Sleep does not help brain wash out toxins, study suggests | Hacker News Reader

Sleep does not help brain wash out toxins, study suggests

theguardian.com

44 pointsisaacfrond30 comments

At this point most of my cerebrospinal fluid is replaced with coffee, so I don't know what my brain is supposed to clear out during sleep.

thanks for the reminder to start brewing cup no 3

Obviously the article leave a lot of the science out, but this sounds like it’d be an easy thing to test for (which they’ve now done). Why wouldn’t this have been done years ago - I’m not trying g to say they should have done it earlier, as I genuinely don’t know. Is the tech to check this new? How much other science has been based off of this theory in the meantime?

Did they test it succesfully? Did they make some blunder? Did they misrepresented the importance of their results? Will it replicate? Does it apply to humans?

I wouldn't be bothered with putting much faith on any of the papers coming out, unless I was a researcher in that space. The dust is far from settled.

Oh me neither, I’m less interested in the results and more that (to someone who has no idea behind the science - me), I’m surprised to hear it’s just now only being tested when I’ve heard this was the main theory of sleep for years.

What about this, from a month ago: https://arstechnica.com/science/2024/04/sleeping-more-flushe...

Which seems to very clearly show that the brain flushes things out when we're asleep.

It doesn't show that.

All your article says is that neuron trigger the gylmphatic system to create waves.

It doesn't establish that the waves actually remove more waste product.

It doesn't even actually establish that the waves cause more flow. They are simply a "plausible mechanism to explain the correlated flow".

What about this?

Sleep Drives Metabolite Clearance from the Adult Brain (2014)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3880190/

> Using real-time assessments of tetramethylammonium diffusion and two-photon imaging in live mice, we show that natural sleep or anesthesia are associated with a 60% increase in the interstitial space, resulting in a striking increase in convective exchange of cerebrospinal fluid with interstitial fluid. In turn, convective fluxes of interstitial fluid increased the rate of β-amyloid clearance during sleep. Thus, the restorative function of sleep may be a consequence of the enhanced removal of potentially neurotoxic waste products that accumulate in the awake central nervous system.

Exactly, the flushing effect. Which you can also feel when you do some forms of meditation :)

I'm curious - do you have a physical sensation when this happens to you? Is there any evidence to support this claim? I ask because I often feel similar to brushing my teeth when I meditate, it's hard to explain though.

I can relate, but I interpret it as mental cleaning. Letting go of garbage thoughts etc, not literal toxins through the blood, but I assume it also helps this process, by relieving of stress. A body under stress works intentionally different, than a relaxed body. (Stress means some kind of threat, not the time to do cleaning)

Hm, there's that, sure. But I get it physically tho, too. I actually feel this: the pumping. It's only a certain type of focus tho. You may not yet have attained it, or perhaps not everyone is physically capable. But I'm happy to try to teach you to do it: reach out to me heh :)

Brushing your teeth? That's interesting heh! :)

On that: a buzzing sensation in your teeth? Yeah, I can relate. I think it's down to increased sensitivity to the nerves in your teeth that you normally don't pay attention to, but can be apparent when modifying your attention as in meditation. It could be something else, tho! :)

To your question on me: I feel this physically. This is not a 'claim', it's evidence: that I'm saying this to you.

You have no physical sensors that would allow you to "feel" events up there.

by what sense does one 'feel' tired?

Not literally, though 'feeling' does a lot of work in that sentence and rightly so. You don't exactly have a physical sensor to 'feel' sad either, which also happens up there mostly, but still people usually accept that we can 'feel' the experience of sadness.

Becoming aware of mental states influencing perception is how you register events up there (using meditation), which is what 'feeling' means in this context.

You can also feel things which don't exist, or not feel thing which exist, that's not really a basis for scientific discussions

Your eyes can't feel infrared yet they exist, and your eyes can be tricked into feeling movement when there is none (optical illusions)

I can find you people who feel the influence of Saturn on their mood...

I'm always wary of people using scientific lingo to "prove" their "feelings"; "flushing", "waves", "energy", "toxins", it's way too easy to fall into new age mumbo jumbo

It seems you don't trust your capacity for feeling. You need to develop that more, then maybe you will understand.

What you say is common among people who have not learned yet

Yes, I literally feel the flushing. And I also hear what you say about becoming aware of subtleness to expand your awareness.

This can also include physical sensations (not saying it’s the same thing as flushing, but), such as: feeling your heartbeat, feeling your blood pumping around. All of which I’m aware of, but I wasn’t before.

Thank you for your supportive comment :)

This seems like a pretty strong claim. What do you mean by physical sensors?

How does the body "up there" manage itself without being able to sense and interact with the physical (and chemical) world?

Sensors? Heh :) Well, however I am able to do this, I do it. And I feel it. And you don't know. So, your model must be wrong.

You’re probably just looking to feel better about how your sleep is not good, so you don’t want to see someone validating sleep effects are useful, or saying you could fix that by doing something else. I get you don’t want to believe this, but my direct experience trumps your belief.

But what you got to remember, is what you don’t have, is any ability at all to determine what physical senses or experiences or feelings or capabilities anyone else can have. You can only know yourself. And if you're coming from a limited point of view, it would be abusive to try to impose that to invalidate someone else, who’s coming from a broader perspective. Hahahaha! :)

That paper is referenced in the one linked. The authors are not unaware of it.

And?

Does it succesfully refute it?

Or is the new study just another study with bad methodology that wont be replicating?

Or maybe the first one is?

Individual studies aren't worth considering, especially after they just came out. Call me when they have settled about it, 10+ years from now.

The way they refute it is interesting.

> Those authors observed that fluorescent dyes injected into the cerebrospinal fluid (CSF) via the cisterna magna penetrated further into the cortex during sleep and anesthesia. They interpreted this as showing that molecular movement into the cortex must be faster during these states. However, the concentration of dye in any brain region will always be the difference between its rate of arrival and its rate of departure and so increased dye penetration in sleep and anesthesia can be equally well explained by a reduced rate of clearance rather than an increased rate of entry.

So the previous paper assumed that the presence of dye further into the brain meant more clearance, but these authors point out that the presence of more dye could mean less clearance (because if the fluid isn't being replaced as quickly the dye can simply diffuse further). The previous authors also injected dye into the CSF, which complicates matters as the CSF is moving both into and out of the brain all the time.

However:

> Our data in Figs. 2 and 3 show that, averaged across the brain, clearance is reduced by both sleep and anesthesia

... if you just focus on average dye concentration in the brain, and you inject the dye directly into the brain (the parenchyma) rather than into the CSF, the mean concentration is higher after a period of sleep than it is after a period of wakefulness. Which suggests less clearance, rather than more clearance, during sleep.

What are the practical implications anyway?

Sleep is good and lack of sleep is bad, I think that is a pretty established fact already.

And this is important basic research, but I do not see how it would influence me personally.

Why then does one feel refreshed after a nap?

I assert that dreams are a co-necessity for the effect. Sleep without sufficient dreams won't achieve it.

I wonder how sleeps affected our brain, and how there is a man who do not sleep for decades and does not lose energy.

*toxicants

I have anecdotal evidence from a long term study (~40 years) that suggests otherwise hahaha! :) tho I know some amount of sleep can reduced naturally using certain forms of seated meditation.

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