It’s common knowledge that sleep is important for health and wellness, but why? We’ve known for decades that REM sleep helps the brain with learning and memorization of things. We’ve also known that REM’s lesser-known sibling Non-REM (insanely creative, I know) is crucial for helping the body regulate itself and restoring tissue.
But in recent years, we’ve also learned that sleep can play a key role in preventing degenerative neurological conditions like Alzheimer’s and other forms of dementia. Why is this? Let’s get into the nerd science!
The brain has a glymphatic system which is responsible for carrying toxins out of the brain. The name is a portmanteau of glial (a kind of nerve cell) and lymph (the fluid which circulates and drains various substances in the body). The glymphatic system is a very new concept- first described in 2012. You may have heard of the blood-brain barrier- it’s not easy to get things in or out of the brain. The only substance that passes between the brain and the rest of the body is cerebral spinal fluid (CSF). What we’ve learned is that there’s a plumbing system in the brain which circulates CSF and it’s this system which helps get rid of dead cells and other toxins.
What kind of toxins? You may have heard of two key ones- beta amyloid and tau proteins, considered to be the substances which form plaques producing the symptoms of Alzheimer’s.
Research has also found that this brain self-cleaning system works best when we are asleep (specifically in deep NREM sleep also known as “slow wave sleep.” During slow wave sleep, the neurons of the brain fire rhythmically and synchronously. Here’s a pretty picture of that- note how they brain waves (in black) all follow a similar pattern.
The cool thing is those waves you see on the EEG (electroencephalograph) are more than a description of electrical energy. It is now thought that they also correspond to undulations of the CSF through the glymphatic pathways. In other words, when the neurons fire in synchrony during deep sleep, they are actually creating mechanical movement to push out toxins! Specifically, when the neurons all fire ‘off’ at once, they seem to create a space for CSF to rush into the brain. When they fire back “on,” they then create a pumping action to move the fluid along.
As sleep deprivation has been associated with increased risk for Alzheimer’s disease, this make sense. Additionally, when we age, we naturally sleep less so it could also mean that as our sleep drive drops over time, our risk for dementia can increase.
What does this mean in practical terms? Certainly it reinforces the need to make sleep a priority for your long-term health and to help in aging gracefully. If you’re having issues sleeping, we have many other resources on our website in prior blogs and in our Sleep Coaching section to help. For those who already have dementia, perhaps this new insight will help scientist find ways to capitalize on the glymphatic system to help remove some of the bad stuff clogging up the brain and impeding clear thought and concentration. As the daughter of a patient with dementia, we can only hope!
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