What’s the Difference Between Fitbit’s Classic Sleep and Sleep Stages Data?

[yuhang]

Hi all,

I'm currently analyzing sleep data from the Fitbit API and noticed two different sleep level designs recorded on the same day. One format includes asleep, awake, and restless, while the other uses light, deep, REM, and wake. After consulting the Fitbit API documentation, I found the following definitions:

• Classic: Short for "Classic Sleep." This sleep data is recorded with a 60-second granularity. "Sleep Pattern" levels include asleep, restless, and awake.
• Stages: Short for "Sleep Stages." This sleep data is recorded with a 30-second granularity. "Sleep Stages" levels include deep, light, REM (rapid eye movement), and wake.

However, I'm still unclear about the practical differences between these two models. Could anyone help clarify this? Thank you! 

Best
Yuhang

[JohnnyRow · Accepted solution]

For one thing, you need at least 3 hour of sleep to get sleep stages.  If you take a 2 hour nap in afternoon, you will never get sleep stages.

Also you might not get sleep stages under certain other circumstances, such as if it does not get continuous signal, perhaps because tracker is too loose and slips around on wrist during night.
Also, I found out by experience, certain heart arrhythmias can mess up heart beat enough to prevent Fitbit from getting steady enough signal to get sleep stages.

[yuhang]

Great! That's very helpful! Thank you, Johnny!