I read some blog posts out there mentioning that one should get up early. Somewhere - unfortunately don't remember where - I read about the daily program of some blogger. Get up at 4 and go to sleep at midnight.
Well, after my son was born about a month ago, I experienced similar daily sleeping times. It can be compared to my experiences at military service. My interests after a while were reduced to eating and sleeping.
The effects are further head ache, concentration problems and so on. When walking to the gym it gets more and more difficult to perform as I performed months ago. Weights must be reduced and breaks have to be longer. I am awake longer to accomplish the things I wasn't able to finish before. Finally I saw that it is far from efficient running that way.
I try now to get to sleep whenever my son is also sleeping to get the hours required to ensure that I "function" well.
Getting enough sleep is a required precondition for efficient working and getting the output in an acceptable quality.
Related post: The value of rest and review.