Nocturnal polyuria

I haven't been using a CPAP quite as long as you have but I currently wake up once or twice a night where previously it seemed to be 3 to 4 times at night. I do take tamsulosin in the evening for BPH and have reduced the caffeine I drink during the day and limit the liquids after 6pm which seems to help. The National Association for Incontinence has some good information on treatment and management of nocturia which might be helpful - https://nafc.org/nocturia/.

There are several related discussions and comments from other members on nocturia that you might want to scan through to learn what has been shared - https://connect.mayoclinic.org/search/discussions/?search=nocturia.

It is very much an individual thing, and there may be a genetic component. Then again, maybe not; my father rises at least three times each night, and has done so for a couple of decades at least. He's 94. I am 72 and don't have to void at all. Not even once. And, to rub it in a wee bit, not even close. My bladder is never more than half full.

The pituitary gland secrets a hormone called antidiuretic hormone, or ADH. When we are in younger times, we produce more of it while we sleep for that very reason...to keep the kidneys from high throughput of water. As we age, most of us produce less and less ADH, and you are only too familiar with the rest of it. How I escaped that result is beyond me, and no, I don't gloat about it. I just count it as a blessing. Instead, I have atrial fibrillation and severe sleep apnea and cold sores now and then. Hey, nobody's perfect!

hmm, you are male and BPH is benign prostate hyperplasia ?
I had it in 2015 , then laser enaculation and all is well since then,
prostate-wise. So I'd recommend it.