user157: Over the last few months I've started meditating late on a night (as well as my usual morning practice). I'm finding that I am sleeping less but not feeling tired because of it. Is there any information around about how mediation may or may not affect sleep patterns? 
For instance Dipa Ma, the Indian housewife and meditation teacher was up at 4.00 am every morning to meditate for a few hours presumably finding that perfectly OK. That said Margaret Thatcher only slept for 4 hours a night and I would hesitate to call her a Buddhist meditation master.

user295: More you meditate less sleep you need. The need for sleep is based on how energetic you are. Meditation stirs up more energy and you become energetic.

Similarly, when you go to bed at night, close your eyes and feel sensation anywhere within the body. If you fall asleep with this awareness, naturally as soon as you wake up in the morning, you will be aware of sensation. Perhaps you may not sleep soundly, or you may even remain fully awake throughout the night. This is wonderful, provided you stay lying in bed and maintain awareness and equanimity. The body will receive the rest it needs, and there is no greater rest for the mind than to remain aware and equanimous. However, if you start worrying that you are developing insomnia, then you will generate tensions, and will feel exhausted the next day. Nor should you forcefully try to stay awake, remaining in a seated posture all night; that would be going to an extreme. If sleep comes, very good; sleep. If sleep does not come, allow the body to rest by remaining in a recumbent position, and allow the mind to rest by remaining aware and equanimous.

...

At first it may seem a heavy burden to devote two hours a day to meditation, but you will soon find that much time will be saved that was wasted in the past. Firstly, you will need less time for sleep. Secondly, you will be able to complete your work more quickly, because your capacity for work will increase. When a problem arises you will remain balanced, and will be able immediately to find the correct solution. As you become established in the technique, you will find that having meditated in the morning, you are full of energy throughout the day, without any agitation.

Source: The Discourse Summaries

user-1: In Dvedhavitakka Sutta it is said that thinking tires the body. So I believe that meditation helps the body be more energetic by taking away some of the tiring thinking.
[...]

"And as I remained thus heedful, ardent, & resolute, thinking imbued with renunciation arose in me. I discerned that 'Thinking imbued with renunciation has arisen in me; and that leads neither to my own affliction, nor to the affliction of others, nor to the affliction of both. It fosters discernment, promotes lack of vexation, & leads to Unbinding. If I were to think & ponder in line with that even for a night... even for a day... even for a day & night, I do not envision any danger that would come from it, except that thinking & pondering a long time would tire the body. When the body is tired, the mind is disturbed; and a disturbed mind is far from concentration.' So I steadied my mind right within, settled, unified, & concentrated it. Why is that? So that my mind would not be disturbed. 

[...]

user-1: Meditation can definitely cause you to sleep less. When meditating one is naturally entering a calmer state of mind.
When doing Samatha meditation one is temporarily suspending the hindrances thereby limiting the effect of worries, excessive thinking, restlessness, cravings, aversions, anger etc. This naturally leads to a more simple and unified mind. Such a mind will affect the physical body and calm it down.
The human brain uses more energy than both arms and legs together on e.g. cognitive processes. All the stress from the hindrances will sooner or later manifest itself in the physical body as stress, i.e. an increased secretion of stress hormones such as cortisol and adrenalin. This will create a lot extra tension and load on the internal organs which in turn will increase the demand for energy.
The result of that is the need for more sleep.
Now if one removes the above things then one naturally needs less sleep.
If we take a look at Vipassana Meditation then here we are directly working with the hindrances, i.e. by weakening them to the point where they can be eradicated completely. In vipassana meditation we learn to see reality for what it is, meaning that the mind do not extrapolate on phenomena. The mind do no follow after phenomena thereby launching a process of ideation and planning on how to posess the object.
A non-meditator, i.e. the untrained mind will not have this ability to see clearly. The untrained mind will see an object for a brief moment whereafter it will launch the process of ideation, extrapolation, judging, imagining, liking, disliking etc. Imagine how much energy these cognitive processes demand.
If one trains in clear comprehension one gradually builds the ability to stop the mind from launching these cognitive processes by applying mindfulness to mental and physical phenomena as they arise and cease. With time and training the mind will become deeply rooted in the present. It will become calm, peaceful and equanimous no matter what arises.
A reduction in mental stress levels results in the physiological processes of secretion of stress hormones will be stopped and reversed resulting in a calmer body and a lot less load on internal organs. 
At night the body regrows tissue, builds muscle and bone and strengthens the immune system. When there is less load on the body then it also needs less time for restitution, i.e. less time to sleep.

user-1: The reason the body do not need as much sleep when one do a lot of meditation is because while we meditate, we are getting some rest that the body needs. Meditation increases the production of melatonin in our bodies. Melatonin is a hormone known for creating restful sleep.
This article might help. 

