Hi there,
It took me a really long time to put two and two together as far as my open bite and my constant fatigue are concerned. I had braces for a little over a year when I was 14 and my bite was closed until about 6 months after I had my braces off. I later had braces AGAIN when I was 19, along with W-Wire expander which was VERY uncomfortable and gave me an awful lisp. It didn't seem to be expanding my palate or fix my bite, so I gave up on that at about month 6 and figured it wasn't THAT big a deal that I couldn't bit through things with my front teeth anymore. I'd already lived with it for 4 years.
As far as being tired, which I began struggling with at around 16, I think - I was originally diagnosed with Grave's Disease. I had a (very!) mildly overactive thyroid and was put on medication for that. It got my hormone levels in the right range, but didn't do a whole lot for my fatigue. I felt about the same as always.
Later I treated my anxiety and depression with SSRIs, which certainly helped my mood... but again, I was still tired all the time.
Finally, a couple years ago I came down with bronchitis and my breathing became very bad. I was put on prednisone (a steroid) for quite some time. I felt GREAT. Even though I was sick, my attention span was fantastic, my motivation was up, and I felt positive in a way I hadn't felt in years. It finally occurred to me that that was how I used to feel most of the time.
My GP happened to suffer from sleep apnea himself, so when we discussed all the possible reasons for my continued struggle and came to a dead end, he sent me for a sleep study.
It hadn't even OCCURRED to me I might have sleep apnea. I never realized I woke up in the night. I had some weird nighttime behaviors (acting out stress dreams, shouting what I was yelling in my dream) and was ALWAYS ready for a nap, but I just never became conscious enough in the night to realize how restless I was.
Anyway, when I started researching sleep apnea, I found out that people with open bites often have constricted airways. On top of that, my nose was very narrow and with a very slightly deviated septum. I hadn't realized until about four people asked me that I was a mouth breather. I kept saying no - but when I started paying attention, I realized it was actually pretty difficult for me to breathe full time through my nose.
Moving the jaw forward actually widened my nose a bit and now I can BREATHE. Besides the jaw surgery (upper 6mm and lower 11mm), my surgeon also did some septum work. It's taken me awhile post surgery to find a good circadian rhythm (a lot of disruptions at first with medication and discomfort), but even so I definitely already feel an improvement in my energy levels, concentration, and motivation.
Anyway, I'd definitely recommend doing a sleep study if you haven't already. If your surgeon knows you have sleeping difficulties, they may do the surgery somewhat differently than if it is just to fix an open bite.
Good luck with your surgery!