Sleep, Waste Clearance, and Dementia May Be Linked: Chronic stress, depression, cardiovascular disease, fragmented sleep, and aging are associated with a higher risk of dementia based on the same biological problem: disruption of a sleep-dependent brain rhythm that helps clear waste from the brain.
https://www.urmc.rochester.edu/news/story/the-brains-night-shift-how-sleep-waste-clearance-and-dementia-may-be-linked
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The Brain’s Night Shift: How Sleep, Waste Clearance, and Dementia May Be Linked
Why are conditions such as chronic stress, depression, cardiovascular disease, fragmented sleep, and aging all associated with a higher risk of dementia? In a new review piece in [*Science*](https://doi.org/10.1126/science.aeg2276), University of Rochester Medicine neuroscientist [Maiken Nedergaard, MD, DMSc](https://www.urmc.rochester.edu/labs/nedergaard), proposes that many of these seemingly different conditions may converge on the same biological problem: disruption of a sleep-dependent brain rhythm that helps clear waste from the brain.
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](https://www.urmc.rochester.edu/labs/nedergaard/projects/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.
https://www.science.org/doi/10.1126/science.aeg2276
The missing clearance stage can be mimicked by listening to a specific frequency (40 hz is what I remember) that then clears the auditory section of the brain. They did it with visual a few years later and found that the regions between visual and auditory were cleared when doing both protocols at the same time.
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C23&q=40hz+alzheimers&oq=40hz+#d=gs_qabs&t=1779563653821&u=%23p%3D4T9x-cjxAIYJ
There is so much overlap and bidirectional stuff going on here.
We know for a fact that exercise causally impacts brain health and is also causally linked to depression and dementia. Similarly there are links between sleep and diet with both depression and dementia.
So I would say that exercise, diet and sleep are the key factors causally linked to both depression and dementia. But I’m sure there might be some link from depression to dementia via behaviours.
Anyway the best and most effective things you can do to prevent or treat both depression and dementia are exercise, diet and sleep.
>brain rhythm that helps clear waste from the brain.
And the blood flow from exercise is also thought to help with this as well, plus it helps with sleep. But again it’s soo hard to disentangle things, since people who are night owls or have irregular sleep have terrible health habits as well.
>For the AD portrait, the top three scoring treatments for reversing AD expression with little effect on exacerbating AD expression were for exercise.
[https://www.nature.com/articles/s41598-022-22179-z#Sec2](https://www.nature.com/articles/s41598-022-22179-z#Sec2)
>Physical activity is 1.5 times more effective at reducing mild-to-moderate symptoms of depression, psychological stress, and anxiety than medication or cognitive behavior therapy, according to the study’s lead author, Dr. Ben Singh.
https://www.medicalnewstoday.com/articles/is-exercise-more-effective-than-medication-for-depression-and-anxiety
>Comprehensive lifestyle changes may significantly improve cognition and function after 20 weeks in many patients with MCI or early dementia due to AD.
[https://alzres.biomedcentral.com/articles/10.1186/s13195-024-01482-z](https://alzres.biomedcentral.com/articles/10.1186/s13195-024-01482-z)
>An online lifestyle intervention program aimed at improving diet, exercise and other modifiable risk factors for dementia has resulted in better cognition in older adults, Australian research has found.
[https://www.abc.net.au/news/health/2025-01-29/dementia-cognition-memory-clinical-trial-internet-brain-decline/104868518](https://www.abc.net.au/news/health/2025-01-29/dementia-cognition-memory-clinical-trial-internet-brain-decline/104868518)
Plus for dementia there is some evidence that the shingles vaccine helps.
>this study provides evidence of a dementia-preventing or dementia-delaying effect from zoster vaccination
>https://www.nature.com/articles/s41586-025-08800-x
Cool, so not only does my low paying shift work job keep me in a constant state of burnout and make me hate being alive, it’s gonna give me dementia too.