<p>As mentioned in one of the TED talks by Russell Foster, we need sleep not only for resting or cleaning up, but also for developing memories. </p>

<p>In addition, a good sleep has also requirements (mostly environmental); e.g. no-light, no-noise room etc.</p>

<p>Here is the talk: <a href="http://www.ted.com/talks/russell_foster_why_do_we_sleep.html" rel="nofollow">http://www.ted.com/talks/russell_foster_why_do_we_sleep.html</a></p>

CC BY-SA 3.0
2013-12-28T11:27:37.013Z
2013-12-28T11:27:37.013Z
israkir
<p>Here's why people need to sleep:</p>

<p>The brain does its "cleaning up" during sleep. As cells in the nervous system are active, waste products are produced. In the rest of the body, waste removal is carried out by the lymphatic system, but this system does not extend to the brain. Instead, cerebrospinal fluid (CSF) must be pumped through the brain tissue in order to flush waste back into the circulatory system where it can be excreted by the liver. Pumping CSF seems to require a great deal of energy, and researchers speculate that this energy expenditure is incompatible with the intense metabolic demands of brain cells during wakefulness. Also, cells in the brain shrink considerably during sleep, resulting in a 60% increase in interstitial space which allows CSF to wash more freely through the brain tissue. The consequence is significantly faster clearance of neurotoxic waste (e.g., β-amyloid). </p>

<ol>
<li><a href="http://www.sciencemag.org/content/342/6156/373">http://www.sciencemag.org/content/342/6156/373</a></li>
<li><a href="http://stm.sciencemag.org/content/4/147/147ra111">http://stm.sciencemag.org/content/4/147/147ra111</a></li>
</ol>

CC BY-SA 3.0
2014-04-17T14:02:37.910Z
The "cleaning" hypothesis is just one, and it's a rather new one.  The debate about the function of sleep has been going on for a long time, and the community has not settled on maintenance cleaning being the answer.  There are also rest hypotheses (that neural cells need rest, but can't rest individually because they're coupled to other neurons, so they have to rest in large groups, requiring sleep) and there's also a hypothesis that sleep serves a memory and learning function (consolidation processes between hippocampus and cortex)
Keegan Keplinger
CC BY-SA 3.0
2013-12-24T23:08:59.580Z
Could you summarize the information in the papers within your answer, please?
Chuck Sherrington
CC BY-SA 3.0
2013-12-24T18:41:19.950Z
2013-12-24T23:57:34.730Z
2013-12-24T23:57:34.730Z
Doug
<p>I haven't slept for a day, but feel fine. It is sometimes assumed that one needs 8 hours of sleep each night, but I think this is sometimes not true. </p>

<p>Is it okay to get no sleep one night and then 8-9 hours sleep the next night, as long as it only happens occasionally (e.g., once a month)?</p>

CC BY-SA 3.0
2014-11-27T19:53:57.240Z
I recently saw an article in (I think) scientific American where they told about this guy who wanted to find out if our bodies' natural sleep cycle was due to day/night or other factors. He went and lived in a cave with no way to tell if it was night or day and apparently after a while he naturally started staying up for two days and sleeping for one. They figured this out because he was keeping track of what day he THOUGHT it was, based upon when he slept, and missed the mark on the appointed day that he was supposed leave by something like a month.
Ron Kyle
CC BY-SA 3.0
2013-12-20T08:16:02.563Z
I'd say you can manage with 4 hours per day, but then you would sleep a bit more during the weekend. If you're interested in the topic you could try searching for relevant books about sleep deprivation on http://www.goodreads.com/ - I'm sure there's something for everyone :)
SkyHiRider
CC BY-SA 3.0
2013-12-26T15:21:39.967Z
Related: http://cogsci.stackexchange.com/questions/868/can-you-catch-up-on-lost-sleep?rq=1
Steven Jeuris
<sleep><health-psychology>
Do you need sleep every night?
Jossie
# Do you need sleep every night?

(Asked by: username_0 on 2013-12-19)

I haven't slept for a day, but feel fine. It is sometimes assumed that one needs 8 hours of sleep each night, but I think this is sometimes not true.

Is it okay to get no sleep one night and then 8-9 hours sleep the next night, as long as it only happens occasionally (e.g., once a month)?

**Tags:** sleep, health-psychology

> **Comments:**
> **username_2**: I'd say you can manage with 4 hours per day, but then you would sleep a bit more during the weekend. If you're interested in the topic you could try searching for relevant books about sleep deprivation on http://www.goodreads.com/ - I'm sure there's something for everyone :)  
> **username_3**: Related: http://cogsci.stackexchange.com/questions/868/can-you-catch-up-on-lost-sleep?rq=1  
> **username_1**: I recently saw an article in (I think) scientific American where they told about this guy who wanted to find out if our bodies' natural sleep cycle was due to day/night or other factors. He went and lived in a cave with no way to tell if it was night or day and apparently after a while he naturally started staying up for two days and sleeping for one. They figured this out because he was keeping track of what day he THOUGHT it was, based upon when he slept, and missed the mark on the appointed day that he was supposed leave by something like a month.  

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## 2 answers

### Answer by username_5 on 2013-12-24. Score: 5 | Accepted answer

Here's why people need to sleep:

The brain does its "cleaning up" during sleep. As cells in the nervous system are active, waste products are produced. In the rest of the body, waste removal is carried out by the lymphatic system, but this system does not extend to the brain. Instead, cerebrospinal fluid (CSF) must be pumped through the brain tissue in order to flush waste back into the circulatory system where it can be excreted by the liver. Pumping CSF seems to require a great deal of energy, and researchers speculate that this energy expenditure is incompatible with the intense metabolic demands of brain cells during wakefulness. Also, cells in the brain shrink considerably during sleep, resulting in a 60% increase in interstitial space which allows CSF to wash more freely through the brain tissue. The consequence is significantly faster clearance of neurotoxic waste (e.g., β-amyloid).

1. <http://www.sciencemag.org/content/342/6156/373>
2. <http://stm.sciencemag.org/content/4/147/147ra111>

> **Comments:**
> **username_7**: Could you summarize the information in the papers within your answer, please?  
> **username_6**: The "cleaning" hypothesis is just one, and it's a rather new one.  The debate about the function of sleep has been going on for a long time, and the community has not settled on maintenance cleaning being the answer.  There are also rest hypotheses (that neural cells need rest, but can't rest individually because they're coupled to other neurons, so they have to rest in large groups, requiring sleep) and there's also a hypothesis that sleep serves a memory and learning function (consolidation processes between hippocampus and cortex)  

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### Answer by username_4 on 2013-12-28. Score: 0

As mentioned in one of the TED talks by Russell Foster, we need sleep not only for resting or cleaning up, but also for developing memories.

In addition, a good sleep has also requirements (mostly environmental); e.g. no-light, no-noise room etc.

Here is the talk: <http://www.ted.com/talks/russell_foster_why_do_we_sleep.html>


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