People who say they've had a near-death experience -- which includes feeling outside of one's body, and an accompanying sense of peace -- often have different sleep-wake control systems than other people, U.S. researchers report.

The finding could help explain this experience in certain people, concludes a U.S. study in the April 11 issue of the journal Neurology.

Researchers compared 55 people who'd had a near-death experience to 55 people of the same age and gender who hadn't had this kind of phenomenon. For this study, a near-death experience was defined as a life-threatening event (such as a heart attack or traffic crash) when a person felt a number of sensations, including a sense of being outside their physical body, unusual alertness, seeing an intense light, and having a feeling of peace.

People with near-death experiences were more likely to have a sleep-wake system where the boundaries between sleep and wakefulness were not as clearly regulated as normal and the REM (rapid eye movement) state of sleep can intrude into normal wakeful consciousness, the study said.

Examples of REM state intrusion include: waking up and having the feeling of being unable to move; sudden muscle weakness in the legs; and hearing sounds just before falling asleep or just after waking up that other people can't hear.

Sixty percent of the people in this study who had near a near-death experience reported having REM intrusion, compared to 24 percent of the people who didn't have a near-death experience.

"These findings suggest that REM state intrusion contributes to near-death experiences. People who have near-death experiences may have an arousal system that predisposes them to REM intrusion," study lead author Dr. Kevin R. Nelson of the University of Kentucky in Louisville, said in a prepared statement.