The researchers say their findings suggest sleeping in the lateral, or side position – as compared with sleeping on one’s back or stomach – appears to help the brain remove waste products more effectively and may thus reduce the chance of developing neurodegenerative diseases.
Increasingly, research is showing that sleep is important for brain health. Studies suggest that the brain is better at removing waste products when asleep than awake. And researchers are also discovering that poor sleep is linked to an increased risk of dementia.
For their study, the researchers focused on a complex system in the brain that clears away harmful substances that threaten to disrupt the normal function of cells and tissue.
The system – called the glymphatic pathway – filters cerebrospinal fluid (CSF) through the brain and exchanges it with interstitial fluid (ISF) to clear waste. The process resembles the lymphatic system that clears waste from organs in other parts of the body.
The glymphatic pathway is most efficient during sleep. It clears away potentially toxic chemicals from the brain – including amyloid beta and tau proteins. Build-up of these proteins is a known hallmark of Alzheimer’s disease.
The team used dynamic contrast magnetic resonance imaging (MRI) and computer modeling to measure CSF-ISF exchange in the brains of anesthetized rodents in three positions: lateral (lying on side), prone (lying on stomach) and supine (lying on back).
The analysis showed consistently that the glymphatic system was most efficient when the rodents were lying on their side than when they lay on their stomachs or on their backs.