Can meditation cause you to sleep less? 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.
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.