In terms of the sleep we currently capture with Biostrap, light sleep is what we are characterizing as stages 1 and 2 in clinical terms. Deep sleep is stages 3 and 4. 

For more information on these stages, we recommend the website www.sleep.org

Biostrap currently classifies REM  under "deep" sleep.

We will be tracking REM separately in an upcoming app version, due early 2020.

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