By Michael Smith,
MedPage Today Staff Writer
LEXINGTON, Ky, April 10 - So-called near-death experiences -- the widely reported sensations, in times of peril, of floating above the body, seeing a white light, and having a sensation of peace -- may be related to poorly regulated arousal systems in the brain, according to researchers here.
In a case-control study, people who reported near-death experiences were more likely than controls to also report elements of an aberration of the wake-sleep cycle known as REM intrusion, said neurologist Kevin Nelson, M.D., of the University of Kentucky.
If the normal boundaries between sleep and wakefulness are not clearly regulated, the rapid eye movement (REM) state of sleep can intrude into normal wakeful consciousness, Dr. Nelson and colleagues reported online today in the journal Neurology. This can have such consequences as waking up and feeling unable to move, having sudden muscle weakness in the legs, and hearing sounds just before falling asleep or just after waking up that other people can't hear.
"It's intuitive to most neurologists that the arousal system is going to be highly engaged in circumstances of near death," Dr. Nelson said in an interview. "And a key element of the arousal system is the REM system."
The possible link between REM intrusion and near-death experiences, Dr. Nelson said, was suggested by the similarity of some of the sensations, as well as by the observation that REM intrusion underlies other clinical conditions, such as narcolepsy.
For example, Dr. Nelson said that one of the most common manifestations of REM intrusion is visual hallucinations -- something that parallels the "white light" often reported in near-death experiences.
"I think that this (hypothesis) may explain some of the phenomena," he said.
Near-death experiences are measured using the 16-element Greyson near-death experience scale, which is broken into four categories - cognitive, affective, purportedly paranormal, and apparently transcendental -that includes such things as an altered sense of time, a feeling of peace, vivid senses, the sense of being out of the physical body, and a sense of deceased or religious spirits.
A person who experienced all of the elements of the scale would have a score of 32. To qualify as a near-death experience requires a minimum score of seven.
The researchers asked 446 North Americans who had reported a near-death experience to answer questions about the event. Sixty-four agreed and structured interviews were conducted with 55 consecutive volunteers.
To be eligible, the volunteers had to have had both an acute episode of danger and an experience that reached at least seven on the Greyson scale. Three volunteers were excluded because their Greyson scale rating was less than seven and six because their danger was not imminent.
Controls were age- and sex-matched staffers and contacts of the university's medical center, who had not had a near-death experience.
The study found:
Dr. Nelson and colleagues cautioned that the study was retrospective and based on questionnaires, but it presents what he called a "testable hypothesis" that could be examined in a range of clinical circumstances.
If the hypothesis is correct, he said, the phenomenon might be operative in common fainting; physicians should be aware that patients who faint may report similar sensations as patients have a near-death experience.
He noted that studies show about one in 10 patients who survive a cardiac arrest reports a near-death experience, but patients are often "hesitant to report to the physician these very unusual kinds of experiences," especially if the doctor gives the impression of being too busy to listen. Again, he said, doctors should be aware of the possibility.