FitBit & EEG: how do they predict your sleep?

In this video I describe what sleep stages are, and how the FitBit and scientific encephalography (EEG) predict your sleep.
Traditionally sleep stages are measured by tracking your brainwaves using EEG devices. FitBits and other wearables say they can also predict your sleep, but how is that possible without measuring brainwaves? In this video I explain the process.

I also made a video that evaluates the accuracy of the sleep stage predictions that the FitBit makes. You can find it here: https://youtu.be/UAcasFNzUl8

This video is part of a larger project where I spend over 11 hours a week tracking everything in my life. If you’d like to know more, please subscribe to my channel for updates.

Note: When I am describing sleep, I am talking about what is considered average healthy sleep. People with sleep disorders or other sleep problems could show very different sleep patterns.
I am also not trained as a sleep expert. What I describe in this vlog, I have learned by talking with specialised scientists and reading scientific papers about the subject.