The Fitbit Versa 4 uses a combination of sensors and algorithms to track sleep stages, including photoplethysmography (PPG) for heart rate monitoring and motion tracking via accelerometers. These sensors help estimate sleep stages by analyzing movement and heart rate patterns. However, the accuracy of Fitbit's sleep tracking is generally reported to be around 69% in any given 30-second window, according to a 2017 study[1]. This means that while Fitbit can provide a general overview of sleep patterns over time, its accuracy might not be as precise as professional sleep monitoring tools like EEG.
Fitbit's algorithm relies on factors such as motion, heart rate, and machine learning to estimate sleep stages. It can sometimes misinterpret periods of restless sleep as wakefulness or vice versa[7]. Additionally, environmental factors like room temperature or noise are not considered in Fitbit's sleep tracking[7]. Despite these limitations, many users find Fitbit's sleep tracking to be generally reliable for monitoring overall sleep patterns and trends, especially when used consistently over multiple nights[1][4].
The Versa 4 offers features like a personalized Sleep Profile, daily sleep stages analysis, and a smart wake alarm, which can help users understand their sleep quality and wake up during a light sleep phase[2]. However, some users have reported issues with the accuracy of sleep data tracking on the Versa 4[3]. Overall, while Fitbit's sleep tracking is useful for general insights, it should be interpreted with some caution and not relied upon for precise medical diagnostics.
Citations:[1] https://www.internationalsleepcharity.org/blog/what-i-learned-from-tracking-my-sleep-with-fitbit-for-two-months
[2] https://www.heartratemonitorsusa.com/products/fitbit-versa-4-smartwatch
[3] https://community.fitbit.com/t5/Versa-4/Versa-4-isn-t-tracking-my-sleep-data-accurately/td-p/5412963
[4] https://connectthewatts.com/2022/10/03/fitbit-versa-4-review/
[5] https://community.fitbit.com/t5/Versa-4/Sleep-tracker-help-Fitbit-versa-4/td-p/5654078
[6] https://www.reddit.com/r/fitbit/comments/1bxv1f0/how_accurate_is_fitbits_sleep_tracker_and/
[7] https://www.builtstrength.com.au/wellness/how-accurate-is-fitbit-for-sleep/
[8] https://support.google.com/fitbit/answer/14236407?hl=en
[9] https://www.reddit.com/r/fitbit/comments/hvxha0/what_you_probably_didnt_know_about_your_fitbit/