I don't recall how long you need to sleep to go into REM (two hrs?). I would say if I stop breathing 150 times in an hr that I am not in REM for much at all. <vbg>
I'm surprized that I have lived as long as I have with the lack of sleep that I get! Miracle I don't screw up more stuff at work ...... LOL. Some how I manage.
I'm awake a lot longer than most people - so does that mean I get more done/accomplished in the course of a day?! Ummm..... probably not.
Regardless - when I use my CPAP, I do feel more rested.
May be that is what I am always grumpy?!