Sleep loss is often one of the most challenging symptoms of dementia and Alzheimer’s, affecting patients long before memory loss and a formal diagnosis is made. New research from the University of Kentucky has likened poor sleep to a canary in a coal mine, an early symptom of neurodegeneration that could serve as a potential new biomarker to identify the disease.
Researchers have long known that tau protein plays a central role in Alzheimer's disease, but a new study reveals a surprising twist: rather than simply depleting the brain's energy supply, tau buildup may actually preserve it — while quietly tipping the brain's chemical balance toward dangerous over-excitement. The findings suggest that tau steers glucose away from calming, inhibitory processes and toward fueling runaway neural activity.
As a result of this changing chemistry, the brain remains overly active rather than transitioning into the synchronized, restorative rhythms needed for normal sleep, study author Riley E. Irmen explained in an interview. This suggests sleep is not just a side effect of Alzheimer’s but may be part of the disease process itself, with poor sleep acting as an early warning sign that shows up long before classic cognitive symptoms.
“When somebody is awake, their brains are more active and can overproduce toxic proteins, while deep sleep helps quiet the brain, supports restorative processes, and clearance of metabolic waste,” explained Irmen. “When sleep becomes fragmented, that balance may tilt in the wrong direction to too much activity and not enough clearance and quiet. At this stage, sleep is best thought of as a promising biomarker and risk signal, not a standalone diagnostic test.”
Earlier work has revealed that Alzheimer’s disease involves a breakdown in the brain’s energy system, creating a vicious cycle in which the disease causes sleep disruption, and poor sleep further accelerates the disease. Previous research has also suspected that disrupted sleep could be an early indication of Alzheimer’s disease.
The new study adds to this body of work by observing the way tau is involved in hijacking the brain’s fuel supply, driving it into a state of constant overdrive, and creating an imbalance between stimulatory and calming signals.
Engine trouble
Because researchers believe the brain’s “engine” is misusing fuel during this process, some of these effects may be reversible, suggesting that the pattern could be interrupted with existing drugs, a theory that’s been supported by other studies.
“Our study points to the idea that existing drugs which restore inhibitory tone or rebalance sleep-related brain activity could potentially ease some symptoms associated with Alzheimer’s,” explained Irmen. “Targeting sleep and excitability may be a practical way to reduce downstream harm, restore sleep, and precisely target the brain circuits that are disrupted.”
The researchers will next build upon these findings and believe that, until a cure is found, targeting lifestyle-related risk factors, such as sleep and metabolism, can reduce vulnerability to disease or potentially slow progression. “That’s what these studies lay the groundwork for,” Irmen said.
“The paper gives some evidence that sleep has early-stage biomarker potential, as the sleep change may be measurable years before cognitive symptoms,” said Timothy Hearn, assistant professor in the Department of Medical Genetics at the University of Cambridge, who was not involved in the study. “Small losses of slow-wave or REM sleep could indicate stress caused by … tau long before atrophy would appear on an MRI.”
Hearn said that, as the findings come from transgenic mice, human confirmation would be essential as a next step. “Whether correcting sleep and metabolism will slow cognitive decline remains to be demonstrated in longitudinal trials,” he also added.
The study has been published in NPJ Dementia.
Fact-checked by Mike McRae
