Body Posture In Sleep May Affect How Your Brain Clears Waste

Sleeping in the lateral position (on your side), compared to sleeping on your back or stomach, could more effectively remove brain waste and turn out to be a good practice to help lower the chances of developing Parkinson’s, Alzheimer’s, and other neurodegenerative diseases, according to research from Stony Brook University.

In humans and many animals the lateral sleeping position is the most common one.

Researchers Hedok Lee, PhD, Helene Benveniste, MD, PhD, and colleagues used dynamic contrast magnetic resonance imaging (MRI) to image the brain’s glymphatic pathway, a complex system that clears wastes and other harmful chemical solutes from the brain.

The results showed that a lateral sleeping position is the best position to most efficiently remove waste from the brain. The buildup of brain waste chemicals may contribute to the development of Alzheimer’s disease and other neurological conditions.

The Glymphatic Pathway

The glymphatic pathway filters cerebrospinal fluid (CSF) through the brain and exchanges it with interstitial fluid (ISF) to clear waste, similar to the way the body’s lymphatic system clears waste from organs. It is during sleep that the glymphatic pathway is most efficient.

Brain waste includes amyloid β (amyloid) and tau proteins, chemicals that negatively affect brain processes if they build up.

Dr. Benveniste’s team used dynamic contrast MRI along with kinetic modeling to quantify the CSF-ISF exchange rates in anesthetized rodents’ brains in three positions; lateral (side), prone (down), and supine (up).

“The analysis showed us consistently that glymphatic transport was most efficient in the lateral position when compared to the supine or prone positions,” said Dr. Benveniste. “Because of this finding, we propose that the body posture and sleep quality should be considered when standardizing future diagnostic imaging procedures to assess CSF-ISF transport in humans and therefore the assessment of the clearance of damaging brain proteins that may contribute to or cause brain diseases.”

The researchers’ colleagues at the University of Rochester, including Lulu Xie, Rashid Deane and Maiken Nedergaard, PhD, used fluorescence microscopy and radioactive tracers to validate the MRI data and to assess the influence of body posture on the clearance of amyloid from the brains.

“It is interesting that the lateral sleep position is already the most popular in human and most animals — even in the wild — and it appears that we have adapted the lateral sleep position to most efficiently clear our brain of the metabolic waste products that built up while we are awake,” says Dr. Nedergaard. “The study therefore adds further support to the concept that sleep subserves a distinct biological function of sleep and that is to ‘clean up’ the mess that accumulates while we are awake. Many types of dementia are linked to sleep disturbances, including difficulties in falling asleep. It is increasing acknowledged that these sleep disturbances may accelerate memory loss in Alzheimer’s disease. Our findng brings new insight into this topic by showing it is also important what position you sleep in.”

Though the research team believes that the human glymphatic pathway will also clear brain waste most efficiency when sleeping in the lateral position as compared to other positions, verification with MRI or other imaging methods in humans is necessary.

[thrive_text_block color=”light” headline=””]Hedok Lee, Lulu Xie, Mei Yu, Hongyi Kang, Tian Feng, Rashid Deane, Jean Logan, Maiken Nedergaard, and Helene Benveniste.
The Effect of Body Posture on Brain Glymphatic Transport.
Journal of Neuroscience, July 2015 DOI: 10.1523/JNEUROSCI.1625-15.2015
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