
Why We Sleep - blatherard
http://www.newyorker.com/science/maria-konnikova/why-we-sleep
======
septerr
Tldr:

When we sleep, our brains process the events of the day and pick out things to
stow away in our long term memory.

Maybe as a side-effect of this processing, they also aid problem solving -
after a good night's sleep, you are able to find solutions to the previous
day's problems faster (than you would, if you hadn't had the sleep).

As we sleep, our brains clear away toxins that accumulate during our awake
time. These toxins may be culprits behind neuro degenerative diseases.

There seems to be a correlation between sleep deprivation and cardiovascular
diseases.

~~~
jacobolus
Sleep also somehow helps the immune system do its thing properly. After a
night without sleep or a few days with insufficient sleep, the immune system
is partly compromised. As one example, multiple people I know with chronic
virus-caused skin conditions (like warts, herpes, ...) have symptoms when they
don’t get sufficient sleep. I know a couple people whose arthritis kicks into
high gear after insufficient sleep.

Sleep also definitely has a large effect on mood, I assume at least partly
through the mix of stress hormones produced; many people I have known closely
become extremely emotional and irritable when they haven’t had enough sleep.
Others become emotionally detached/withdrawn (at least, by outward
appearances).

~~~
rotten
I've also read that sleep can help with weight loss - but maybe that is a
stress related side-effect.

~~~
pm
I think it's more that cortisol (stress hormone) inhibits weight loss, and its
at higher levels when you don't get enough sleep.

------
wyager
It is, I think, often more enlightening to ask the question "why do we
awaken"?

I wonder if, a long time ago, some animal evolved the ability to enter brief
periods of elevated activity. This was obviously highly advantageous for e.g.
escaping predators, so over time this animal evolved to sustain this temporary
boost for longer periods. Today, animals can sustain this boosted state for
the majority of their lifetime. It is merely a matter of perspective that
leads us to consider wakefulness to be "normal" and sleep to be something out
of the ordinary.

~~~
jacquesm
You already answered the question: if you keep on sleeping you're vulnerable
and being vulnerable over a longer period of time equates to certain death. So
we awaken to stay alive when the cover of night disappears.

------
guelo
I hate it when I solve programming problems while sleeping. It makes me feel
like I'm working for free on my time off. They're only supposed to be renting
my brain for part of the day.

~~~
dsp1234
I hate it when I code the solution when I'm sleeping, then I wake up and am
forced to code it again for real. It's like the ultimate failure to Ctrl+S

------
netman21
I have an alternative answer to that question. Mammals evolved to sleep
because those young that gave their parents a rest survived childhood. Seems
obvious to any parent. :-) Imagine a puppy that never stopped. Its mother
would abandon it.

~~~
carsongross
Cute, but just turn the darwinian crank: the mother that didn't abandon it
would then have super-puppy offspring that would be able to secure far more
resources for themselves and their offspring.

The obvious advantages of not sleeping indicates to me that there is a deep
connection between sleep and our waking performance. If there weren't why the
hell would it have persisted across so many creatures for so long.

I _am_ confused by the fact that human young keep parents awake so much: it
seems like a delicate time to be introducing poor cognitive performance into
the mix.

But then a lot of things confuse me when I apply straight forward darwinian
thinking.

~~~
zyrthofar
I like to think that we evolved sleep because it's better, in the wild, to be
still and silent in the dark, than move around and make noise.

Since we can barely see in the dark and can't do anything anyway, wouldn't it
be preferable to minimize the time spent defenseless against predators with
better night vision? Staying still seems like a good strategy a lot of times,
when most animal visions, night vision or not, is based on movement.

It doesn't answer, though, why the top of the food chain need to sleep too.

~~~
ricree
It also doesn't explain why the effects of sleep are so strong, when an
instinct for watchful stillness would have been every bit as effective for
that purpose.

------
vernon99
There's a pretty convincing theory that says that while we sleep, brain is
processing signals from our internal organs instead of processing the sensory
input. Experimentors were triggering impulses in monkey stomach and seeing
them activate some areas of the brain that are normally used in the cognitive
process. That way brain inspects the organism and balances it's functions. One
of the side effects of this theory is that our dreams are just an
interpretation of these signals. Like your liver signals trigger some areas of
the brain and that produces the weird imaginery we call dreams. Can't find the
link to that paper right away.

~~~
vernon99
Found some publications, the theory is called The Visceral Theory of Sleep,
spearheaded by Ivan Pigorev.

Intro:
[http://www.researchgate.net/publication/271920141_The_Viscer...](http://www.researchgate.net/publication/271920141_The_Visceral_Theory_of_Sleep)

Cortical visual areas process intestinal information during slow-wave sleep:
[http://onlinelibrary.wiley.com/doi/10.1111/nmo.12052/abstrac...](http://onlinelibrary.wiley.com/doi/10.1111/nmo.12052/abstract)

------
stuartd
This is where f.lux - [https://justgetflux.com](https://justgetflux.com) \- is
so great. After sunset in your location it gradually bleeds blue light from
your display: also at work I use it to just orange-ify the display a bit at a
constant rate - because work is lit by fluorescents - and on a bright monitor
it noticeably reduces eyestrain.

------
ommunist
Why would anyone want to "be productive" if he or she can just ... hm, sleep!

~~~
venomsnake
Story of my college years ...

