I have sleep apnea and sometimes don't get into the REM stage of sleep, where is where you get your rest... I usually wake up every 1 1/2 - 3 hours, so I take cat naps to try to get a little rest at a time... Sometimes I can sleep through the night when I'm wore-out tired....
Good friend of mine has it. We slept in the same room after a boxing event last year. Or he slept, rather. Me, not so much ... Got up at seven to pick up the car then woke him up and went home.
He's got this mask, though, that gives much relief. Some kind of pump that improves his breathing. He says it's given his life new meaning. Not sleeping ruins everything.