Because the arousal system controls or influences sleep-wake states, alertness and attention, Nelson and the research team questioned whether people with near death experiences may already have an arousal system predisposed to allowing intrusion of REM sleep elements during the transition between wakefulness and sleep.
Sleep paralysis is a common form of REM intrusion, which can cause a condition of temporary paralysis along with visual or auditory hallucinations immediately after waking up or before falling asleep due to an ill-timed disconnection between the brain and the body. Although it was once considered very rare, about 25 percent of all people have probably experienced sleep paralysis sometime during their life.
During a medical crisis, Nelson said muscle paralysis combined with an out-of-body experience could show many of the same prominent features of a near death experience. Near death experiences are responses to a life-threatening crisis, and are characterized by a combination of disassociation from the physical body, euphoria and transcendental or mystical elements.
This investigation supports the notion of out-of-body experiences as an expression of arousal in near death experiences and sleep paralysis. Almost all of the near death subjects having sleep paralysis, 96 percent, also had an out-of-body experience either during sleep transition or near death.
"The strong association of sleep paralysis with out-of-body experiences in the near death experience subject is curious and unexplained," Nelson said. "However, persons with near death experiences appear to have an arousal system predisposed to both REM intrusion and out-of-body experiences."