Something else to consider - what if the reason these plaques are unable to be cleaned out in some is the result of a life (decades)-long “deep” sleep deprivation (i.e, still getting sleep but not a good amount of regular, deep sleep where this cleaning process would normally occur), and the reason for this chronic sleep deprivation was some genetic pre-disposition, such as bruxism, which would cause little to no “deep sleep,” or perhaps brought on form of chronic dehydration due to a genetic predisposition for diabetes / sugary drinks / blood sugar imbalance, causing brain fogginess rather than deep sleep during a period of involuntary fasting, or a myriad of other unnoticeable deep- sleep-depriving illnesses?

I am not suggesting I have any answers; only questions and curiosities for the puzzling subject.