The other night, I had a dark dream in which a brittle, slender woman with long silvery tangled hair and a gown that looked like torn wispy seaweed like tatters, climbed upon my chest, over my body and I woke up thrashing to get her off. I gasped for air. Allergies had me completely congested. I rolled onto my side, but that unbelievably real image of the wizened woman plopping down on my chest sent a shiver through me. It was so real!
Sleep paralysis combined with sleep apnea (breathing pauses) combine to make a sense of something smothering one, sitting upon their chest, sucking out their breath. Lots of cultures didn't understand the shift between sleep cycles when paralysis is important during the dream state for the body to not act out dreams. Upon occasion, the body is still in paralysis while the mind is coming awake and hallucinations combine with inability to move to create everything from alien abduction, incubus, old hag syndrome, and many other scenarios to the troubled sleeper.
Lots of cultures have names for the sensation of something sitting upon one's chest in their sleep.
Stephen King's "Cat's Eye" was actually a freaking creepy movie. This little troll thing in a little girl's room (Drew Barrymore) sucks the breath from babies like the old legend. My son saw this as a little kid and was probably never the same since.
The Germans have a creature named "Alp" An alp is typically male...Its victims are often females, whom it attacks during the night, controlling their dreams and creating horrible nightmares (hence the german word Albtraum ("elf dream"), meaning a nightmare). An alp attack is called an Albdruck, or often Albdrücke, which means "elf pressure". Alpdruck is when an alp sits astride a sleeper's chest and becomes heavier until the crushing weight awakens the terrified and breathless dreamer. The victim awakes unable to move under the alp's weight. This may have been an early explanation for sleep apnea and sleep paralysis, as well as night terrors. It may also include lucid dreams. Alps may also enter the body by becoming a fine mist or a snake and entering through the nostrils and mouth, where it can administer nightmares from the inside, similar to a spirit possession. It also uses its long tongue in a similar fashion, for it is suggested that the alp "feeds" on dreams. When an alp attack is sexual in nature, it is said to be extremely unpleasant. An alp will however rarely force itself on a victim in this way, and sexual attacks by the alp are rare. An alp will repeat these sessions until it is repelled sufficiently, for it is quite persistent and determined once it selects its victim. In folk tales they have been reported to travel great distances to and from their favorite victim.
In Swedish folklore, sleep paralysis is caused by a Mare, a supernatural creature related to the werewolf. The Mare is a damned woman, who is cursed and her body is carried mysteriously during sleep and without her noticing. In this state, she visits villagers to sit on their rib cages while they are asleep, causing them to experience nightmares. An upcoming Swedish film, Marianne, examines the folklore surrounding sleep paralysis.
Every single culture has a story that explains this scenario. We often refer to the Old Hag which is the concept of a harbinger of something bad about to occur.
No matter how you add it up or explain it, the combination of sleep paralysis with sleep apnea, sometimes caused by being overweight, having a crowded throat (large uvula, thick throat tissues) or plain old head colds can create a suffocating feeling that is quite horrifying.
I'll take nightmares over that any time!