I spent 4+ years not getting any REM sleep and my metabolism STILL suffers as a result - even 14 years after starting on CPAP and using it EVERY night since then.
It's too long to go into here - but I did a writeup years ago about my "journey", along with my wife's issues with PCOS (Polycystic Ovarian Syndrome).
http://weblog.mrbill.net/archives/2014/01/13/falling-in-love...
Do you snore (badly)? Do you find yourself tossing and turning a LOT at night? Do you wake up gasping or with a general sense of dread/fear? Are you super-tired during the day? Have you ever fallen asleep while typing, while at a stoplight in your car, etc? Talk to a doctor about having a sleep study done. It might save your life.