1. Type 2 diabetes
2. Congestive Heart failure
3. Prostate enlargement
4. Irritable bladder
5. Urinary tract infections
In my case, I awaken 6-8 times a night even with successful treatment of OSA (my AHI=1.0 or less). I have no trouble falling asleep or going back to sleep. I am being treated for a mildly enlarged prostate. All other things on the list have been ruled out, except possible anxiety and depression. When I awaken, perhaps I am anxious that if I don't use the bathroom, I can't fall back to sleep. I try not to go, but can't sleep if I don't. My bladder can't be full, since volumes voided are so small even when I void frequently. I have currently asked for a trial of an antidepressant to see if that helps, although I don't feel depressed.
I have placed on Nortriptyline. If that doesn't work, we may trazadone.
The only reason I am posting my personal experience is that you can't always expect OSA treatment to correct nocturia, when you may have, as I do, multiple causes for awakenings. There are many causes for nocturia and you may have more than one reason for your problem.