The glymphatic system – a vast arrangement of cerebrospinal fluid-filled cavities surrounding the small blood vessels in the brain – facilitates the removal of proteins and metabolites from the central nervous system. During sleep, these interstitial spaces increase by more than 60 percent. A new study demonstrates that large quantities of cerebrospinal fluid flow through these spaces in a rhythmic fashion during deep sleep to remove waste.
The study involved 13 young, healthy men and women whose neuronal activity, blood levels, and cerebrospinal fluid (CSF) flow were measured during sleep. As the study subjects slept, a large wave of CSF flowed through their brains roughly every 20 seconds, preceded by changes in brain neuronal activity and blood flow.
Poor sleep – which would impair glymphatic function – has been linked to a variety of neurodegenerative diseases. For example, disruption in deep sleep is highly pronounced in people with Alzheimer’s disease and typically precedes diagnosis.
Glymphatic activation has also been shown to play a key role in the transport of biomarkers of traumatic brain injury (TBI). In particular, cerebrospinal fluid-mediated removal of tau protein in the brain via glymphatic routes is crucial for limiting secondary neuronal damage following traumatic brain injury. Unfortunately, some types of TBI impair glymphatic function and may be one reason why people with TBI are at a higher risk for neurodegenerative diseases.
Taken together, these data suggest that sleep – especially deep sleep – is not only important for the prevention of Alzheimer’s disease but also may be key in the treatment of TBI.
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