I’ve read a lot about sleep, along with many articles that try to explain why we need sleep.  In my mind, the primary purpose of why sleep is necessary is to clear brain waste.

Watch this TED Talk …

The waking brain is highly metabolically active and uses 20% of the oxygen supply.  As part of its waste by-product is Amyloid beta.  Yes, the sticky plaque that is found in Alzheimer’s patients.

In order to clear out this amyloid beta and other waste or toxins, the brain does not have a lymphatic system like the other organs.  Instead it has a glymphatic system.

Some videos showing how the glymphatic system at work …

and …

NPR.org has a couple of audio programs on this …

Brains Sweep Themselves Clean Of Toxins During Sleep (audio program available)

Lack Of Deep Sleep May Set The Stage For Alzheimer’s (audio available)

Alzheimer’s patient have been found to have more sleep problems.  And it may be that the sleep problems is partly what caused the Alzheimer.  People with sleep problems also have higher amyloid beta.

The problem with the glymphatic system is that it only works during sleep.  This is when brain cells shrink in order for CSF (cerebral spinal fluid) to wash out the waste. They found this out with mice models. During the day, the brain is to metabolically active.

So if you don’t sleep, your brain can not clear out waste.   Or if you don’t sleep enough, your waste removal may get back-logged and beta amyloid plaques may accumulate.

We now know that concussions and brain trauma can increase risk of Alzheimer’s many years later.  It may be that these injuries damages the glymphatic system so that brain can not clear beta amyloid efficiently.