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Not All Sleep is Created Equal

You may think that making sure you get plenty of sleep is enough, but new research shows that HOW you sleep is also important. 

The study, conducted at the University of Rochester Medical Center (URMC), shows how the depth of sleep can impact our brain’s ability to efficiently wash away waste and toxic proteins. Because sleep often becomes increasingly lighter and more disrupted as we become older, the study reinforces and potentially explains the links between aging, sleep deprivation, and heightened risk for Alzheimer’s disease.

“Sleep is critical to the function of the brain’s waste removal system and this study shows that the deeper the sleep the better,” said Maiken Nedergaard, M.D., lead author of the study. “These findings also add to the increasingly clear evidence that quality of sleep or sleep deprivation can predict the onset of Alzheimer’s and dementia.”

The study indicates that the slow and steady brain and cardiopulmonary activity associated with deep non-REM sleep are optimal for the function of the glymphatic system, the brain’s unique process of removing waste. The findings may also explain why some forms of anesthesia can lead to cognitive impairment in older adults.

The previously unknown glymphatic system was first described by Nedergaard and her colleagues in 2012. Prior to that point, scientists did not fully understand how the brain, which maintains its own closed ecosystem, removed waste. The study revealed a system of plumbing which piggybacks on blood vessels and pumps cerebral spinal fluid (CSF) through brain tissue to wash away waste. A subsequent study showed that this system primarily works while we sleep.

Because the accumulation of toxic proteins such as beta amyloid and tau in the brain are associated with Alzheimer’s disease, researchers have speculated that impairment of the glymphatic system due to disrupted sleep could be a driver of the disease. This squares with clinical observations which show an association between sleep deprivation and heightened risk for Alzheimer’s.

The study raises several important clinical questions. It further bolsters the link between sleep, aging, and Alzheimer’s disease. It is known that as we age it becomes more difficult to consistently achieve deep non-REM sleep, and the study reinforces the importance of deep sleep to the proper function of the glymphatic system. The study also demonstrates that the glymphatic system can be manipulated by enhancing sleep, a finding that may point to potential clinical approaches, such as sleep therapy or other methods to boost the quality of sleep, for at-risk populations.

Source: News Release