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So biological garbage collection pauses then? skip sleep, and the brain tries to run gc cycles during runtime. Causing attention and performance latency spikes. Evolution wrote the original JVM.

I hope that the actual medical field starts taking note of this.

My wife still has to work 24 hour shifts with no sleep, performing emergency surgeries no matter how long it has been since she slept. During residency only a few years ago she and her co-residents were almost weekly required to do 36 hour shifts (on top of their regular 16 hours per day, 5 day per week schedule) and once even a 48 hour shift when the hospital was short staffed.

Of course I’m sure they won’t. No one cares if doctors are over worked.

> The scientists found that during these lapses, a wave of cerebrospinal fluid (CSF) flows out of the brain

> Lewis and colleagues showed that CSF flow during sleep follows a rhythmic pattern in and out of the brain

> Most significantly, they found a flux of CSF out of the brain just as those lapses occurred. After each lapse, CSF flowed back into the brain.

I can't believe the authors of the article didn't address one of the most obvious questions: Where does the CSF flow to and where does it flow back from? It's not like there are pipes leading out of the brain, or the CSF will just leave my brain through my ears or anything, will it?¹ What happens with the waste products? (¹ Though it would be kinda funny if this was where snot comes from.)

EDIT: Wikipedia's got the answer:

> Clearing waste: CSF allows for the removal of waste products from the brain,[3] and is critical in the brain's lymphatic system, called the glymphatic system. Metabolic waste products diffuse rapidly into CSF and are removed into the bloodstream as CSF is absorbed. When this goes awry, CSF can become toxic […]

https://en.wikipedia.org/wiki/Cerebrospinal_fluid

Long live healthy sleep for brain health, and thank goodness light exercise helps this same glymphatic system.

What I want to know is: can we trigger these flushes? My grandfather died of/with Alzheimer’s, and I’d prefer not to follow in his footsteps. If we determine that these flushes are key to good brain health, and there were a way either through a pill or even a treatment to up the frequency of these flushes, that would be awesome.

Rest in peace to all the college dudes covering the whole syllabus within 24 hours of the exam

So... can we trigger it manually? I'd love to be able to lay down and press the 'flush brain' button.

I slept around 5 hours last night split up into two periods because my baby daughter woke up crying from fever and wanted to play / was hallucinating / etc. She's totally fine now but I am wondering if there is a correlation between dementia and having kids.

What I’m picking up here is that if I can just get an automated CSF circulator installed I won’t need to sleep or get distracted when I’m tired. That was the point of this article, right?

Could ADHD be caused by a broken flushing response? Lots of flushing followed by intense focus caused by the tabula rasa?

I wonder if a 30-min nap improves the situation. But I need to tell the brain to hold the flushing until the nap.

I wonder if this could help explain why creatine helps mitigate the effects of sleep deprivation. Since creatine aids in water retention.

https://pubmed.ncbi.nlm.nih.gov/16416332/

Exogenous ketones (such as BHB salts) are known to help with glymphatic drainage in the brain during sleep. I've used them extensively and have noticed improved sleep with nearly a doubling of the time spent in REM stage.

That is very interesting. I have a somewhat related issue with sleep cycles. This issue, waking around 3:00am every morning then not going back to sleep until 6 or 7am, is not really a productive sleep cycle. I read somewhere that taking a spoon of sugary substance, like Raw Honey, MCT or Collagen, before going to bed can replenish the brain of this energy, so it becomes easier to fall asleep. I've been trying it with two to three spoons of honey, right before hitting the sack to see if it can help me fall asleep again. It seems to be having a somewhat positive effect as it does not take me too long to go back to sleep.

In high school a friend of mine told me about "microsleep" and how your brain will oscillate into it if you're under-rested. This would align with that theory.

Wikipedia has a nice moving MRI of the flushing https://en.wikipedia.org/wiki/Cerebrospinal_fluid#Circulatio...

Good to know that the brain finds a way to flush itself while awake. I think I've become pretty good at putting unused parts of my brain to sleep while awake. My brain is like that of a dolphin now.

But on rare occasions (like a couple of times a year), I get migraine auras and stuff disappears from my field of view. Can last about an hour. I feel like that's my visual cortex falling asleep.

My pet theory is that dreams are the brain booting up/shutting down and the equivalent of old analog TVs that have the flash of static and bloom/collapse on the screen when turning off/on.

Sometimes when I get a really bad migraine and poor sleep together, I can literally feel a flushing feeling in my head once I can fall asleep.

Maybe unrelated but, years ago, I had a job that had me criss-crossing the country by plane Monday through Friday and sometimes Saturday. So my sleep and the time zones and hotels could sometimes mess with me.

One day, I went to a grocery store and mid-turn onto another street, I forgot what city I was in. Worse, I was half a mile from my apartment in my home town.

Back when I used to meditate regularly, I would find that an extra meditation in the middle of a sleepless night would go a long way toward pushing off the need for sleep. Generally, meditating always left me in a slightly heightened awake state. Perhaps the help with brain fluid regulation is a core reason for both effects. (I should go back to meditating again.)

