Sleeping on one's side, as opposed to other positions such as on one's back or stomach may more effectively remove brain waste, reducing the chances of developing Alzheimer's, Parkinson's and other neurological diseases, scientists have found.
Researchers at Stony Brook University 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.
Researchers Hedok Lee, Helene Benveniste and colleagues, discovered that a lateral sleeping position, or side 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.
Benveniste, Principal Investigator and a Professor in the Departments of Anesthesiology and Radiology at Stony Brook University School of Medicine, has used dynamic contrast MRI for several years to examine the glymphatic pathway in rodent models.
The method enables researchers to identify and define the glymphatic pathway, where cerebrospinal fluid (CSF) filters through the brain and exchanges with interstitial fluid (ISF) to clear waste, similar to the way the body's lymphatic system clears waste from organs.
In the new study, Benveniste and colleagues used a dynamic contrast MRI method along with kinetic modelling to quantify the CSF-ISF exchange rates in anesthetised 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 Benveniste.
"Because of this finding, we propose that the body posture and sleep quality should be considered when standardising 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," said Benveniste.
"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," said Maiken Nedergaard at the University of Rochester.
"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," she said.
