What should I know about sleep stages?

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If you use a Fitbit device with heart-rate tracking (except Fitbit Charge HR or Fitbit Surge) to track your sleep, you can see a record of the sleep stages you cycle through at night. This article answers frequently asked questions about sleep stages. For other questions about sleep, see How do I track my sleep? 

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What are sleep stages?

While you’re asleep each night, your body typically goes through several sleep cycles that last on average 90 minutes. In each cycle you alternate between two types of sleep: 

Light Sleep and Deep Sleep—With less brain activity than REM sleep, non-rapid eye movement (NREM) includes the stages of light sleep and deep sleep. Periods of deep sleep are typically longer early in the night.

Rapid Eye Movement (REM) Sleep—The stage associated with vivid dreams, REM sleep periods are typically longer as the night goes on (source).
During a sleep cycle, it’s most common to go from light sleep to deep sleep, back to light sleep, and then into REM sleep. Then the cycle generally repeats, but sleep patterns vary naturally. 

How does my Fitbit device automatically detect my sleep stages?

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. While this method is the gold standard for measuring sleep stages (source), your device can estimate your sleep stages in a more comfortable, convenient way.

Fitbit estimates your sleep stages using a combination of your movement and heart-rate patterns. When you haven’t moved for about an hour, your tracker or watch assumes that you’re asleep. Additional data—such as the length of time your movements are indicative of sleep behavior (such as rolling over, etc.)—help confirm that you’re asleep. While you’re sleeping, 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, we use your movement and heart rate patterns to estimate your sleep cycles from the previous night. 

What does each sleep stage mean?

Fitbit’s sleep researchers and the National Sleep Foundation describe the following sleep stages. The names of the stages are what we’ve chosen to use in your Fitbit sleep log. 

Light Sleep

Light sleep serves as the entry point into sleep each night as your body unwinds and slows down. This stage typically begins within minutes of falling asleep. During the early part of light sleep, you may drift between being awake and asleep. You may be somewhat alert and can be easily awoken. Breathing and heart rate typically decrease slightly during this stage.  

Light sleep promotes mental and physical recovery.

Deep Sleep

Deep sleep typically occurs in the first few hours of sleep. When you wake up feeling refreshed in the morning, you’re likely to have experienced solid periods of deep sleep during the previous night. During deep sleep, it becomes harder to be awakened since your body becomes less responsive to outside stimuli. Breathing becomes slower and muscles relax while heart rate usually becomes more regular. Adults may see a normal decrease in deep sleep as we get older, though sleep patterns vary among people. 

Deep sleep promotes physical recovery and aspects of memory and learning. This stage has also been shown to support your immune system. 

REM Sleep

The first phase of REM sleep typically occurs after you’ve had an initial stage of deep sleep. You generally stay in REM sleep for a longer period of time during sleep cycles occurring in the second half of the night. During this final stage of sleep, your brain becomes more active. Dreams mainly occur during REM sleep, and your eyes move quickly in different directions. Heart rate increases and breathing becomes more irregular. In principle, muscles below the neck are inactive to avoid acting out dreams.

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 so that it can be stored in your long-term memory.

How do I see my sleep stages?

Follow the steps below to see your sleep stages data in the Fitbit app: 
  1. In the morning, open the Fitbit app and sync your Fitbit device.
  2. Tap the sleep tile. (If it says "Analyzing your sleep", your device's data hasn't synced yet.)
  3. Tap Today (on Windows 10, tap Last Night). 
  4. Tap the expand icon in the top right to open information about your sleep stages, and swipe to view your stats. Tap the icon again to close. 
  5. Scroll down to view your time spent in each stage, and tap 30 Day Avg and Benchmark to view additional stats.

How do I use the sleep stages benchmark?

The benchmark is based on published data and shows how your sleep stage estimates from the previous night compare to the averages of others who are the same age range and sex (source). In the graph, the typical range for each sleep stage is shown as the shaded area between the two horizontal lines. Keep in mind sleep cycles vary naturally, and you’ll likely see your sleep data fall outside the typical ranges at times. Another way to analyze your sleep stages is to compare your data from last night to your own 30 day average (under the 30 Day Avg tab), as your sleep patterns may vary over time.
User-added image

How can I see the start and end times for my sleep stages?

See the start and end times for your different sleep stages to gain insight into your sleep patterns.

