If this were normal for me, I wouldn't be too worried. I don't really like to sleep that much, and I've always envied D&D elves for their ability to trance. But I'm worried because less REM sleep means impaired higher cognitive functions and less concentration, and that leads to mistakes at work.
ehm... no. there are a lot of studies which say that 6 hours of sleep is enough. going over 9 hours can actually be bad for you. so don't worry.
Ignore the above.
Studies Zug may be talking about is the one that noticed people with depression and sickness tend to sleep more. Not understanding the difference between a symptom and a cause the ruled inconclusively on illogical fallacies to create one of the biggest lies being told (without citation) around the Internet. Hilariously it really makes fun of the several other studies that state kids need to sleep longer than adults as if to say kids should die.
Sleep requirements are based on the individual them selves. The duration of sleep doesn't matter number wise. If you are awake and refreshed for the day then currently that duration is what you need, but it could very well change in the next 24 hours. This is my opinion though, if you want a citation have literately the first hit on google for how long should I sleep?, and even it deputes the >9 YOU DIE lie.
I was, incidentally, at the doctor today. He mentioned that for someone with my lifestyle, 7-8 hours is probably a good bet; although 6 hours wouldn't exactly kill me. I should be okay, though.
Like I said, it's more because I don't know what's causing it and the fact it's not a normal thing for me that I'm worried. Not knowing can cause anxiety, and that very anxiety can alter my metabolism further, so it becomes a vicious cycle. My body feels perfectly fine for the most part - my heartrate is monitored often, as I exercise frequently -, it's just that if this is supposed to be the result of something I'm doing right, I'd like to know WHAT I'm doing right so I can keep doing it.
EDIT: And yes, I realize how weird it seems to complain about feeling better than normal!