How Fitbit Flex Tracks Your Sleep

Fitbit devices are well-known for their ability to track sleep. The Fitbit Flex can automatically detect when you're sleeping and logs your sleep for you. This is done through movement, as the device assumes you're asleep when you haven't moved for about an hour. Fitbit devices with heart rate monitors can also track sleep stages, differentiating between light sleep, deep sleep, and REM sleep. The data collected by Fitbit devices can help users understand their sleep patterns and make adjustments to improve their sleep quality.

Fitbit Flex auto-sleep tracking

The auto-sleep tracking feature works by detecting when your body is completely at rest and you haven't moved for about an hour. It then records that you're asleep. If your Fitbit device tracks your heart rate, it can also track your sleep stages, including light sleep, deep sleep, and REM sleep. If your device doesn't track your heart rate, it can still track your sleep patterns, including the time spent awake, restless, and asleep.

In addition to the auto-sleep tracking feature, Fitbit also offers a Sleep Profile feature, which provides a more detailed breakdown of your sleep. This feature is available only on specific models, including the Charge 5, Charge 6, Inspire 2, Inspire 3, or Luxe tracker, or any Sense or Versa watch (except the original 2018 model). To access the Sleep Profile feature, you need a Fitbit Premium subscription.

The Fitbit app also allows you to edit or delete your sleep logs. You can access these features by going to the Sleep Duration tile on the Today tab and tapping the menu icon. From there, you can choose the sleep session you want to edit or delete.

Heart rate and sleep stages

Fitbit devices with heart rate monitors can track sleep stages and discern between light sleep, deep sleep, and REM sleep. REM sleep is when vivid dreams are more likely. Fitbit's sleep researchers and the National Sleep Foundation describe the following sleep stages: Light sleep, which serves as the entry point into sleep each night as the body unwinds and slows down; Deep sleep, which is when the brain exhibits less activity than in REM sleep; and REM sleep, which is when the eyes move quickly in different directions, the heart rate increases, and the breathing becomes more irregular. Dreams mainly occur during REM sleep, and it has been shown to play an important role in mood regulation, learning, and memory.

Fitbit devices that track heart rate (except Charge HR and Surge) also track sleep stages. Fitbit estimates sleep stages by using movement and heart rate patterns. When the user hasn't moved for about an hour, the tracker or watch assumes they are asleep. Additional data, such as the length of time when movements indicate sleep behaviour (like rolling over), help confirm the sleep status. While the user sleeps, the device tracks the beat-to-beat changes in their heart rate, known as heart rate variability (HRV), which fluctuates as the user transitions between light sleep, deep sleep, and REM sleep stages. When the user syncs their device in the morning, it uses their movement and heart rate patterns to estimate their sleep cycles from the previous night.

The Sleep Profile feature, which provides a more detailed breakdown of the user's sleep, is available only on specific models. To get these reports, the user will need a Charge 5, Charge 6, Inspire 2, Inspire 3, or Luxe tracker, or any Sense or Versa watch (except the first Versa model from 2018). Google Pixel watches can also track sleep. The user can also see their sleep score on their Fitbit by swiping up from the clock face to see their daily stats. This score reflects the quality of their sleep based on their heart rate, the time spent asleep or restless, and their sleep stages.

The user can also purchase a Fitbit Premium subscription to access more detailed information about their sleeping heart rate and sleep stages. This includes a detailed breakdown of their restoration score, which is based on their sleeping and resting heart rates and how much time they spent tossing and turning. They will receive a higher restoration score when their sleeping heart rate is lower than their daytime resting heart rate.

Sleep score and sleep quality

The Fitbit Flex can automatically recognize when you’re sleeping and logs your sleep for you. This is done by tracking your sleep through movement. When your body is completely at rest and you haven't moved for about an hour, your Fitbit Flex will record that you're asleep.

The Fitbit app will display a sleep score on the homepage, which is a rating out of 100 reflecting the quality of your sleep. This score is based on your heart rate, the time spent asleep or restless, and your sleep stages (if your Fitbit has been able to collect enough good quality data). If you don't have a sleep score, it's because your device hasn't gathered enough high-quality data. This could be due to your watch being fastened too loosely or because you were lying in a way that restricted blood flow.

If you have a Fitbit Premium subscription, you can access more detailed information about your sleep. This includes a more comprehensive breakdown of your sleep as well as personalized insights and recommendations about how to improve your sleep routine. You can also compare your sleep patterns with your baseline or typical values for people of your age and gender. Additionally, with a Premium subscription, you can turn on the snore and noise detection feature to allow the microphone on your Fitbit to track noise, including snoring from you or someone next to you.

Fitbit devices with heart rate monitors can also discern between different sleep stages, such as light sleep, deep sleep, and REM sleep. This is done by tracking the beat-to-beat changes in your heart rate, known as heart rate variability (HRV), which fluctuate as you transition between different sleep stages.

Snore and noise detection

The Snore and Noise Detect feature is available on the Fitbit Sense and Fitbit Versa 3 smartwatches. This feature requires a Fitbit Premium subscription. The microphone on the watch collects information about the noise in your environment every few seconds once the tracker has determined you are asleep. It will monitor noise, including snores from you or someone next to you. It also looks for snore-specific noises, so you will be able to see in the morning whether your own snores, or those of your partner, disturbed you during the night.

The Snore Report highlights two factors: noise level and snoring. The noise level section details how loudly you snored that night. This data will be presented in a chart with dBA, or relative decibels, on the Y-axis, and time on the X-axis. Notably, snoring noise levels range from 30 dBA (very quiet) to 90 dBA or higher (very loud). The snoring section represents how much time you spent snoring during your sleep. It’s presented as a simple bar and percentage. 0-10% is mild, while figures above 40% are termed frequent. Both Snoring events and Total noise are displayed to help viewers differentiate loud background noise from snoring.

Fitbit recommends charging your device to at least 40% before going to bed when using the Snore and Noise Detect feature, as it will cause you to need to charge your Fitbit more often. To enable snore and noise detection, open the Fitbit app and visit the Sleep page. On the sleep page, you’ll see a "Check for snoring" option. If you click on "Learn more," you will be taken to a page that tells you about the snore and noise detect feature. If you click next, then agree and continue to the privacy policies, you will then be able to enable the watch to record your noise levels at night. You can turn the noise detection off at any time in your sleep settings.

Sleep tracking with Fitbit app

Sleep tracking with the Fitbit app

The Fitbit app can be used in conjunction with a Fitbit device to track your sleep. The app provides a detailed breakdown of your sleep, including the duration and quality. It can also provide insights and recommendations to help you improve your sleep routine.

To track your sleep using the Fitbit app, you need to wear your Fitbit device to bed. The device will automatically detect your sleep when your body is completely at rest and you haven't moved for about an hour. It is recommended to wear the device on your wrist in a snug wristband, as it cannot track sleep if worn on a pendant or clip.

The Fitbit app will show your sleep data, including the time spent awake, restless, and asleep. It will also provide a sleep score, which reflects the quality of your sleep based on your heart rate, time spent in different sleep stages, and other factors. The app allows you to view your sleep stats for the current day and previous days, weeks, or months. You can also edit or delete sleep logs within the app.

For more detailed insights and historic data, you can subscribe to Fitbit Premium. This paid subscription service offers personalized recommendations, access to a library of workout videos and audio tracks, and the ability to compare your sleep patterns with baseline values for people of your age and gender.

Frequently asked questions