How Deep Is Your Sleep?

Science Fields

We have all been in a situation where we had to pull an all-nighter to complete work projects, study, or travel. And we all know how it feels the day after. Fatigue, sleepiness, irritability, and forgetfulness are the fun consequences of sleepless nights.

Insufficient rest is not the only reason we experience these negative consequences. There is another reason; we did not give the brain the time necessary to activate its cleaning system by not sleeping. According to researchers from the University of Rochester Medical Center, the brain’s cleaning system, called the glymphatic system functions best when we are in non-REM deep sleep.  

Glymphatic system

The glymphatic system is similar to the lymphatic system in that it helps the brain to “wash away” toxic particles. The lymphatic system maintains fluid balance in the body, helps the immune system defend against bacteria and it is crucial for the absorption of fats and fat-soluble nutrients in the gut.

While we sleep, the brain turns on the glymphatic system to clean up harmful particles that are known to cause neurodegenerative diseases.

In a study they did in 2012, Dr. Jeffrey Iliff and colleagues found that the cerebrospinal fluid (CSF), a colorless fluid found in the brain and spinal cord, goes into the brain along special structures and exchanges with the fluid inside of the brain as it clears away waste. Dr. Iliff explains that CSF moves down the artery and into the brain tissue, ending up at the veins. There, it drains out of the brain and continues to flow through the arteries, brain tissue and veins to clear away waste.

Deep sleep is critical

Dr. Maiken Nedergaard and colleagues recently did a study on mice to observe the effects of six different anesthetic regimens on brain’s electrical activity, cardiovascular activity and flow of CSF.

They found that depth of sleep has an impact on the brain’s ability to wash away toxic proteins. Anesthetic regimens that most closely replicated the activity of non-REM deep sleep were ketamine and xylazine (K/X). The researchers observed that the glymphatic system functions most effectively when the brain waves are slow and steady. On the other hand, the mice in the study that were not exposed to anesthetic regimens that induced a deep-sleep state showed diminished glymphatic activity.

Implications for neurodegenerative disease

The current study sheds light on the link between sleep and dementia. According to the researchers, the accumulation of protein waste kills the neuronal network of the brain in neurodegenerative diseases. Moreover, the accumulation of the protein amyloid beta has been associated with Alzheimer’s disease for quite a while.

Thus it is important that the brain’s cleaning system functions properly since “more than half the amyloid removed from the brain of a mouse under normal conditions is removed via the glymphatic system.”

Findings from both studies suggest that the glymphatic system function can be manipulated using various sleep enhancing techniques such as sleep therapy. And the more attention we pay to our sleep now, the healthier we will feel in the future.  


  • 1. https://www.urmc.rochester.edu/news/story/5508/not-all-sleep-is-equal-when-it-comes-to-cleaning-the-brain.aspx
  • 2. https://www.urmc.rochester.edu/news/story/3584/scientists-discover-previously-unknown-cleansing-system-in-brain.aspx
  • 3. https://www.medicalnewstoday.com/articles/303087.php