Over on the Garmin sub-reddit (/r/Garmin), whenever someone asks about the sleep monitoring of their new device, invariably someone will respond with something like “Garmin’s sleep tracking is crap” or “it’s not nearly as good as my Fitbit was”.
All I can say is, it works pretty well for me. The two images shown below are pretty typical of my results. The “Bed Time” and “Wake Time” are practically perfect and the Deep/Light/REM/Awake periods seem to coincide with my recollection of how I slept on those particular nights. Unlike the study mentioned above, I obviously have no reference device to compare results.
Stress
Garmin devices such as my Forerunner 245 Music and vívomove HR also measure daily stress. The graphs shown below include the days before, during, and after an emergency root canal that I recently required. It’s not hard to see where the two dental visits occurred.
Conclusion
The accuracy of sleep and stress monitoring obviously depends on the accuracy and reliability of the device’s built-in optical heart rate sensor. Just as folks are quick to dismiss a particular brand or device’s sleep monitoring, they can just as quickly dismiss built-in optical HR as never being as accurate as a chest strap. The reality is that wrist-based optical heart rate is highly individual and depending on your skin tone, fat content, thickness, hair, how the device is worn, and any number of other factors, some folks will get much better results than others.
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