Does the level of awareness of an awakened buddhist also stay the same event when he sleeps? But when an enlightened person lives he could be in the present all the time. But when you sleep your conscious/awareness may be different or just disappear. 

So does the level of awareness of an enlightened person also change or stay the same even when sleeping.
sleep is a state of body, not a state of mind. If you are asleep your body has shut down the 5 senses, but your mind can still be active (dreaming).


  "As for those delusion-born fevers — burned with which the householder or householder's son would sleep miserably — that delusion has been abandoned by the Tathagata, its root destroyed, made like a palmyra stump, deprived of the conditions of development, not destined for future arising. Therefore he sleeps in ease. - AN 3.34


If you are practicing mindfulness and meditation regularly you can actually stop nightmares from happening by this habit.