Fitbit Sleep Tracker: How Accurate Is It Really?

Sleep trackers have become an increasingly popular way to monitor sleep quality and duration. Fitbit is one of the most popular sleep trackers on the market, but how accurate is it? Fitbit uses motion tracking, heart rate monitoring, and machine learning to estimate sleep duration and quality. While it provides valuable feedback that can help users adjust their sleep schedules, it has limitations and may not always accurately distinguish between different sleep stages.

Fitbit sleep tracking accuracy compared to other devices

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?

According to a paper published by Fitbit scientists in 2017, the watch's sensors can classify sleep stages with 69% accuracy in any given 30-second time window. This means that Fitbit's sleep staging is only correct slightly more than two-thirds of the time, and this fact is not communicated to users in the Fitbit app. Therefore, if you only use Fitbit for one night, take the app's sleep staging with a few grains of salt.

Comparing Fitbit with a professional scientific encephalography (EEG), Fitbit is 72-73% accurate, while the Oura Ring v.2 is slightly more accurate. Fitbit is almost 100% accurate for REM sleep (only a 0.2% difference) and very close for deep sleep (only a 3.6% difference). However, it confuses some light sleep as being the awake phase.

On average, Fitbit sleep trackers tend to overestimate total sleep time by about 10% and underestimate measures of deep sleep and REM sleep by about 20% each. As deep sleep and REM sleep are considered the most important for recovery and memory consolidation, this means your Fitbit may tell you your sleep is worse than it actually is.

How does Fitbit compare to other sleep trackers? Apple Watches, Garmin watches, Oura rings, and Whoop bands have also been studied in a similar manner. 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). 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 and light sleep time and underestimate deep and REM sleep. Lastly, the Oura Ring and Whoop Band are the most accurate at estimating total sleep time.

Therefore, while Fitbit sleep trackers are not perfect, they are comparable to other devices on the market. They can provide valuable feedback on your sleep that could help you adjust your sleep schedule to get more rest.

Fitbit's accuracy in measuring sleep stages

Fitbit's sleep-tracking algorithm relies on motion tracking, heart rate monitoring, and machine learning to estimate sleep duration and quality. Motion tracking uses accelerometers to detect movement during sleep, with less movement generally indicating deeper sleep. Heart rate monitoring helps estimate periods of wakefulness, with higher heart rates associated with increased alertness.

Research has shown that Fitbit sleep trackers tend to overestimate total sleep time by about 10% and underestimate deep sleep and REM sleep by about 20% each. This means that your Fitbit may tell you that your sleep is worse than it actually is, and improvements in your sleep quality may go unregistered. When compared with professional scientific encephalography (EEG), Fitbit's accuracy is around 72-73%. Fitbit is also said to be very accurate in measuring REM sleep, with only a 0.2% difference, and close for deep sleep, with a 3.6% difference. However, it may confuse some light sleep with the awake phase.

Fitbit's algorithm has been criticized for lacking the depth of information provided by more advanced methods such as polysomnography (PSG), which is considered the standard for tracking sleep activity. PSG detects sleep stages through biosignals, while Fitbit relies solely on movement and heart rate data, which may not always accurately reflect sleep stages. For instance, if you are reading quietly in bed, your Fitbit may think you are asleep. Additionally, Fitbit does not consider external factors such as room temperature, noise, or disturbances that can affect sleep quality.

Despite these limitations, Fitbit sleep trackers are still a popular and useful tool for monitoring sleep. They provide valuable feedback on sleep patterns, helping users adjust their sleep schedules to get more rest. However, it is important to remember that they may not always provide a perfectly accurate representation of your sleep stages, and becoming overly focused on the data may be detrimental to your sleep quality.

How does Fitbit's sleep tracking work?

Fitbit's sleep-tracking algorithm relies on motion tracking, heart rate monitoring, and machine learning to estimate sleep duration and quality. The motion-tracking feature uses accelerometers to detect movement during sleep, as people tend to move less when in a deep sleep. Heart rate monitoring is used to estimate periods of wakefulness, as a higher heart rate may indicate that the wearer is awake. Fitbit uses a machine learning algorithm to analyse this data.