For instructions, choose a section below:

  • Fitbit app
    1. Tap the Today tab User-added image, then tap the Sleep tile.
    2. Tap the sleep record you want to see more details about.
    3. Tap the sleep graph to expand it (iOS and Android only).
    4. Tap and hold the sleep graph to see the estimated sleep stages recorded at different times. On iOS, slide your finger to see the time ranges. 
  • dashboard
    1. From the dashboard, click the Sleep tile > See More.
    2. Click the sleep record you want to see more details about.
    3. Hover your mouse over the sleep graph to see the estimated sleep stages recorded at different times.

Can this tell me if I have apnea or any other sleep disorder?

Your sleep stages data helps you track your patterns and notice variations. If you have any concerns about your sleep health we recommend sharing the information with your doctor. A good source of additional information is the National Sleep Foundation

Why do I see awake minutes?

It’s normal to see awake minutes in your sleep stages; studies have shown a typical adult could wake up briefly between 10-30 times per night (source). You may not remember waking up since you likely fell right back to sleep, especially if you were awake for less than 2-3 minutes at a time. If you wake up in the morning feeling like you had a restless night, you may notice more awake minutes in your sleep stages as compared to other nights.

If you previously tracked sleep with Fitbit, your log included the time spent awake, restless, and asleep. We’ve fine-tuned the mechanism we use to track sleep in order to estimate your sleep stages by including heart rate and other data. As a result, we’ve combined the time you spend awake and restless into total awake minutes to give you a better sense of your sleep cycles. 

You may notice more awake minutes in sleep stages than in your previous sleep data due to this change. If you're concerned about meeting your Fitbit goals, you can edit your sleep goal to make sure you still hit it. For instructions, see How do I track my sleep?

Note that sleep stages aren't affected by the sleep sensitivity setting on your device. For more information, see How do I track my sleep?

Why don't I see sleep stages today?

There are a few scenarios where you might see your sleep pattern (which shows your time asleep, restless, and awake) instead of sleep stages:
  • If you slept in a position that prevented your device from getting a consistent heart-rate reading or wore it too loosely. For best results, wear your device higher on your wrist (about 2-3 finger widths above your wrist bone). The band should feel secure but not too tight.
  • If you used the Begin Sleep Now option in the Fitbit app (instead of simply wearing your device to bed). For more information on automatic sleep tracking, see How do I track my sleep?
  • If you slept for less than 3 hours.
  • If your device’s battery is critically low.
For more information about why you see your sleep pattern, tap or click the sleep record that shows your sleep pattern.
Image of fitbit app explaining why sleep stages are not available.

Why don’t I see sleep stages for naps?

Your device needs at least 3 hours of sleep data to estimate your sleep stages, so you won’t see sleep stages for shorter naps.

    Can I edit my sleep stages data?

    If your sleep start or end times are incorrect, you can manually edit your sleep log to better reflect your time asleep. Note that if you extend your time asleep, you may see gaps at the start or end times of your sleep stages. For step-by-step instructions, see How do I change my sleep history?

    What are some tips for getting a good night’s sleep?

    There are several steps you can take to increase your chances for getting a good night’s sleep. The National Sleep Foundation suggests sticking to a sleep schedule, avoiding naps in the afternoon, practicing a relaxing bedtime routine, and exercising daily among other recommendations.

    Additionally, Fitbit offers several tools to help you sleep better. You can set a sleep schedule in the Fitbit app to help you maintain a more consistent pattern of sleep. For step-by-step instructions, see What should I know about setting a sleep schedule? You can also learn about your sleep habits through sleep insights and set a bedtime reminder in the Fitbit app to help you wind down for sleep each night. For more information, see How do I track my sleep?

    For more information on sleep stages, see our blog posts REM, Light, Deep: How Much of Each Stage of Sleep Are You Getting? and Your Heart Rate Is the Key to Smarter Sleep Stages. Here’s Why. 

    For additional sleep information including tips for feeling rested, visit the Fitbit blog.

    Can my Fitbit device adjust my alarm based on my current sleep stage?

    When you set an alarm on Fitbit Charge 4, Fitbit Ionic, or Fitbit Versa series, turn on Smart Wake to avoid being awoken while in deep sleep. Smart Wake attempts to find the best time to wake you starting 30 minutes before the alarm time you set. It avoids waking you during deep sleep so you're more likely to wake up feeling refreshed. If Smart Wake can’t find the best time to wake you, your alarm alerts you at the set time. For more information, see How do I manage alarms on my Fitbit device?
    Last updated: July 7, 2020
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