DAVID GREENE, HOST:
It's MORNING EDITION from NPR News. Good morning. I'm David Greene.
STEVE INSKEEP, HOST:
And I'm Steve Inskeep.
Today in Your Health, we have two perspectives on sleep. Disrupted sleep can cause memory problems later in life, as we'll hear in a moment.
GREENE: First, let's examine a common disruption - sleepwalking. Four percent of adults reported regular sleepwalking in a recent study. And it's even more common in children.
INSKEEP: It remains largely a scientific mystery, though researchers have detected some clues in the brains of sleepwalkers, like a teenager who spoke with Michelle Trudeau.
MIRANDA KELLY: The first time I really knew I was sleepwalking I was about 7 - 6 or 7.
MICHELLE TRUDEAU, BYLINE: Miranda Kelly is now 14, and every few months in the middle of the night she gets out of bed and wanders.
M. KELLY: I wake up in weird places. I have once woken up in the kitchen randomly, the floor of the bathroom, wrapped in my sheet.
DR. ALON AVIDAN: We do not understand the reason why people sleepwalk.
TRUDEAU: That's Alon Avidan, a neurologist at UCLA who studies sleepwalkers. Sleepwalking, he says, is basically the brain's inability to fully wake up.
AVIDAN: When you place electrodes on the sleeping brain, what you will see is a person going into slow wave sleep. The brain waves will be very slow.
TRUDEAU: It's called non-REM sleep or non-dreaming sleep. It's the very first stage of sleep and sleepwalking most typically occurs within this stage, during the first hour or two of falling asleep.
AVIDAN: As they experience the sleepwalking, you'll start seeing the brain partially awakened while the patient is still asleep.
TRUDEAU: The brain is caught in this twilight zone, partially asleep, partially awake.
M. KELLY: I usually don't realize when I do it. Like every couple of months I'll wake up in an odd place and realize, oh, I slept walked.
RUSSELL ROSENBERG: That's a key feature of it.
TRUDEAU: Sleep researcher Russell Rosenberg, chairman of the National Sleep Foundation.
ROSENBERG: The key component of sleepwalking is there's little or no memory for the episode whatsoever.
TRUDEAU: The typical sleepwalker, Rosenberg says, isn't dreaming, isn't acting out their dreams, but rather while in the deepest stage of sleep doesn't remember having wandered around or behaved oddly. Some research suggests that the sleepwalker's frontal cortex - the brain's center for decision-making, judgment, in addition to short-term memory - is not fully online during sleepwalking. This might explain some of Miranda's unusual behaviors and that she can't remember them.
M. KELLY: I have apparently come downstairs in the middle of the night, had Oreos and dunked them in milk, washed out my glass, and then just like fallen asleep in random places. Like, I have never known that I have done that.
TRUDEAU: Ten to 20 percent of children occasionally sleepwalk, but Rosenberg adds parents shouldn't worry.
ROSENBERG: It's a perfectly normal developmental phenomenon in which a child's brain is not fully developed or is immature, and the ability to arouse or awaken completely has not occurred just yet.
TRUDEAU: But as their brains mature, most kids will grow out of sleepwalking. For some, though, sleepwalking continues into adulthood. Like Miranda Kelly's dad.
STEVE KELLY: I'm Steve Kelly. I am 52.
TRUDEAU: Researchers say there's a strong genetic component driving sleepwalking. If one parent sleepwalks, the child has a 45 percent increased risk of being a sleepwalker, too.
And there are environmental triggers, such as not getting enough sleep or drinking too much alcohol or sleep apnea. One of the most common triggers is what usually precipitates Steve Kelly's sleepwalking - stress.
S. KELLY: When I was going to college for my master's degree, every semester around exams, I would start sleepwalking again.
TRUDEAU: Probably because stress causes you to lose sleep and sleep debt is a powerful trigger. But, unlike Shakespeare's Lady Macbeth - who would sleepwalk from guilt and madness - sleepwalkers do not typically sleepwalk because of psychological problems. Sometimes, however, the medicines prescribed for anxiety or depression, or even for sleep itself, such as Ambien, can trigger a sleepwalking episode.
And advice to a spouse or parent: the best thing you can do for a sleepwalker is quietly, gently guide them back to bed and keep them safe.
For NPR News, I'm Michelle Trudeau.