Over diagnosed. The doctor I saw at this sleep clinic was trying to tell me I had it even before I did a sleep study. I walked out and never went back.
Recently I found out from an osteopath that I had issues with my sternum (three bones doing all different things), due to either a bicycle accident as a child or adult, a car crash or a judo injury, which may have explained why I was having breathing issues. My collarbone was even jammed into my sternum, which was against an artery that goes up into my neck. My GP diagnosed me with mild asthma as a teen. I am already breathing better thanks to the osteopath.
Lesson here: everyone try to justify their profession. If your intuition tells you something isn't right with what you are being told, do some more investigation.