help users track their sleep and get better rest. The Fitbit device uses an accelerometer, heart rate sensors, and motion detectors to track sleep. It infers when a user is sleeping and what stage of sleep they are in by measuring bodily accelerations of the wrist and heart rate. It also offers a daily sleep score breakdown and personalized guidance to help users improve their sleep habits.

Fitbit uses an accelerometer and optical photoplethysmography to track sleep

Fitbit uses an accelerometer and optical photoplethysmography (PPG) to track sleep. The accelerometer is a device that measures bodily accelerations of the wrist. This is used in conjunction with PPG, which measures blood flow based on how green light from an LED on the back of the watch is reflected by the body. This allows the Fitbit to infer when you are sleeping and what stage of sleep you are in.

The Fitbit uses your movement and heart rate patterns to estimate your sleep stages. When you haven't moved for about an hour, the Fitbit assumes you're asleep. It also tracks the 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 stages.

The Fitbit Sleep Score is a quick way to gauge your sleep, and it is based on heart rate, the time spent awake or restless, and sleep stages. The overall sleep score is a sum of individual scores in three components: sleep duration, sleep quality, and restoration. The restoration component includes estimated oxygen variation, which can indicate variations or disturbances in breathing during sleep.

Fitbit also offers a snore and noise detection feature that allows the microphone on the device to track noise while you sleep. By analyzing noise information every few seconds, the device can track the overall noise level of your surroundings and check for snoring throughout the night. This feature is available with a Premium subscription.

To accurately track your sleep with a Fitbit, it is recommended to wear the device higher on your wrist, about 2-3 finger widths above the wrist bone. The band should be secure but not too tight.

It measures heart rate, movement and sleep patterns

Fitbit uses a combination of heart rate, movement and sleep pattern measurements to track your sleep. The Fitbit watch infers when you're sleeping and what stage of sleep you're in by using an accelerometer, which measures bodily accelerations of the wrist, and 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.

When you don't move for about an hour, your Fitbit 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), which 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.

Your Fitbit device can also track your sleep patterns and help you notice variations. Your sleep stages data is useful for tracking patterns and noticing variations. If you have any concerns about your sleep health, it is recommended that you share this information with your doctor.

The Fitbit Sleep Score is a quick way to gauge your sleep. It is based on heart rate, the time spent awake or restless, and sleep stages. The overall sleep score is a sum of your individual scores using three components: sleep duration, sleep quality, and restoration, for a total score of up to 100. Most Fitbit users get a sleep score between 72 and 83.

Fitbit Premium offers several tools that can help you improve your sleep habits and receive personalized guidance. These include a daily sleep score breakdown and guided programs developed with sleep experts, such as "Habits for Restful Sleep" and "Get More Sleep".

It can track your sleep stages, including light sleep, deep sleep and REM sleep

Sleep is divided into two types: rapid-eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. NREM sleep is further divided into light sleep and deep sleep. REM sleep is associated with vivid dreams and longer periods of REM sleep usually occur later in the night.

Fitbit estimates sleep stages by using 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), which fluctuate as you transition between light sleep, deep sleep, and REM sleep stages.

The Fitbit Versa infers when you’re sleeping and what stage of sleep you’re in using an accelerometer (an instrument for measuring bodily accelerations of the wrist) coupled with a technique called optical photoplethysmography, or PPG. PPG measures blood flow based on how green light from an LED on the back of the watch is reflected by the body.

According to a paper published by Fitbit scientists in 2017, the watch's sensors can classify sleep stages with 69% accuracy in any given 30-second time window. However, it's important to note that Fitbit does not measure brainwaves, so it cannot definitively distinguish deep sleep. While it can provide valuable insights into your sleep patterns, it should not be used for medical diagnosis.

It offers a daily sleep score breakdown and personalised guidance

Fitbit Premium offers a comprehensive suite of tools to help you optimise your sleep. One of its key features is the daily sleep score breakdown, which provides a detailed analysis of your sleep patterns and quality. This breakdown is based on several factors, including your heart rate, time spent in each sleep stage, and periods of restlessness or wakefulness. Fitbit's sleep stages are classified as light sleep, deep sleep, and REM sleep, with each serving a unique purpose in your overall sleep cycle. Light sleep is the entry point into sleep, allowing your body to unwind and slow down. Deep sleep typically occurs earlier in the night, while REM sleep, associated with vivid dreams, becomes more prevalent towards the end of the night.

The sleep score breakdown also takes into account the duration of your sleep, the quality of your sleep, and your restoration. Restoration is an important metric that considers the variations in your blood oxygen saturation levels, which can indicate disturbances in breathing during sleep. By tracking your blood oxygen levels, Fitbit can provide insights into potential breathing issues that may impact your sleep quality. This information can be particularly useful for identifying conditions such as Obstructive Sleep Apnea (OSA), which is characterised by fatigue, high blood pressure, and poor eating habits.

In addition to the sleep score breakdown, Fitbit Premium offers personalised guidance to help you improve your sleep habits. This guidance is provided through programs developed in collaboration with sleep experts. One such program, "Habits for Restful Sleep", focuses on building better daytime habits to promote deeper sleep at night. Another program, "Get More Sleep", assists you in refining your nighttime routine and working towards longer, more restorative sleep. These programs offer practical strategies, relaxation techniques, and goals to enhance your sleep quality.

Fitbit's sleep tracking technology utilises motion detectors and heart rate sensors to monitor your sleep. It can infer when you're sleeping and what stage of sleep you're in by measuring your wrist's bodily accelerations and using optical photoplethysmography (PPG) to measure blood flow. This data is then used to generate your personalised sleep score. Fitbit's sleep researchers and the National Sleep Foundation have collaborated to define the sleep stages and provide insights into your sleep patterns.

The sleep tracking feature on Fitbit also includes a Smart Wake function, which allows you to set a silent alarm to wake you up during the optimal stage of sleep. This helps you feel more rested and refreshed when you wake up. Additionally, Fitbit provides a monthly personalised analysis of 10 key sleep metrics, helping you to better understand your sleep habits and make informed adjustments.

It can also track noise and snoring

The microphone on your Fitbit can be used to track noise and snoring. This feature is called "snore and noise detection", and it is available on the Fitbit Sense and Fitbit Versa 3. The device analyses noise information every few seconds to track the overall noise level of your surroundings and check for snoring throughout the night. When you wake up, you can find a summary of your nightly results in a report.

To turn on snore and noise detection, open the Fitbit app and tap the "Sleep duration" tile on the "Today" tab. Then, tap the menu icon in the top right corner and select "Settings". Finally, turn on "Snore & noise detect" and follow the on-screen instructions. It is important to note that if there is too much background noise, the device's microphone may not be able to pick up snoring accurately. Therefore, it is recommended to avoid playing white noise or other ambient sounds during sleep when using this feature.

The snore and noise detection feature can be useful for tracking your sleep patterns and noticing any variations. For example, if you have concerns about sleep apnea or other sleep disorders, the data provided by this feature can be shared with your doctor for further analysis and guidance. It is worth mentioning that the sleep stages data provided by Fitbit should not be used for diagnosing or treating any medical conditions, and users are advised to consult a healthcare professional for specific questions or concerns regarding their health and sleep.

In conclusion, the snore and noise detection feature on Fitbit Sense and Fitbit Versa 3 devices offers valuable insights into your sleep environment and snoring habits. By analysing noise levels and detecting snoring, the device provides a comprehensive summary of your nightly results. This information can help you better understand your sleep patterns and make informed decisions to improve your sleep quality.

Frequently asked questions