This is fascinating, and somewhat directly related to the work we do increasing slow-wave response during sleep.

For those who are not aware, slow-wave are the hallmark of deep sleep and closely linked to the flushing the glymphatic system, which is what they are referring to in this article.

We can't create slow-waves, but we can increase their effectiveness through precisely timed auditory stimulation. I'll be posting a Show HN next week which dives into the data of how this works, but if you want to know more, there is info on our website and links to over 50 published peer-reviewed papers. https://affectablesleep.com

This paper specifically looks at amyloid clearance as a result of this glymphatic flush https://doi.org/10.1093/ageing/afad228

While many people will point to "getting more sleep" that isn't really the answer. More time asleep does not automatically mean increased glymphatic flush. Additionally, as we age, the power of the pump gets weaker, and more sleep does not help with that.

We believe the focus on counting minutes of sleep misses the point of what makes sleep truly restorative and beneficial, which are the neurological processes, and downstream physiological changes as a result. This is why we talk about restorative function, and that should be the focus of sleep health, not time.

After all, you wouldn't measure your diet based on how much time you spend chewing, would you?

hmm.. this is interesting... the article says "spinal fluid exits the cerebrospinal fluid (csf) flows out of the brain... I wonder where it discharges these waste products. I ask because it is believed we have a sort of chimney on our backs. I think I read this on the article of the Irish lady who could detect alzheimers years before any modern medical detection systems. But maybe it is discharged in the gut? via the mesentery, the new organ they finally named fo rthe stuff that holds our intestines together. If anyone knows where it is discharged, please comment, I'm interested in this, because I do prolong waterfasts every 3 months, and I strongly believe the brain drains waste into my mouth during that time, because the taste in my mouth is godawful, but if there are other exit points the brain discharges waste, we probably need to know about them.

anecdotally, i never feel better than when i haven't slept. spent 8pm tuesday -- 8pm thursday this week awake nursing cheap energy drinks, and not only could i manage a higher-than-usual level of focus, i was genuinely content.

bombed a midterm halfway though, but at least i felt good about it.

> For example, what you don't want to do is NOT take amphetamines at testing if you had used them to study;

Hard disagree there. If you get any anxiety during the test it's better to take it only while studying.

[This is one of those article titles that would really benefit from adding one more word.]

Could this be why SNRIs help some patients mitigate ADHD symptoms?

I can feel when this fluid hasn't properly flushed.

Need a cron job to flush that cache

As a chronic undersleeper, good thing I don't drive!

Sleep is indeed important

should have given them a cup of joe while in the fmri to see what difference that made

This reminds me of delirium tremens a bit. Same compensatory mechanism, different sleep process - or at least that's the pattern I'm seeing.

The MIT study shows CSF waves—normally a sleep-only process that flushes metabolic waste—intruding into wakefulness when you're sleep-deprived. Your brain is apparently so desperate for the cleanup that it forces the process to happen anyway. Cost: attention lapses.

From what I've read, delirium tremens during alcohol withdrawal seems to follow a similar pattern, except it's REM sleep intruding into waking consciousness instead of CSF flushing.

[Polysomnographic studies from the 1960s-80s](https://pubmed.ncbi.nlm.nih.gov/7318677/) documented this. Patients in alcohol withdrawal exhibit what researchers call ["Stage 1-REM"](https://www.sciencedirect.com/topics/neuroscience/delirium-t...)—a hybrid state where wakefulness and REM sleep characteristics get mixed together. Right before full-blown DTs, [some patients hit 100% Stage 1-REM](https://link.springer.com/chapter/10.1007/978-1-4757-0632-1_...). The hallucinations appear to be [literally enacted dreams](https://www.sciencedirect.com/science/article/abs/pii/S01651...) occurring while technically awake. The sleep-wake boundary just completely breaks down.

What strikes me is the system-level similarity here. Sleep normally maintains clean states: you're either awake (alert, reality-testing intact, no CSF flushing) or asleep (offline, dreams permitted, maintenance running). But when the system gets stressed enough—whether through sleep deprivation or the neurochemical chaos of alcohol withdrawal—it seems to start making desperate tradeoffs.

The brain apparently needs certain processes to run. Period. Total no-brainer! CSF flushing can't wait indefinitely. Neither can REM sleep, which serves its own critical functions. So when normal sleep architecture fails, the system appears to force these processes anyway, even though the conditions are completely wrong for them.

Maybe that's why the costs are so specific. CSF intrusion during wakefulness costs you attention. REM intrusion costs you reality testing, because REM is the state where your brain accepts impossible narratives without question. Same compensatory mechanism, different critical process forced into the wrong state.

What I find interesting is how the brain knows what lever it needs to pull and how it pulls it. Sleep deprivation forces waste removal. REM deprivation forces wakeful dream states; which might be a side effect not the actual goal. The brain seems to know what maintenance is overdue and attempts the repair, consequences be damned.

Title sucks