Near death experiences appear to have a biological explanation, research suggests.
Dream sleep can intrude into normal wakeful consciousness
The US team said the same parts of the brain are activated when people dream as in near death experiences.
The study, in Neurology, compared 55 people who had had near death experiences and 55 who had not.
Those with near death experiences were more likely to have less clearly separated boundaries between sleeping and waking, the scientists found.
People who have had near death experiences commonly report being surrounded by a bright light or gazing down on themselves in an operating theatre.
Many of these sensations are also common to experiences of being in the dream state, or rapid eye movement (REM), stage of sleep, the researchers said.
Near death experiences were defined by the University of Kentucky researchers as a time during a life-threatening episode when a person undergoes an out-of-body experience, unusual alertness or sees an intense light or feels a great sense of peace.
They found 60% of those who reported such experiences said they had experienced the REM state of sleep during periods of wakefulness.
Only a quarter of those who had not had near death experiences said they had experienced this "REM intrusion".
Examples of this include waking up and feeling unable to move, having sudden muscle weakness in the legs and hearing sounds just before falling asleep or waking up that others do not hear, the team said.
Study author Professor Kevin Nelson of the University of Kentucky, Lexington, who led the study, said the findings suggests that REM state intrusion contributed to near death experiences.
He told the Daily Telegraph: "I see it as an activation of certain brain regions that are also active during the dream state.
"However, I hesitate to call it dreaming or dreaming while awake. This is the first testable hypothesis of a biological basis for these experiences."
"People who have near death experiences may have an arousal system that predisposes them to REM intrusion," he added.
However, he suggested the theory did not automatically rule out a spiritual dimension to near death experiences.
"We, as neurologists. address the how of these experiences coming about but not the why," he said.
Dr Neil Stanley, director of sleep research at Surrey University, said the theory was a very plausible one.
He said: "There are plenty of rational people who say that these things happen and the one part of us that's utterly fantastical is our dreams.
"Our dreams can appear incredibly real - after all they are our reality when they are happening.
"If you get that sort of reality playing through into your consciousness - it's a very convincing reason to believe such a thing is happening."