Anecdote here, but the only place from which you'd get "data" is from FitBit, and that's what you're trying to calibrate. My wife's got a bunch of sleep issues

Anecdote here, but the only place from which you'd get "data" is from FitBit, and that's what you're trying to calibrate. My wife's got a bunch of sleep issues, and she finds her fitbit data correlates really tightly with her sleep experience. When she's had a sucky sleep night, the fitbit reports lots of awake time, and when she wakes feeling great, that's also reflected. Since her experience is volatile, it seems it'd be hard for fitbit to correlate over years if it was making stuff up. More, the miscues she can observe while awake are all giggle-worthy "Well that makes sense" items. There have been some times she's been entranced in some video or something, sitting perfectly still for extended periods, and Fitbit thinks she's taken a nap.