It's an unusual area of science, but after a patient described mysterious experiences and feelings during a close brush with death, Dr. Kevin Nelson knew he wanted to learn more.
"It was so vivid to him. I was struck by the intensity of the report he gave me," Nelson said of the patient's near-death experience, which occurred when Nelson was a medical intern.
Nelson, now a neurophysiologist at the University of Kentucky, published one of the few studies on the subject in today's issue of the journal Neurology. The study compares the sleep patterns of 55 people who have reported unusual sensations during a during near-death experience to 55 people who haven't.
For the study, near-death experience was defined as "a time during a life-threatening episode of danger such as a car accident or heart attack when a person experienced a variety of feelings, including a sense of being outside of one's physical body, unusual alertness, seeing an intense light, and a feeling of peace," according to a news release describing the study.
He and his team of researchers discovered that the near-death study group had a significantly higher rate (60 percent compared with 24 percent) of a sleep disorder known as rapid eye movement, or REM, intrusion.
This disorder causes one of the most active dream states of sleep -- REM -- to intrude into wakefulness, causing a person to sometimes wake up and feel paralyzed, experience leg muscle weakness or wake up to hear sounds other people didn't.
This may explain why some people have near-death experiences after undergoing a traumatic event that causes unconsciousness, Nelson said. When a person is under the threat, their fight-or-flight nervous system is evoked. But as they come out of unconsciousness, some mental wires may be crossed.
Nelson said it is important to understand that he wasn't trying to debunk any of the reasons why near-death experiences occur. He wanted to understand the how not the why, he said.
"This does not impact on the personal meaning of these experiences," he said.