Sleep’s nightly cleaning cycle linked to dementia risk, new science suggests

A Science review from University of Rochester researchers argues that sleep is a highly organized brain-cleaning state. Sleep-dependent brain rhythms coordinate vascular movement and cerebrospinal fluid flow to power the glymphatic system, which clears waste like amyloid-beta and tau. Disruptions from aging, stress, depression, cardiovascular disease, fragmented sleep, or certain medications may impair this clearance, helping explain why these conditions raise dementia risk. The piece also highlights heart-rate variability during sleep as a potential noninvasive biomarker to assess brain health and identify people at higher risk before cognitive symptoms appear.