A different take on this: I am experiencing sleep apnea when I am awake, but only when I meditate (stress reduction strategy... it works!). I think a lot of people would consider stitching, knitting, computer games etc to be "meditative"... gets your brain to function in a different mode, very much like some stages of sleep. For me though, it does not happen if I meditate sitting up, only if I meditate laying on my back (which I stopped doing, for obvious reasons... how can you relax when you are afraid of chocking!!!). So I do believe it is very much related to sleep apnea.
So, are any of you knitting laying down on your backs???
Seriously though, I think “holding your breath” is very different from sleep apnea. I am sure a lot of people do it when concentrating on something else (have you ever taken an aerobic/ab class… can you remember the instructor telling you to not forget to breath???). I think even my dog stops breathing when he concentrates on trying to catch that squirrel!!! My personal opinion (no expert here!) is that it has little to do with sleep apnea, and I doubt you would “die” while knitting or playing a computer game!