Maybe it's a bad idea to spend all night shit-posting on social media
By University of Rochester Medical Center
Edited by Sadie Harley,
reviewed by Robert
Egan
The article presents a new way of thinking about sleep, not
simply as a period of rest, but as a highly organized biological state that
coordinates brain chemistry, blood vessel movement, and cerebrospinal fluid
flow to support the brain's nightly cleaning process.
The piece also points to a potential biomarker, heart rate
variability, which can already be tracked with consumer wearables, as a simple,
noninvasive way to assess sleep-related brain health and identify people at
increased risk for cognitive decline.
"Sleep is not a quiet or inactive state," Nedergaard said. "During sleep, the brain shifts into a coordinated rhythm that appears to support one of its most important housekeeping functions."
Nedergaard's lab at URochester Medicine helped transform
neuroscience research in 2012 with the discovery of the glymphatic
system, a brain-wide network that circulates cerebrospinal fluid through
tissue surrounding blood vessels to help remove metabolic waste. The system is
especially active during sleep and has since become central to research into
Alzheimer's disease, Parkinson's disease, stroke, traumatic brain injury, and
other neurological disorders.
A synchronized sleep rhythm
The article focuses on neuromodulators—brain chemicals such
as norepinephrine, serotonin, dopamine, and acetylcholine that regulate mood,
attention, learning, and behavior during wakefulness.
These systems behave differently during non-REM
sleep, becoming synchronized into slow, repeating oscillations that occur
roughly every minute. These rhythms are linked to changes in brain activity,
heart rate, breathing, blood vessel movement, and cerebrospinal fluid flow.
"For decades, we thought about sleep primarily in terms
of memory and restoration," Nedergaard said. "What is emerging now is
the idea that sleep is also a highly organized fluid-transport state that helps
maintain brain health."
Sleep and the brain's cleaning system
These synchronized oscillations help power the glymphatic
system by driving slow rhythmic changes in blood vessel size known as
vasomotion. Those vascular movements, which are independent of the heart's
pumping action, help push cerebrospinal fluid through the brain and remove
waste products, including amyloid-beta and tau proteins associated with
Alzheimer's disease and other dementias.
Nedergaard argues that when these
rhythms are disrupted by aging, stress, psychiatric illness,
cardiovascular disease, poor sleep, or certain medications, the brain becomes
less efficient at clearing toxic proteins.
"Many disorders that increase dementia risk also
disrupt the brain's sleep rhythms," Nedergaard said. "Our work
suggests these may not be separate phenomena. They may be connected through the
brain's ability to clear waste during sleep."
A potential new biomarker
The article also highlights heart rate variability, subtle
changes in the timing between heartbeats, as a possible biomarker of
sleep-related brain health. Researchers found that heart
rate fluctuations during sleep appear closely tied to the same
neuromodulator rhythms occurring in the brain.
Nedergaard believes this could eventually provide a
noninvasive way to monitor the health of the brain's nighttime clearance system
and potentially identify people at increased risk for cognitive decline before
symptoms appear.
Publication details
Maiken Nedergaard, The oscillatory biology of sleep: Linkage
to dementia, Science (2026). DOI:
10.1126/science.aeg2276. www.science.org/doi/10.1126/science.aeg2276
Journal information: Science
