Gina Johnson
Sleep is an essential component of health, and its timing, duration, and quality are critical determinants of a person's overall health. The best way to know if you are getting enough sleep is to track it. Fitbit devices can help you do this. They can track your sleep and provide a sleep score based on your heart rate, the time spent awake or restless, and sleep stages. Fitbit devices can detect when you are asleep by tracking your movement and heart rate patterns. If you haven't moved for about an hour, your Fitbit will assume that you are asleep. They can also track 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.
| Characteristics | Values |
|---|---|
| How does Fitbit track sleep? | Fitbit uses movement and heart-rate patterns to estimate sleep stages. It assumes you're asleep when you haven't moved for about an hour. |
| How accurate is Fitbit's sleep tracking? | Fitbit's sensors can classify sleep stages with 69% accuracy in any given 30-second time window. |
| How does Fitbit's accuracy compare to sleep studies? | Sleep stages are traditionally measured in a lab using an electroencephalogram to detect brain activity, along with other systems to monitor eye and muscle activity. |
| How does Fitbit's accuracy compare to other wearables? | Fitbit does not over or underestimate the duration of sleep stages. There is a slight overestimation of REM from sensor readings, but the Fitbit algorithm corrects for this. |
| How does Fitbit calculate the sleep score? | The Fitbit Sleep Score is based on heart rate, the time spent awake or restless, and sleep stages. The score is a sum of individual scores for sleep duration, sleep quality, and restoration, for a total score of up to 100. |
| How can I improve Fitbit's sleep tracking accuracy? | Wear your Fitbit higher on your wrist (2-3 finger widths above the wrist bone) and moderately snugly for the most accurate readings. |
| How often should I charge my Fitbit? | Fitbit has a robust battery life, up to 7 days, so you don't have to choose between nightly tracking and daily wear. |
| Can I track my sleep without a heart rate monitor? | Yes, but it's better to use a heart rate monitor for more accurate results. Older Fitbits without heart rate monitors can only detect sleep from a lack of motion. |
| Can I manually start sleep tracking? | Yes, you can use the "Begin Sleep Now" option in the Fitbit app, but this will not generate sleep stages. |
| Can Fitbit track naps? | Fitbit can detect and record naps that are at least an hour long. |
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What You'll Learn
Fitbit's sleep tracking features
Sleep Detection
Fitbit devices with heart rate tracking capabilities can automatically detect when you're asleep. When your body is completely at rest and you haven't moved for about an hour, your Fitbit device assumes you're asleep. It also considers additional data, such as the length of time you exhibit movements indicative of sleep, like rolling over. This combination of movement and heart rate patterns allows the device to estimate your sleep stages.
Sleep Stages
Fitbit categorizes sleep into three main stages: REM sleep, deep sleep, and light sleep. REM sleep is associated with vivid dreaming and typically occupies a larger portion of the second half of the night. Deep sleep usually occurs in the first few hours of sleep and is characterized by slower breathing, relaxed muscles, and a more regular heart rate. Light sleep serves as the entry and exit point of sleep, where your body transitions between being awake and asleep.
Heart Rate Variability (HRV)
Fitbit devices track beat-to-beat changes in your heart rate, known as heart rate variability (HRV). These fluctuations provide insights into your transition between different sleep stages. By analyzing your heart rate patterns, Fitbit can estimate your sleep cycles and stages for the previous night.
Sleep Score
Fitbit assigns you a Sleep Score based on multiple factors, including heart rate, time spent awake or restless, and sleep stages. The score ranges from 0 to 100, with most users falling between 72 and 83. The score is calculated using three components: sleep duration, sleep quality, and restoration. The restoration component considers estimated oxygen variation, where high variations may indicate disturbances in breathing during sleep.
Smart Wake and Bedtime Reminders
Fitbit offers Smart Wake, which monitors your sleep stages and sets off the alarm during a light sleep stage. This feature aims to help you wake up feeling more refreshed. Additionally, you can set bedtime reminders to maintain a consistent sleep schedule.
Sleep Sensitivity
Fitbit allows you to adjust the sleep sensitivity setting to either "Normal" or "Sensitive." In normal mode, significant movements are recorded as time spent awake. Sensitive mode captures nearly all movements as time spent restless or awake, which may be useful if you often wake up feeling tired despite sufficient sleep duration.
