Glymphatic System and NREM Sleep

A growing body of literature that suggests that sleep deprivation and sleep disorders can independently contribute to the development of cognitive impairment and dementia. While the role of sleep in humans in not completely understood, it is clear that it serves at least several important restorative or housekeeping functions. One of these housekeeping tasks involves the flushing of inter-neuronal debris from the brain. This occurs during adequate amounts of deep sleep. During deep sleep, metabolic waste products including adenosine, a signal for sleepiness, are removed from the brain. Slow wave or Non-rapid-eye-movement-sleep (NREM) is a state of deep usually dreamless sleep that occurs regularly during a normal period of sleep. This deep NREM sleep with delta waves is controlled by serotonin cells in the brainstem and restores energy and eliminating feelings of fatigue. It also  seems to enhance the activity of the glymphatic system by about 60%.