Fitbit tracks sleep using a combination of your heart rate, stillness that lasts about an hour, and small movements such as rolling in bed. The heart rate and movement data enables Fitbit to give you a more precise analysis of your sleep cycle.
Every Fitbit device monitors and logs sleep in stages to show you how long you’ve been asleep in each stage and how well you sleep. You even get a sleep score to understand your sleep patterns and quality, so you can develop better bedtime habits and get the best sleep possible every night.
One important rule is you have to wear the Fitbit for a whole night for it to track your sleep.
How Does Fitbit Know I’m Asleep?
A Fitbit knows you’re sleeping by measuring your brain activity, heart rate, and muscle movements.
With the help of advanced signal processing and machine learning, Fitbit is able to measure heart rate variability in your sleep, making it easy to determine whether your body is in motion between different sleep stages.
Fitbit then determines how much time you spent sleeping by subtracting awake and restless time from your overall sleep time.
How Accurate is Fitbit Sleep?
Fitbit sleep is not 100% accurate. Heart rate variability and body movements vary from time to time based on physical and psychological factors, thus varying sleep data.
According to a study by the “National Library of Medicine”, Fitbit sleep stats are merely estimates rather than accurate results with absolute certainty.
Motion misinterpretation, such as when Fitbit considers periods of restless sleep as wakefulness, and wild variation in heart rate variability, especially in days of intense workouts, make it difficult for Fitbit to give accurate stats.
Additionally, Fitbit devices aren’t as advanced as electroencephalograms used by sleep experts. And because the wearable algorithm lacks the depth of information present in electroencephalograms, there will always be subjectivity in sleep stages. Even external factors, such as noise, room temperature, and disturbance from a partner can equally affect the quality of your sleep.
In a more practical sense, expect a sleep accuracy of at least 69% from the more recent Fitbit devices such as Versa 4 and Sense 2. Furthermore, you get more helpful sleep information in the Fitbit app if you continue to use the fitness tracker or smartwatch in more nights for sleep tracking.
What Are The Different Fitbit Sleep Stages?
There are four Fitbit sleep stages: awake, light sleep, deep sleep, and REM sleep. A Fitbit wearable is able to determine how much time you spend in each stage based on accelerometer data, a set of rules, and heart rate variability.
1. Awake
Awake is a sleep stage that indicates how many times you’ve woken up during sleep, and the normal range is between 10 and 30 minute every night.
2. Light Sleep
In light sleep, your body slows down to a state where you start to fall asleep. And despite being asleep, you’re fully aware of everything going on around you, so even a gentle touch from your partner is enough to jump you back to the awake stage.
Your heart rate will decrease in light sleep, you’ll experience mental and physical recovery, and you’ll and feel better about yourself.
3. Deep Sleep
In deep sleep, your body relaxes from the long day you’ve had. You become completely unresponsive, your muscles relax more, and your breathing slows compared to when you’re awake.
Your heart rate switches from decreasing to regular. And in addition to boosting your immune system and helping with physical recovery, deep sleep helps with memory improvement.
4. REM Sleep
REM takes place in the second half of the night and it usually lasts longer than awake, light, and deep sleeps.
In REM (Rapid Eye Movement), your eyes shift from side to side, your brain become active, and your heart rate increases.You might dream in REM sleep, but your muscles remain inactive to keep you from acting out what you see in those dreams.
Fitbit monitors changes in your heart rate to determine whether you’re in REM sleep or in a completely different stage. An increase in heart rate indicates that your body has entered the REM sleep, and your brain tends to be more active during this period.
How Does Fitbit Assign a Sleep Score?
Fitbit assigns a sleep score based on duration, quality, and restoration of your sleep.
Duration refers to the time you spent asleep and the time you spent awake. Quality focuses on how much time you spent in deep and REM sleep. And restoration looks at your sleeping heart rate and restlessness.
Fitbit then finds the sum of your sleep duration, quality, and restoration based on a score of 100.
Why Can I See a Sleep Score on My Fitbit?
If sleep score is not showing on your Fitbit, it’s likely because all-day sync is off, sleep sensitivity mode is normal, or the optical heart rate sensor is disabled. Sometimes it’s because of a sync problem or the Fitbit app is not up to date.
What’s the Best Fitbit for Sleep Tracking?
The best Fitbit for sleep tracking is a fitness tracker or smartwatch that can give you stats you can depend on, as long as the device has a heart rate monitor.