Sleep Profile
Fitbit Premium offers a monthly sleep profile for users with eligible devices. This profile provides a breakdown of your sleep with ten monthly metrics and assigns you a "Sleep Animal" based on your long-term sleep trends. The six Sleep Animals are bear, dolphin, giraffe, hedgehog, parrot, and tortoise, each representing different sleep characteristics.
Snore and Noise Detection
With a Fitbit Premium subscription and compatible devices, you can enable snore and noise detection. This feature uses the device's microphone to track noise levels and snoring during the night. The resulting summary report can provide insights into your sleep environment and potential sleep disturbances.
Sleep Tracking Considerations
For optimal sleep tracking, Fitbit recommends wearing your device snugly on your wrist, positioned higher up toward your elbow. Additionally, ensure your device has sufficient battery life, especially when using features like snore and noise detection, as they can impact battery life.
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How Fitbit estimates sleep stages
You don't need to tell your Fitbit when you sleep. It will automatically track your sleep when you wear your device to bed. However, you can manually edit your sleep log if the start or end times are incorrect.
Fitbit estimates sleep stages by using a combination of movement and heart-rate patterns. When you haven't moved for about an hour, your 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 sleep, 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'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. During the early part of light sleep, you may drift between being awake and asleep, remaining somewhat alert and easily awoken. Your breathing and heart rate usually decrease slightly during this stage. Light sleep promotes mental and physical recovery.
- Deep sleep: This 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, so you become harder to awaken. Your breathing slows down, your muscles relax, and your heart rate usually becomes more regular. Deep sleep promotes physical recovery and supports aspects of memory and learning, as well as your immune system.
- REM sleep: This 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 eyes move quickly in different directions, 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 as your brain processes and consolidates information from the previous day.
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How to set up your Fitbit for sleep tracking
You don't need to tell your Fitbit when you sleep. It will automatically detect when you are asleep when you wear your device to bed. However, there are a variety of settings that can help you tailor the device to your needs. Here is how to set up your Fitbit for sleep tracking:
Set a sleep goal:
- Open the Fitbit app on your phone.
- Tap on the round icon that may (or may not) have your photo, at the top left of the screen.
- Tap Activity and Wellness > Sleep > Time Asleep Goal, and use the pull-down menu to adjust your total sleep target.
- You can also get to this menu by hitting the gear-like Settings icon at the top left of your app's Sleep menu.
Set bedtime and wake-up time:
- In the Fitbit app on your phone, tap on the round icon that may have your photo, at the top left of the screen.
- Tap Activity and Wellness > Sleep > Bedtime and use the pull-down menu to adjust your target bedtime.
- You can then do the same thing for your wake-up time.
Set a bedtime reminder:
- In the Fitbit app on your phone, tap on the round icon that may have your photo, at the top left of the screen.
- Tap Activity and Wellness > Sleep > Bedtime Reminder.
- When you toggle the slider for Reminder, a Time option will pop up. Tap Time to set a time for your reminder as well as picking days of the week when it will be active. (This allows you to skip the reminder on weekends, for example.)
Set a silent alarm:
- To set a silent alarm, go to the main screen of your Fitbit and swipe left until you get the alarm clock icon.
- Tap the time to set the hours and the minutes and then toggle the slider to turn on the alarm.
- The alarm will vibrate but not actually ring when it's time to wake up.
Set a smart alarm:
- If you find yourself tired even after getting a full night's sleep, there's a chance that your alarm is rousing you from a dream (REM sleep) or a Deep Sleep period.
- The Smart Wake feature monitors your sleep stages and wakes you during a Light Sleep stage, in a window of up to 30 minutes leading to the time you've set for the alarm.
- For instance, when I set a 7:07 am alarm on my Fitbit Charge 5, my potential wake-up times ranged from 6:37 a.m. to 7:07 a.m.
- Swipe left to get to the Alarm screen on your tracker.
- Set an alarm if you haven't already, and scroll down to Smart Wake.
- Toggle the slider and check the time range.
Adjust noise sensitivity:
- If you have a Sense or Versa 3 and a Fitbit Premium account, your device can monitor the noise in your bedroom, including your snoring or someone else's.
