Fitbit sleep tracker accuracy: in this article we break down just how accurate Fitbit is for sleep.
By Coach Hunter Bennett
Fitbit sleep trackers have gained immense popularity as a way to monitor sleep. They provide information regarding the quality and duration of your sleep, helping you make informed decisions about your sleep habits.
But are Fitbit sleep trackers as accurate as they claim to be?
How does Fitbit track your sleep?
Fitbit’s sleep tracking algorithm relies on the following factors to estimate your sleep duration and quality:
- Motion Tracking: Fitbits use accelerometers to detect movement during sleep. When you’re in a deep sleep, you generally move less, while in REM (rapid eye movement) sleep and lighter sleep stages you tend to move more.
- Heart Rate Monitoring: Fitbits monitor your heart rate throughout the night. They use this to estimate periods of wakefulness.
- Machine Learning: Fitbit uses a machine learning algorithm to analyse your movement and heart rate data. This is said to improve its ability to distinguish between different stages of sleep.
- Additional factors: Fitbit’s algorithm also uses your age, gender, and physical activity levels in its sleep estimation.
The Limitations of Fitbit Sleep Tracking.
While Fitbit’s sleep tracking technology may sound impressive, there are some key limitations that can impact its accuracy and reliability:
- Motion Misinterpretation: Fitbit’s reliance on motion tracking can lead to inaccuracies. For example, it might interpret periods of restless sleep as periods of wakefulness, or in other instances, classify periods where you are awake but not moving as sleep.
- Heart Rate Variability: Your heart rate can vary wildly, even during sleep. For example, your heart rate is likely to be higher if you exercise, eat a large meal, or drink alcohol before bed. As a result, Fitbit’s heart rate sensors may struggle to accurately identify sleep stages.
- Subjectivity of Sleep Stages: Determining sleep stages using motion and heart rate is a simplified approach. Sleep experts often use electroencephalography (EEG) and other advanced methods to precisely categorize sleep stages. Fitbit’s algorithm lacks the depth of information provided by these methods.
- Environmental Factors: Fitbit sleep trackers don’t consider external factors such as room temperature, noise, or disturbances from partners or pets that can affect sleep quality.
How accurate is Fitbit for sleep: What the science says.
Given the popularity of sleep trackers, there has been an influx of research exploring their accuracy – with a lot of this research revolving around Fitbit sleep trackers, as they are the most common.
This research generally involves getting a bunch of people to undergo a sleep study known as a “polysomnography” (which is an extremely accurate way to measure sleep) while wearing a commercial sleep tracker (i.e., a Fitbit).
They then compare the results of the sleep tracker against the polysomnography to determine how accurate they are.
So, what have they found?
Well, in short, that they are not super accurate.
On average, Fitbit sleep trackers tend to overestimate total sleep time by about 10%, and underestimate measures of deep sleep and rapid eye movement (REM) sleep by about 20% each.
As deep sleep and REM sleep are considered to be the most important for recovery and memory consolidation, this means your Fitbit is going to tell you your sleep is actually worse than it really is.
It may also mean that if you try and improve your sleep quality, it may not register any positive effects that are occurring, even if your sleep really is improving.
How does Fitbits sleep accuracy compare to other sleep trackers?
So you might be wondering whether other sleep trackers, such as Apple watches, Garmin watches, Oura rings, or Whoop bands, are more accurate than your Fitbit – and the good news is they have also been studied in a similar manner.
However, there is also some bad news.
They are not really any more accurate than your Fitbit, where almost all of them do a passable job of estimating total sleep time (~80-90% accurate), but they all do a poor job of identifying specific sleep stages (50-65% accurate).
On average, the apple watch is the least accurate sleep tracker, severely overestimating total sleep time, REM sleep, and deep sleep.
The next “worst” are Garmin sleep trackers, which overestimate total sleep time by a moderate amount, overestimate light sleep time by a large amount, and underestimate deep and REM sleep.
Lastly the Oura ring and Whoop band are the most accurate at estimating total sleep time. Although the Oura ring tends to overestimate light sleep and underestimate REM sleep, while the Whoop underestimates both light and deep sleep, and overestimates REM sleep.
The negatives of sleep tracking.
Now you might be thinking that while Fitbits and other sleep devices may not be that accurate, they can still provide positive information that you can use to improve your sleep.
But this may not be the case – and it comes down to “sleep anxiety.”
Sleep anxiety describes a feeling of stress or fear about going to sleep. And as you might expect, it makes it harder to fall asleep.
Now what does this have to do with sleep trackers?
There is evidence to suggest that the data provided by sleep trackers can increase the signs and symptoms of sleep anxiety, in turn, making sleep worse.
In short, sleep trackers can make you think too much about falling asleep, which (as I am sure most of you have experienced at one time or another) makes it harder to sleep!
How to improve your sleep without tracking.
One thing to note is that you don’t need sleep data to improve your sleep. In fact, by simply focusing on some simple tips, you can cause large improvements in sleep quality without the stress of sleep tracking.
- Stick to a Consistent Sleep Schedule: Go to bed and wake up at the same time every day to regulate your internal clock.
- Create a Relaxing Bedtime Routine: Prioritise calming pre-sleep activities like reading for 20-30 minutes before going to sleep.
- Optimize Your Sleep Environment: Keep your bedroom cool (approximately 15-20 degrees Celsius), as dark as possible dark, and as quiet as possible.
- Limit Screen Time Before Bed: Avoid screens (phones, tablets, computers) approximately 60 minutes before bed.
- Stay Active: Engage in regular exercise.
- Watch Your Diet: Avoid large meals and alcohol immediately before bed, and make sure to have your last caffeine-containing beverage before 1-2pm.
Conclusion: Fitbit Sleep Tracker Accuracy?
In summary, while Fitbit and most other sleep trackers do a passable job of estimating how long you were asleep for, they struggle to predict how long you were in specific sleep stages.
As a result, they may not provide you with the information you need to improve your sleep and may even increase sleep anxiety.
Instead, your best bet is to focus on the things known to improve sleep quality without tracking your sleep and simply enjoy the sleep gains!
Want to know how sleep impacts your gains? Read our recent article is 6 hours of sleep enough to build muscle?