“I just want to say one word to you. Just one word. Glymphatics.”

In this, the 21st century, the century of the brain, the one word that we need to pay attention to is no longer Plastics, but it could very well be Glymphatics.  A network of fine vessels in the peripheral organs, including our limbs, carries that fluid that gets exuded from our blood back into the venous system and the heart.  A corresponding system in the brain may be the recently discovered Glymphatics.  The Glymphatic system surrounds the blood vessels that enter the brain and may be the plumbing system that drains metabolic wastes away from active brain tissue.  What forces drive the flow of Glymphatic fluid in the brain – it is mainly driven by the pulsatility of the arterioles that act like a pump, driving the flow of Glymph around the small arteries in the brain.  Further convective flow of Glymph through the brain tissue (the space between the nerve cells) and back into the space surrounding the veins that drain the brain is driven by respiration (the negative pressure generated in the chest during inspiration may provide a pressure sink that convectively draws Glymph from the brain into the veins).  What does this have to do with Sleep?

Interestingly, it is during sleep that Glymphatic flux is at its highest.  Indeed, during sleep, there is an expansion of the Glymphatic fluid volume.  Since Glymph carries toxic wastes along with it out of the brain, it appears that a key function of Sleep may be to promote this clearing process that helps the brain rid itself of wastes that have accumulated during the metabolically hyperactive waking state.  The state of quiescence during sleep also allows this cleaning process to be undertaken without disturbing that active mentation that is required by us when we are awake.

Age and sleep-loss decrease Glymph flux.  This may account for the accumulation of wastes and the triggering of neurodegenerative changes in the brain due to the accumulated toxins.  On the contrary, enhanced Sleep may serve as a protective mechanism that clears out these toxins when we sleep.

If the Glymphatics prove to be as important to brain health as data is starting to show, you may well want to give your kids the advice contained in the title to this piece.  Getting good sleep may be the practical implementation of this advice.

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