While the results won’t be 100% accurate, the sleep stats you get should be useful enough to help you improve the quality of your sleep over time.
Fitbit models such as Versa 4 and Charge 6 are good options to consider if you’re looking for my recommendations. One of the advantages of these devices is that they include sleep scores, which give you a clear view of your sleep patterns.
How to Use Fitbit for Sleep Tracking
To use your Fitbit smartwatch or fitness tracker for sleep tracking:
- Charge the device before bedtime.
- Set up your sleep schedule.
- Configure bedtime reminders and smart wake.
- Wear the Fitbit to sleep.
- View your sleep data.
Charge the Device Before Bedtime
The first step is to charge your Fitbit smartwatch or fitness tracker 30 to 60 minutes before bedtime, so the device has enough battery level to monitor your heart rate, stillness, and movements throughout the night.
Set Up Your Sleep Schedule
Fitbit automatically creates a customized sleep schedule for you based on the sleep data it collects for five nights. The device looks at the time you wake up and set your bedtime accordingly based on your sleep goals.
However, it’s best to create your own personalized sleep schedule rather than using the preset option.
- Open the Fitbit app.
- Select the Sleep tile.
- Tap the three dots on the top right of the screen.
- Choose Settings.
- Update the Target Sleep Schedule to your liking.
Configure Bedtime Reminders and Smart Wake
Bedtime Reminders help you maintain a consistent sleep schedule. The feature sends a notification to your Fitbit when it’s time retire to bed, as long as you have notifications enabled.
Smart Wake gets you up when you’re in light sleep and feel more rested to get out of bed. What I love about Smart Wake is that it selects an optimal time within a half an hour window before your set alarm goes off.
To configure Bedtime Reminders:
- Open the Fitbit app on your phone.
- Select the sleep tile under Today tab.
- Tap the gear icon on the top-right corner of the screen.
- Enable Bedtime Reminders feature.
- Set your preferred time and frequency.
For Smart Wake:
- Open alarm on Fitbit.
- Set up an alarm that suits you.
- Enable the Smart Wake feature.
Wear Your Fitbit to Sleep
Your Fitbit has to make proper contact with your skin for the optical heart rate sensor to work. Therefore, proper Fitbit placement is crucial. You can have the device on your dominant or non-dominant wrist. Only ensure you tighten the bands to a snug fit.
As you sleep, your Fitbit will use a combination of your heart rate, stillness, and small movements (such as rolling, tossing, and turning) to determine your sleep quality and score.
How to Check Advanced Sleep Insights on Fitbit
To see your sleep data on a Fitbit smartwatch or fitness tracker:
- Swipe up on the screen.
- Choose the Sleep Tile.
- Swipe left to access your sleep pattern.
Your sleep pattern has crucial information at a glance, including time spent awake, restless, and asleep. Additionally, you have access to up to 7 days of your sleep stats on the device.
To see advanced insights of your sleep:
- Open the Fitbit app on your phone.
- Tap “Today”.
- Tap the Sleep tile.
Swiping the graph will show you the duration of your sleep, your sleep routine, and sleep stages. Below the graph, you’ll see your sleep cycles, which show more details about your stages all night.
You can choose the day you want to view and compare your data accordingly. The data comparison is useful in helping you develop a healthier sleeping habit over time.
More advanced features and insights such as sleep profiles, in-depth sleep stage analysis, noise sensitivity, and heart rate and restlessness analysis are available only on the Fitbit premium plan.
What Does a Normal Sleep Pattern Look Like on Fitbit?
A normal sleep pattern on Fitbit is shows you’re getting a good night’s sleep, which is what you should be aiming for. It’s normal to wake up or feel restless at the end of every sleep stage, but that shouldn’t occur regularly if you have good sleeping habits.
What is Restless Sleep on Fitbit?
Restless sleep on Fitbit means you tossed and turned in your deep sleep excessively. In this case, your device will record this data as time spent awake.
It’s normal to have restless sleep, with 10 to 30 rounds of turns and tosses being fine. Still, you should aim to get at least 7 to 8 hours of sleep for adults.
Why Can’t I See My Sleep Stats for Last Night?
You can’t see stats for the previous night because your Fitbit stopped tracking sleep. This could be because of a failed heart rate sensor, a system glitch, obsolete software, wrong device placement, low battery levels, and missing sleep sensitivity settings for devices without optical heart rate sensors.
Restarting the device, charging the battery, and configuring the right settings help fix the problem and get the device tracking sleep properly again.
