Recently I saw this issue come up yet again when reading a survivor's account of dealing with cold weather. So I took a chance and emailed the renowned
Dr. Gordon Giesbrecht, asking him about his thoughts on "dying in your sleep from cold". I even sent him the link to this thread and asked if he would consider posting here. I can't think of a better expert to consult on this topic.
I highly recommend the 2nd edition of
Hypothermia, Frostbite, and Other Cold Injuries which was revised by Dr. Giesbrecht.
Check out Dr. Giesbrecht's
Cold Water Boot Camp, especially
their videos.