Fitbit vs medical community sleep stages

[shippee]

Fitbit has: a) Awake, b) REM, c) Light, and d) Deep for measuring sleep.

The medical community uses 4 stages (there used to be 5): 

N1 (Stage 1) - Light Sleep (5%)
N2 (Stage 2) - Deeper Sleep (45%)
N3 (Stage 3) - Deepest Non-REM Sleep (25%)
REM (25%)

Aside from REM, I don't see much of a correlation - is that correct, Fitbit??

Also, I recently had my 5th sleep study which showed 33 minutes of Stage R (REM), while Fitbit showed 46 minutes of REM. Also sleep study showed 0 minutes of N3 (Deep) sleep while Fitbit showed 39 minutes of Deep.

Has Fitbit ever done testing in the lab for Fitbit with Polysomnography testing for calibration purposes? Seems to be quite the disparity ... your thoughts?

Moderator edit: clarified subject.

[N8teGee]

Hi @shippee

Honestly I would not trust any wrist based device when it comes to accurately measuring sleep stages, there just isn't enough data available. I know this doesn't really answer your question tbough. Personally I mostly pay attention to my sleep and awake times and duration, which seem to be pretty accurate.