I don't think the apple watch is as accurate as they claim, and it seems to need many nights of data to make a sleep apnea decision, so in that respect it is vastly inferior to polysomnography. But hey, if it helps more people seek a proper diagnosis, then I'm all for it. Sleep apnea sucks. It seriously ruins lives.

Also: SpO2 is less useful here than you might think. Most at-home sensors are pretty unreliable, and it's possible to have sleep disordered breathing without having significant desaturation.