Because a picture is worth a thousand words, and, honestly, because I am feeling too tired to do much of a write up on anything today… The sleep graphs from last night, starting with the fitbit.
And now the Zeo:
They’re pretty close on the amount of sleep; 12 minutes difference isn’t that much. And they match up on that 6 am waking. Sleep onset, they’re 8 minutes off of each other (I put the fitbit on two minutes after the Zeo, so it isn’t actually a ten minute gap). But, if you notice the movement shortly after sleep onset on the fitbit graph, it actually probably does match up. I just managed to lie still for a few minutes, which it’s interpreting as sleep onset.
The fitbit thinks I had several small wakings that the Zeo doesn’t register, and my own recollection agrees with the fitbit. However, Zeo tells you in their documentation that a waking has to last a certain amount of time in order to register. With the fitbit, all I have to do is twitch*. So that’s a difference in mechanism. I wouldn’t be surprised if you got similar results between an actigraph and an EEG in a sleep lab. But then, that’s why sleep labs use multiple measurement systems. It’s the cumulative data that gives you the whole picture.
Beyond that, the Zeo marks deep vs light vs REM sleep, which the fitbit can’t do (and doesn’t pretend to).
Thus far, both devices are living up to their promises.
*It is worth noting that a small twitch is not necessarily a full arousal. We tend not to move while sleeping, but that doesn’t mean we don’t move at all.