Violent Sleepwalkers Can Kill When Interrupted

About 2 percent of children, mostly boys, go on to be adult sleepwalkers, walking around, doing chores, eating and even climbing out windows and urinating in odd places.

Most Sleepwalkers Don't Kill

Most sleepwalkers don't kill people. Sleepwalking, or somnambulism, can involve getting dressed, strolling around the house or doing rote tasks.

Though the sleepwalker remembers nothing, the partner often reports strange behaviors.

Daniel Houghton, a 28-year-old teacher from Montpelier, Vt., jumped up one night, insisting to his girlfriend that he had a relationship with Osama Bin Laden.

"I think it was near the election debates," said Houghton. "McCain had just called Obama, 'Osama,' by accident during one of the debates. Apparently I was digging around the sheets for Osama Bin Laden's business card. In my dream it had fallen out of my pocket."

He had no memory of the nocturnal event. "Maybe she dreamed the whole thing," Houghton said.

But others can be a danger to themselves or others, driving cars, having sex with strangers and even killing.

In 2007, Nick Walker, 26-year-old British Air Force mechanic whose military nickname was "night walker," for his sleepwalking habits, was found not guilty of raping a 15-year-old during one horrific sleepwalking bout.

Surprisingly most violent sleepwalking occurs in the earliest part of the sleep cycle, during deep sleep, before REM (rapid eye movement) and dreams occur.

In another rare condition mostly seen in the elderly, REM behavior disorder, sleepers can react in direct response to a dream and hurt their bedmates.

Some researchers say it is an early precursor to Parkinson's disease.

"One case I had would sit up in bed abruptly, telling his wife he thought there was an anaconda in his bed," said Cartwright. "He told her, 'I'll grab the head, you grab the tail.' He thought he was protecting her."

In both REM and non-REM sleepwalking, eyes are wide open and sleepers are difficult to wake.

Usually, a sleepwalking session ends abruptly, leaving the person confused and disoriented upon waking, with no memory of the event.

Researchers say there is a genetic basis to sleepwalking -- children whose parents are sleepwalkers are two to three times more likely to go on to exhibit the same behavior.

The "architecture" of sleep looks like a skyline, according to Cartwright. As the brain begins to shut down all visual and audio input, the muscles relax and breathing is progressively slower and deeper.

In about 20 minutes the body is in deep sleep with the highest amplitude and slowest brain waves. It is during this time that walking and talking are most likely to occur. In children, those delta waves are accompanied by growth hormone.

"You are really out of it," said Cartwright.

But gradually, the deep cycle decreases and the waves have less amplitude, and after 30 minutes, the sleeper moves into the REM or rapid eye movement phase.

REM is characterized by a sudden and dramatic loss of muscle tone where the person is essentially paralyzed, except for the eyes, which dart like "ping-pong balls," breathing, and in men, erections.

It is also associated with dreaming and the blood pressure and breathing can be erratic.

Throughout the night, the brain moves between those two phases in 90-minute cycles, with deep sleep becoming shorter and REM periods longer.

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