157: <p>Over the last few months I've started meditating late on a night (as well as my usual morning practice). I'm finding that I am sleeping less but not feeling tired because of it. Is there any information around about how mediation may or may not affect sleep patterns? </p>

<p>For instance <a href="http://en.wikipedia.org/wiki/Dipa_Ma" rel="nofollow">Dipa Ma</a>, the Indian housewife and meditation teacher was up at 4.00 am every morning to meditate for a few hours presumably finding that perfectly OK. That said <a href="http://en.wikipedia.org/wiki/Margaret_Thatcher" rel="nofollow">Margaret Thatcher</a> only slept for 4 hours a night and I would hesitate to call her a Buddhist meditation master.</p>
 295: <p>More you meditate less sleep you need. The need for sleep is based on how energetic you are. Meditation stirs up more energy and you become energetic.</p>

<blockquote>
  <p>Similarly, when you go to bed at night, close your eyes and feel sensation anywhere within the body. If you fall asleep with this awareness, naturally as soon as you wake up in the morning, you will be aware of sensation. Perhaps you may not sleep soundly, or you may even remain fully awake throughout the night. This is wonderful, provided you stay lying in bed and maintain awareness and equanimity. The body will receive the rest it needs, and there is no greater rest for the mind than to remain aware and equanimous. However, if you start worrying that you are developing insomnia, then you will generate tensions, and will feel exhausted the next day. Nor should you forcefully try to stay awake, remaining in a seated posture all night; that would be going to an extreme. If sleep comes, very good; sleep. If sleep does not come, allow the body to rest by remaining in a recumbent position, and allow the mind to rest by remaining aware and equanimous.</p>
</blockquote>

<p>...</p>

<blockquote>
  <p>At first it may seem a heavy burden to devote two hours a day to meditation, but you will soon find that much time will be saved that was wasted in the past. Firstly, you will need less time for sleep. Secondly, you will be able to complete your work more quickly, because your capacity for work will increase. When a problem arises you will remain balanced, and will be able immediately to find the correct solution. As you become established in the technique, you will find that having meditated in the morning, you are full of energy throughout the day, without any agitation.</p>
</blockquote>

<p>Source: <a href="http://www.vridhamma.org/The-Discourse-Summaries" rel="nofollow">The Discourse Summaries</a></p>
 -1: <p>In Dvedhavitakka Sutta it is said that thinking tires the body. So I believe that meditation helps the body be more energetic by taking away some of the tiring thinking.</p>

<p>[...]</p>

<blockquote>
  <p>"And as I remained thus heedful, ardent, &amp; resolute, thinking imbued with renunciation arose in me. I discerned that 'Thinking imbued with renunciation has arisen in me; and that leads neither to my own affliction, nor to the affliction of others, nor to the affliction of both. It fosters discernment, promotes lack of vexation, &amp; leads to Unbinding. If I were to think &amp; ponder in line with that even for a night... even for a day... even for a day &amp; night, I do not envision any danger that would come from it, <strong>except that thinking &amp; pondering a long time would tire the body. When the body is tired, the mind is disturbed; and a disturbed mind is far from concentration.' So I steadied my mind right within, settled, unified, &amp; concentrated it. Why is that? So that my mind would not be disturbed.</strong> </p>
</blockquote>

<p>[...]</p>
 -1: <p>Meditation can definitely cause you to sleep less. When meditating one is naturally entering a calmer state of mind.</p>

<p>When doing Samatha meditation one is temporarily suspending the hindrances thereby limiting the effect of <em>worries, excessive thinking, restlessness, cravings, aversions, anger etc.</em> This naturally leads to a more simple and unified mind. Such a mind will affect the physical body and calm it down.</p>

<p>The human brain uses more energy than both arms and legs together on e.g. cognitive processes. All the stress from the hindrances will sooner or later manifest itself in the physical body as stress, i.e. an increased secretion of stress hormones such as <em>cortisol and adrenalin</em>. This will create a lot extra tension and load on the internal organs which in turn will increase the demand for energy.</p>

<p>The result of that is the need for more sleep.</p>

<p>Now if one removes the above things then one naturally needs less sleep.</p>

<p>If we take a look at Vipassana Meditation then here we are directly working with the hindrances, i.e. by weakening them to the point where they can be eradicated completely. In vipassana meditation we learn to see reality for what it is, meaning that the mind do not extrapolate on phenomena. The mind do no follow after phenomena thereby launching a process of ideation and planning on how to posess the object.</p>

<p>A non-meditator, i.e. the untrained mind will not have this ability to see clearly. The untrained mind will see an object for a brief moment whereafter it will launch the process of ideation, extrapolation, judging, imagining, liking, disliking etc. Imagine how much energy these cognitive processes demand.</p>

<p>If one trains in clear comprehension one gradually builds the ability to stop the mind from launching these cognitive processes by applying mindfulness to mental and physical phenomena as they arise and cease. With time and training the mind will become deeply rooted in the present. It will become calm, peaceful and equanimous no matter what arises.</p>

<p>A reduction in mental stress levels results in the physiological processes of secretion of stress hormones will be stopped and reversed resulting in a calmer body and a lot less load on internal organs. </p>

<p>At night the body regrows tissue, builds muscle and bone and strengthens the immune system. When there is less load on the body then it also needs less time for restitution, i.e. less time to sleep.</p>
 -1: <p>The reason the body do not need as much sleep when one do a lot of meditation is because while we meditate, we are getting some rest that the body needs. Meditation increases the production of melatonin in our bodies. Melatonin is a hormone known for creating restful sleep.</p>

<p><a href="http://eocinstitute.org/meditation/require-less-sleep-with-meditation-460/" rel="nofollow">This article might help</a>. </p>
