There is nothing quite like waking up in the morning feeling refreshed and cognitively sharp with optimal mental clarity and focus. Recent research has revealed the mechanism that clears the mind of neurotoxins while you sleep, a process that plays a major part in healthy cognitive function.

The Glymphatic System

In 2012 scientists discovered the ‘glymphatic’ system, a previously unknown waste clearance system in the brain(1). Once you are asleep your glymphatic system kicks into overdrive and actively flushes out waste from every corner of the brain. Scientists have found that your glymphatic system is largely disengaged when you are awake with lead researcher, Maiken Nedergaard commenting:

“You can think of it like having a house party. You can either entertain the guests or clean up the house, but you can't really do both at the same time” (2) Maiken Nedergaard, M.D., D.M.Sc.

During sleep, the glymphatic system circulates cerebrospinal fluid through the brain by flushing the channels around the arteries removing waste. This process clears out neurotoxins including Amyloid beta. Amyloid beta plays a major role in the development of Alzheimer’s(3). Even just one night of sleep deprivation can cause an accumulation of Amyloid beta in the brain(4), showing the importance of adequate sleep for your brain health and function.

Further research is needed into exactly how much sleep you need for your glymphatic system to function well, however a 2018 study did look at which sleeping positions were best for this crucial neurological process. Interestingly researchers found that your glymphatic system operates best when sleeping on your side(5). The researchers noted that lateral or side sleeping has evolved to be the most common sleep position in humans and animals.

Why sleep matters to your brain

As well as clearing out waste, sleep also plays a crucial role in promoting good mental health, with a recent study in the British Medical Journal stating that “..sleep is now thought to have a bidirectional relationship with mental health, with problems sleeping likely to influence both the onset and trajectory of a variety of mental health difficulties”(6).

Sleep plays a critical role in learning and your ability to complete complex cognitive tasks(7). There are multiple studies that show the consolidation of memories takes place while you sleep(8). with the ‘REM’ and Slow Wave Sleep (SWS) stages of sleep both playing a role(9). This includes your memory of how to complete a new physical task. Recent studies have also shown that sleep is a requirement for the brain to be able to reorganise, which is known as ‘plasticity’(10).

From a neurological perspective the five key functions of sleep are:

  1. Allow your brain to clear waste products (including Amyloid beta)  
  2. Prevent neurological decline (Dementia, Alzheimer’s, Parkinson’s and other neurological disorders)
  3. Promote good mental health
  4. Aid Memory and learning
  5. Wake up with a clear mind feeling refreshed and cognitively sharp


We offer a bespoke sleep coaching service if you need further support in this important area of your health.  If you are interested in exploring your personal sleep challenges including testing melatonin and cortisol levels then please get in touch on our contact page for more information.   

1. Scientists Discover Previously Unknown Cleansing System in Brain

2.  Study reveals brain ‘takes out the trash’ while we sleep

3. β-amyloid Peptides and Amyloid Plaques in Alzheimer’s Disease

4. β-Amyloid accumulation in the human brain after one night of sleep deprivation

5. The Effect of Body Posture on Brain Glymphatic Transport 

6. Does improving sleep lead to better mental health? A protocol for a meta-analytic review of randomised controlled trials 

7. Sleep Accelerates the Improvement in Working Memory Performance 

8About Sleep's Role in Memory 

9. Mechanisms of Memory Retrieval in Slow-Wave Sleep 

10. Sleep, memory, and plasticity.