It’s believed we need sleep because of a waste product called adenosine builds up in our brains while we’re awake. When we’re unconscious the waste stops building up and the CSF in the brain gets rid of it. Adenosine is a CNS depressant and works on the same receptors as sleeping pills so wouldn’t it be like the idea of holding your breath until you die, you’d just involuntarily pass out (as if you’d been given anaesthesia) and the problem would solve itself? I’m imagining a CNS depressant would cause unconsciousness long before it got to lethal levels.
I think heart problems could actually make it possible to hold your breath until you die. You wouldn’t suffocate, but the stress on the heart would still kill you.
A drinker and a smoker? Probably stressed their heart too much.