Every 30 seconds, Dreem's machine learning algorithms determine what sleep stage you are in. The sum of these stages of sleep over a full night is the hypnogram that you can discover each morning on your app.
Extraction of data
100 values are extracted every 30 seconds from the different sensors of the Dreem headband (electroencephalogram, accelerometer, pulse oximeter). Among these values:
- the number of movements
- slow oscillations
- sleep spindles (or spindles), small bursts of fast rhythms, whose amplitude increases and decreases
- K complexes, characteristic waves of the transition from light sleep to deep sleep
Interpretation of your sleep stage
To more accurately define your sleep stages, the algorithm compares the 30-second epochs with a base of several hundred "scored" records by sleep specialists.
In order to put each 30-second epoch into context, we use the long short term memory (LSTM) model, which takes into account the history of the 20 preceding 30-second epochs analyzed in order to analyze the current epoch. The model will consider for example the fact that you have been in deep sleep for a few minutes to analyze the current epoch.