Her study found the glymphatic clearance was mediated by a hormone called norepinephrine and happened almost exclusively during the NREM sleep phase. But it only worked when sleep was natural. Anesthesia and sleeping pills shut this process down nearly completely.
I wouldn’t even call it common sense. I remember being taught like 20 years ago that we don’t even know for sure why we need to sleep (aside from the fact that we get tired and sleep is pretty good at helping with that).