However, the accuracy of Fitbit's sleep-tracking algorithm has been called into question. Fitbit's algorithm lacks the depth of information provided by polysomnography (PSG), an accurate standard method for measuring sleep that uses biosignals to detect sleep stages. Fitbit sleep trackers do not consider external factors such as room temperature, noise, or disturbances, which can affect sleep quality. Research has shown that Fitbit sleep trackers tend to overestimate total sleep time by about 10% and underestimate deep sleep and REM sleep by about 20% each.

Despite the limitations of Fitbit's sleep-tracking algorithm, it can still provide valuable feedback on sleep habits and help users make adjustments to their sleep schedules to get more rest. It is important to remember that the quest for a perfect report or the "right" amount of sleep can be detrimental to one's health, and becoming overly focused on sleep data can contribute to insomnia.

Pros and cons of using Fitbit to track sleep

Pros of using Fitbit to track sleep

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. Fitbit’s sleep tracking algorithm relies on motion tracking, heart rate monitoring, and machine learning to estimate your sleep duration and quality.

The Fitbit Versa infers when you’re sleeping and what stage of sleep you’re in using an accelerometer (an instrument for measuring bodily accelerations of the wrist) coupled with a technique called optical photoplethysmography, or PPG. PPG measures blood flow based on how green light from an LED on the back of the watch is reflected by the body.

Fitbit Premium offers several tools that may help you get better sleep, including a daily sleep score breakdown that can help you understand where you can improve your sleeping habits and receive personalized guidance. Fitbit Premium also has guided programs developed with sleep experts, including Habits for Restful Sleep, aimed at helping you build better daytime habits to help achieve deeper sleep at night.

Cons of using Fitbit to track sleep

Fitbit sleep trackers are not super accurate. On average, they 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.

Fitbit’s algorithm lacks the depth of information provided by methods such as electroencephalography (EEG) and polysomnography, which are used by sleep experts to precisely categorize sleep stages. Fitbit sleep trackers also don’t consider external factors such as room temperature, noise, or disturbances from partners or pets that can affect sleep quality.

How to improve sleep with a Fitbit

Fitbit sleep trackers have gained immense popularity as a way to monitor sleep. They provide information about the quality and duration of your sleep, helping you make informed decisions about your sleep habits. While they are not as accurate as professional scientific electroencephalograms (EEGs), Fitbits are still quite accurate in tracking sleep, with some sources claiming they are 72-73% accurate. They are especially good at tracking REM sleep, with only a 0.2% difference, and very close for deep sleep, with only a 3.6% difference.

• Maintain a consistent sleep schedule: The CDC recommends 150 active minutes per week, so try to stick to a sleep schedule that works for you.
• Set a bedtime reminder: Use the Fitbit app to set a bedtime reminder to let you know when it's time to start winding down.
• Avoid distractions: Stop checking your phone, drinking a lot of water, and eating heavy snacks before bed. If you're a light sleeper, turn on the "do not disturb" mode on your phone to avoid midnight wake-ups.
• Engage in relaxing activities: Before bed, try relaxing activities such as taking a bath, reading, or doing yoga.
• Check your sleep duration and quality: Use the Fitbit app to check your average sleep duration and quality, and pay attention to how you feel each day. If you feel sluggish, you may need to adjust your sleep schedule.
• Reduce caffeine and alcohol intake: Caffeine and alcohol can impact your sleeping heart rate, so try reducing your intake if you're having trouble sleeping.
• Work on your overall sleep habits: Improve your sleep habits, heart health, and activity levels to increase your sleep score in the Fitbit app.
• Use Smart Wake: When setting an alarm on your Fitbit, use the Smart Wake feature to allow your device to find the best time to wake you, starting 30 minutes before the set time.
• Use Sleep Profile: If you have a Charge 5, Charge 6, Inspire 2, Inspire 3, or Luxe tracker, or any Sense or Versa watch (except the 2018 model), you can access the Sleep Profile feature, which provides a detailed monthly breakdown of your sleep.

Frequently asked questions