All Fitbit devices that have heart-tracking capabilities – other than Fitbit Charge HR and Fitbit Surge – have the ability to monitor your sleep stages. The sleep tracker gives you a record of your sleep stages that you can cycle through to see how much time you’re spending in each one.
Sleep stages: what are they?
Your body goes through several sleep stages each night while you sleep. Each one lasts about 90 minutes before you cycle through to the next one. During each stage of the sleep cycle you alternate between deep sleep and light sleep.
When you aren’t in Rapid Eye Movement (REM) sleep, you’ll alternate between the two Non-Rapid Eye Movement (NREM) stages. You spend more time in deep sleep during the beginning of the night.
When you enter into REM sleep, you experience vivid dreams (even if you can’t remember them). The amount of time you spend in REM sleep typically increases as the night goes on. Earlier in the night your REM stages are brief, but when you get closer to waking up you’ll spend a lot more time in the vivid dreaming stage of sleep.
How Fitbit detects what stage of sleep you’re in
Ok, so your Fitbit might not meet the gold standard of using an electroencephalogram in a lab setting. Professional sleep studies detect your brain activity, eye movement, and muscle activity in a controlled environment.
What Fitbit does is estimate the amount of time you’re spending in each sleep stage by using a combination of your movement and your heart-rate patterns. Your tracker assumes you’re asleep if you haven’t moved in one hour. The device cross-references that with other data – movements that indicate sleeping such as rolling over – to confirm that you are asleep.
Your Fitbit then tracks your heart-rate variability (HRV) – the beat-to-beat changes in your heart-rate – that fluctuate when you move between the different sleep stages. When you wake up and sync your Fitbit, the device is able to use that data to estimate the amount of time you spent in light sleep, deep sleep, and REM sleep the previous night.
Steps for viewing your sleep stages
- Sync your Fitbit device using the Fitbit app
- Tap the sleep icon
- Press Today or Last Night (depending on what device you’re using)
- In the top right, tap the expand icon. This will show you information about your sleep cycle. Press the expand icon again to close it.
- Scroll down to view more data. You can press 30 Day Avg and Benchmark to see more data.
Does Fitbit track naps?
Unfortunately Fitbit needs at least 3 hours of data to give you accurate information about your sleep cycle. You aren’t able to see your sleep stage stats for naps.
What does “awake minutes” mean?
When you’re viewing your sleep stage data, you’ll most likely see awake minutes information. The average adult wakes up several times throughout the night. Even though you may not remember waking up, if your Fitbit shows awake minutes then you definitely did.
If you wake up briefly and then fall right back asleep your brain will likely not remember it at all and will assume that you were sleeping throughout the night. If you frequently wake up feeling like you aren’t refreshed, that’s probably an indicator that you woke up frequently throughout the night and you’ll see a higher amount of awake minutes in your app.
Why is Fitbit showing me my sleep pattern instead of sleep stages?
According to Fitbit, there are a few scenarios where you’ll see a sleep pattern instead of the more detailed sleep stages data.
- If you wear your Fitbit too loose. Wearing it too loose or in a position where it can’t get accurate heart-rate data will cause you to lose data. The company recommends wearing it 2-3 finger widths height on your wrist. It should feel secure but not tight.
- If you didn’t sleep long enough. You must sleep at least 3 hours to get accurate data.
- If you’re Fitbit’s battery is low.
- If you used the Begin Sleep Now option. You don’t need to use this option. Instead you should just wear the device to bed.
What is Smart Wake?
If you’re using a Fitbit Charge 3, Fitbit Charge 4, Fitbit Ionic, or Fitbit Versa then you can turn on Smart Wake when setting an alarm. This will prevent you from waking up when you’re in the deep sleep stage.
Smart Wake attempts to find the best time to wake you up starting 30 minutes before the time you set your alarm for. It prevents you from waking up in deep sleep which will help you feel more refreshed and less groggy. If Smart Wake can’t find an optimal time to wake you up, it’ll default to the time you set.