I too have sleep apnea diagnosed in about 2008 and have used C-PAP since. I think you mentioned that Sleep apnea may increase inflammation. If my body is any example, I'd say it must, but I can't prove it.
And as you said, heart health, brain and entire body due to oxygen deprivation. I just got diagnosed with PMR and confirmed by Ultrasound of shoulder 7/31/26 and started at 15mg Prednisone that day. It hasn't resolved my left shoulder arm/upper back girdle and the pain in that arm wakes me up every night. All the rest of my body, pain and symptoms have resolved except for this. We raised it to 20mg 8/5/26 but that hasn't worked, so we tried splitting it 15mg am, 5mg 1-2pm, but I couldn't sleep at all and after all these months without sleep, I can't tolerate that. It didn't help either. We'll try 25mg for 2 weeks and if that does resolve these last symptoms she wants to image my left shoulder to check for injury. I definitely do have old injuries on left side so they may interfere with the Prednisone in some way. Something else that's occurred to me is whether or not Lymph fluid may be blocked on my left side due to muscle spasm and old injuries. Just a thought.
I've been struggling with sleep since on 20mg so looked into melatonin but when searched melatonin with PMR and Prednisone it said melatonin can raise your glucose further than Prednisone already does. I'm 73 and don't want to take any chances with further blood sugar issues.
It recommended Magnesium Glycinate. I'm going to switch from Mag Citrate to Glycinate and clear with my Rheum. I'll start with about 200mg and go up to 320mg (I think 400mg is max). May you and everyone get better sleep and may we all be able to get off Prednisone as soon as possible without flares (or as little as possible). Blessings.