Unfortunately, there are a lot of surprising ways that you could actually pass away, consciously or not, this phenomenon could happen for a variety of reasons. Of course, passing away in your sleep is one of them, so the next time when you are tired and say “I would like to sleep for an eternity” or when you are sad and think “I wish to sleep and never wake up” just try to drive away this thought, because, well, your wish can come true.
In fact, there has always been an association between sleep and death, especially in ancient Greek mythology where Sleep was the twin brother of Death.