Researchers from the University of Rochester Medical Center have concluded that sleep is vital for the brain’s “cleansing” process, removing toxic substances linked to dementia development. A review of relevant studies was published in the journal Science.
The scientists explained that during sleep, the brain doesn’t shut down but rather enters a distinct operational mode. In this phase, the activity of nerve cells, breathing patterns, heart rate, and the flow of cerebrospinal fluid become synchronized. This synchronization activates the glymphatic system, a mechanism responsible for clearing metabolic byproducts and harmful proteins from the brain.
According to the researchers, it is primarily during sleep that the brain most effectively eliminates amyloid and tau proteins – substances whose accumulation is associated with Alzheimer’s disease and other forms of dementia. When sleep quality deteriorates or becomes fragmented, this cleansing system operates less efficiently.
The study authors suggest that this might explain why chronic stress, depression, cardiovascular diseases, aging, and persistent sleep deprivation increase the risk of cognitive impairment. All these conditions disrupt the brain’s nocturnal rhythms, hindering the normal removal of toxins.
Furthermore, the investigators identified a potential early indicator of such issues: heart rate variability during sleep. This metric can already be measured by many smartwatches and fitness trackers. In the future, these devices could assist medical professionals in identifying dementia risk even before the onset of initial symptoms.
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