@Stache I don’t know the actual medical answer to your question, but I know that deep sleep is considered the most restorative, so I guess that means that stage is very important to be rested and heal the body? Again, I’m guessing.
It’s much easier to be woken during the first stages of sleep and even REM, it’s easier than during deep sleep. Deep sleep is the stage right before REM, REM is the dreaming stage.
I think it matters which stage you wake up in for whether you feel horrible and tired or not when you are first awoken. So, what I mean is if your alarm goes off when you are in deep sleep or REM I’m guessing that’s when we feel the worst, but I’m not really read up on it.
Keep in mind feeling ok when you wake isn’t the same as getting enough sleep in total.
Also, if you drink caffeine daily, if you are waking up as you withdraw off of caffeine you are likely to feel a little crappy in the morning even if you slept enough. You need your fix.
I did a sleep study several years ago, and when the doctor called to give me my results, I told him, “I think I spend longer than average for an adult in deep sleep.” He was surprised that I knew that, because it was true I’m in that stage longer than the average adult. Children spend longer in deep sleep than adults, which is partly why children sleep so soundly. Most children can sleep through a lot of activity and noise going on around them.
I didn’t really answer your question, because I don’t know for sure the answer, but I’m just trying to say I think all the stages are very important, but completing deep sleep is probably the most important to get the benefits of sleeping.