Cleaning our brains during deep sleep

I monitor my sleep both with the Oura Ring and the Apple watch, and have observed that my mental clarity and feeling rested on waking positively correlates with the duration of my non-REM deep sleep. If it is 30 minutes or more I feel perky and rested, if 15 minutes or less, not so much. This made me note the review article in Brain magazine by by Hauglund and Nedergaard titled " Is glymphatic…