Sleep unlocks brain's toxin-cleaning system, scientists say

A review published in Science argues that sleep drives a brain-cleaning process via the glymphatic system that clears waste such as amyloid-beta and tau. This flow is coordinated by shifts in neuromodulators and heart-rate variability, potentially detectable with smartwatches, and could signal brain health risks. The work reinforces sleep as essential for preventing dementia, though more human studies are needed to confirm how sleep disruption contributes to disease and to explore future therapies.