- If it's snoring, you or your partner could use the information to start a conversation with a doctor.
- If it's outside noise, you could close windows and doors before bedtime or get a white noise generator to drown out the hubbub.
- According to Fitbit, this function affects battery life, so make sure your device is charged to at least 40% before bed.
- To adjust the setting, tap the setting icon on the top right of your app's Sleep page, then tap Sleep Sensitivity and check either Sensitive or Normal.
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How to check your sleep metrics
To check your sleep metrics, you must first sync your Fitbit tracker or watch with your smartphone. To do this, swipe up from the clock face on your tracker or watch to get to the Fitbit Today tab, where you can see your total sleep from the previous night as well as your Sleep Score. On some models, you can also swipe left on the Sleep Tile to see last night's detailed data as well as your sleep history for the week.
For more detailed information about your recent sleep, open the Fitbit app and go to the Today screen. Here, you can scroll down to the snoozing moon icon, which represents Sleep. This screen will show you your total sleep duration, the time you went to bed, and the time you woke up. It will also show you how much time you were awake.
To put the previous night's stats into perspective, tap the plus sign to see details of recent days and weeks, including both nightly sleep duration and a week-to-week average.
To check your sleep stages, tap the sleep duration tile. Swipe down to the Sleep timeline graph. Press and hold the graph, then move your finger left or right to check your sleep stages. Tap the Benchmark or 30-day average tabs to check additional data.
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How to improve your sleep with Fitbit
You don't need to tell your Fitbit when you sleep. Your Fitbit device automatically detects your sleep when you wear your device to bed. It is recommended that you wear your device in a snug wristband while sleeping and that you don't wear your device in a clip or pendant accessory. When your body is completely at rest and you haven't moved for about an hour, your device records that you're asleep.
Set a sleep goal
Open the Fitbit app on your phone. Tap on the round icon that may (or may not) have your photo, at the top left of the screen. Tap Activity and Wellness > Sleep > Time Asleep Goal, and use the pull-down menu to adjust your total sleep target.
Set bedtime and wake-up time
In the Fitbit app on your phone, tap on the round icon that may have your photo, at the top left of the screen. Tap Activity and Wellness > Sleep > Bedtime and use the pull-down menu to adjust your target bedtime. You can then do the same for your wake-up time.
Set a bedtime reminder
In the Fitbit app on your phone, tap on the round icon that may have your photo, at the top left of the screen. Tap Activity and Wellness > Sleep > Bedtime Reminder. When you toggle the slider for Reminder, a Time option will pop up. Tap Time to set a time for your reminder as well as picking days of the week when it will be active.
Set a silent alarm
To set a silent alarm, go to the main screen of your Fitbit and swipe left until you get the alarm clock icon. Tap the time to set the hours and the minutes and then toggle the slider to turn on the alarm. The alarm will vibrate but not ring when it's time to wake up.
Set a smart alarm
If you find yourself tired even after getting a full night's sleep, there's a chance that your alarm is rousing you from a dream (aka REM sleep) or a Deep Sleep period. The Smart Wake feature monitors your sleep stages and wakes you during a Light Sleep stage, in a window of up to 30 minutes leading to the time you've set for the alarm.
Adjust noise sensitivity
If you have a Sense or Versa 3 and a Fitbit Premium account, your device can monitor the noise in your bedroom, including your snoring or someone else's. If it's snoring, you or your partner could use the information to start a conversation with a doctor. If it's outside noise, you could close windows and doors before bedtime or get a white noise generator to drown out the hubbub. According to Fitbit, this function affects battery life, so make sure your device is charged to at least 40% before bed. To adjust the setting, tap the setting icon on the top right of your app's Sleep page, then tap Sleep Sensitivity and check either Sensitive or Normal.
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Frequently asked questions
No, you don't need to tell your Fitbit when you sleep. Wrist-based Fitbit devices and Google Pixel Watch series automatically detect your sleep when you wear your device to bed.
Your Fitbit device knows you're asleep when your body is completely at rest and you haven't moved for about an hour.
Fitbit's sleep feature estimates sleep stages using a combination of movement and heart-rate patterns. Additional data, such as the length of time of movements that are indicative of sleep behavior (such as rolling over), can also help confirm that you’re asleep.
