A new review in Science by University of Rochester neuroscientist Maiken Nedergaard argues that disruption of a sleep-dependent brain rhythm could help explain why diverse conditions raise dementia risk.
Nedergaard frames sleep not simply as rest but as a coordinated biological state that synchronizes neuromodulators (norepinephrine, serotonin, dopamine, acetylcholine), slow brain oscillations during non-REM sleep, breathing, blood-vessel movement and cerebrospinal-fluid (CSF) flow. Those coordinated rhythms, the review says, drive vasomotion—slow changes in vessel diameter independent of the heartbeat—that help push CSF through brain tissue and clear metabolic waste such as amyloid-beta and tau.
“Sleep is not a quiet or inactive state,” Nedergaard is quoted as saying. Her lab first described the glymphatic system in 2012; that pathway, which is more active during sleep, has since been central to research into Alzheimer’s, Parkinson’s, stroke and traumatic brain injury.
The review links disruptions in the sleep-linked rhythm to conditions already known to raise dementia risk: aging, chronic stress, depression, cardiovascular disease, fragmented sleep and some medications. “Many disorders that increase dementia risk also disrupt the brain’s sleep rhythms,” Nedergaard says. “Our work suggests these may not be separate phenomena.”
The article also highlights heart rate variability (HRV)—small beat-to-beat timing changes measurable by consumer wearables—as a candidate noninvasive biomarker. The review notes that HRV fluctuations during sleep appear tied to the same neuromodulator-driven rhythms in the brain, and could potentially flag reduced nighttime clearance before cognitive symptoms emerge. The paper presents this as a research direction rather than an established clinical tool.
The review reframes sleep-linked clearance as a common biological node connecting several dementia risk factors and points to wearable-tracked HRV as a practical signal to study in longitudinal and clinical cohorts.
Photo credit: www.futurity.org
Tags: sleep, glymphatic system, heart rate variability, dementia, biomarkers
Topics: Neuromodulation, Wearable neurotech, Sleep technology