The glymphatic system flushes toxins out of the brain, but this seems to be disrupted in Alzheimer's disease, and cholesterol may be involved https://www.newscientist.com/article/2595089-cholesterol-may-disrupt-the-brains-cleaning-system-in-alzheimers-disease/?utm_term=Autofeed&utm_campaign=echobox&utm_medium=social&utm_source=Twitter#Echobox=1793011637