Wake up, folks: There is no health risk in rousing a sleepwalker from their somnambulistic stroll. Well, no risk to them, anyway. You, on the other hand, might suffer a swift, roundhouse kick to the dome.

Long-repeated medical myths have held that if you forcibly snap a sleepwalker back to a wakeful state it will A) induce a state of shock or possibly even insanity, B) give them “lockjaw,” and, C), our personal favorite, cause their soul to become trapped outside their body. The truth matters now more than ever: On Monday, the Stanford University School of Medicine released new research estimating that 8.5 million U.S. adults (3.6 percent of the grownup population) went sleepwalking during the past year -- a far higher rate of nocturnal wanderers than previously thought by doctors. 

“It’s not dangerous for the sleepwalker to wake him up,” said Dr. Mark R. Pressman, a psychologist and sleep specialist at Lankenau Hospital in Wynnewood, Pa. “You’re not going to do them any harm.”

But there are two potential pitfalls in attempting to yank them back to the conscious world. First, sleepwalkers take their short journeys with eyes open yet without turning on a key part of their brain -- the frontal lobe, a portion that controls social interaction. They are momentarily trapped in an altered, gray state that falls between alertness and full sleep, making them quite difficult to bring back to the real world, Pressman said.

“You just can’t talk to them and say ‘Hey!” and have them wake up,” Pressman said. “I’m not even sure where that myth began that you shouldn’t wake them. But the more you dig back (to try research that legend), the more you’ll find that sleepwalking once was thought to be mixed in with spirits and demonic possessions.”

Most sleepwalking episodes last only seconds or a few minutes, ending with the person either sitting or lying on the floor and returning sleep or eventually trudging back to bed.

“It’s very likely to go away on its own while the family is watching,” Pressman said.

You can try to verbally redirect a sleepwalker -- especially a child -- by standing a short distance away and speaking to them in short, easy commands: “Stop, turn around, go back to bed.” But don’t expect them to answer or even to recognize you, Pressman said. Those particular neurons are still snoozing. “Hopefully they turn around and go the other way.

“There’s really no reason to dive in and stop it unless the sleepwalker is about to climb out a window or fall down some stairs. If that’s the case, the family member doesn’t really have much choice,” he added.

If you do approach a sleepwalker -- especially if you physically block or grab one -- they may flash some "defensive aggressiveness,” Pressman said. “This is a very primitive response to what they see as a potential attacker. They may become violent.

“The first thing, obviously, is you have to protect them anyway you can. That’s the bottom line: safety. So you may have to be prepared to take a punch or kick.”

Just don’t expect your zombified loved one or housemate to offer an apology. 

Related:

• Sleepwalking more rampant than thought, study shows
• Suicide while sleepwalking is a real nightmare
• Why do our eyelids get heavy when we're sleepy?

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This, finally, may explain our cultural obsession with zombies: Long after dark, millions of Americans basically become one.

Without warning, they suddenly rise from their silent, supine states then roam aimlessly, eyes open and mouths sputtering gibberish.

About 8.5 million U.S. adults -- or 3.6 percent of the grownup population -- have taken at least one sleepwalking jaunt during the past year, according to research released today by the Stanford University School of Medicine. That figure, calculated via a survey of nearly 20,000 people, means there are far more nocturnal wanderers than scientists previously suspected.

“It’s something, we were thinking, that was not frequent among the general population. And here, big surprise, it is,” said Dr. Maurice Ohayon, professor of psychiatry and behavioral sciences at Stanford and lead author of the paper. A previous report done a decade ago in European adults showed that 2 percent of that population were sleepwalkers. “It’s astonishing.”

The finding offers American doctors their first, solid sleepwalking benchmark, Ohayon said. Earlier speculation on how often the phenomenon occurred were based on anecdotal clinical reports as well as court cases and media tales of people who had gone sleep-driving, sleep-shopping or sleep-eating. Typically, those more sensational examples were linked to Ambien use.

But Ohayon and his colleagues found no significant link between prescription sleeping pills and increased sleepwalking. What they did discover: Folks who take certain anti-depressants (selective serotonin reuptake inhibitors, or SSRIs) are three times more likely to also take a snoozy stroll than the general population, and people who swallow over-the-counter sleeping pills have a higher likelihood of experiencing sleepwalking episodes at least twice a month month.

Brand names for anti-depressants in the SSRI category include Prozac, Zoloft, Paxil, Lexapro and Celexa. Non-prescription sleep aids linked to increased sleepwalking by the Stanford team contained diphenhydramine. Products laced with that chemical include 40 Winks, Simply Sleep, Sleep-Eze, Sominex, Unisom Sleep, Advil PM, and Tylenol PM, according to the National Institutes of Health. 

Chronic sleepwalking also runs (rambles?) within certain families, Ohayon learned: Nearly one-third of individuals who often do it can point to parents, grandparents, uncles, aunts or siblings who have a history of shuffling while slumbering.

To assess the sleepwalking rate in America, Ohayon and his Stanford colleagues used phone interviews conducted with 19,136 randomly selected individuals from 15 states. The participants offered baseline information on their mental health, medical histories and use of medications. They were quizzed on the frequency of any sleepwalking episodes as well as whether they had ever suffered any inappropriate or possibly perilous behaviors while asleep.

What's more, participants were asked if they'd sleepwalked when they were kids and if any family members were known to take unintended, nighttime strolls. In addition to the more more than 3 percent of the U.S. population who sleepwalk chronically, the researchers found that 29.2 percent of the test sample had gone sleepwalking at least once during their lives. 

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Robert Budd, a personal trainer from Southern California, takes sleeping strolls about once a month, as do almost all the men in his family.

Personal trainer Robert Budd figures he sleepwalks about once a month. When he gathers with his kin, sleepwalking lore is a common topic: while seemingly in dreamland, his grandfather once urinated in a friend’s drawer, his uncle often meandered the decks of navy boats, and his dad dismantled tents and ceiling fans.

“All the boys in the family do it,” said Budd, who operates a gym called PHYZYKS in Encinitas, Calif. “I've done it since I was a kid. I would walk out the door and my parents had to grab me and get be back inside. The commonality with my family and myself is it seems to happen when we’re really tired, really drained. When you really need sleep, that’s when you get up and sleepwalk.”

Budd has sleepwalked out of a tent at the Grand Canyon (on the floor, not near the rim). His friends spotted him heading off alone -- apparently wide awake -- but he remembered nothing the next day. While dozing, he once packed for a vacation, even remembering his toothbrush. And there was the night he tried to climb out a second-floor window only to be stopped by the woman who is now his ex-wife.

Was that intended exit possibly symbolic, even for a sleeping man? “It might have been,” Budd said with a laugh.

“It drives my girlfriend drives nuts because sometimes we have conversations and she doesn’t know if I’m awake. Like, I can’t be accountable in the middle of the night.”

Sleepwalkers typically have their eyes open and may speak, making detection tricky. But Ohayon isn’t certain, he said, if they are actually seeing what’s in front of them or if sleepwalkers’ brains have simply mapped out their homes in their minds, allowing them not to bump into walls or furniture. He is sure they’re not dreaming, though, because sleepwalking coincides with a period of “slow-wave sleep” or SWS when brain activity is diminished.

During another sleep phase called REM (rapid eye movement), brain neurons are firing as if a person is awake. This is when you dream. A mechanism within the brain blocks stirring and shifting when you’re in REM sleep, Ohayon said.

“During slow wave sleep, you can move,” he added. “This is an old function of our brain, (possibly a evolutionary leftover). You know, when birds fly, they can sleep with one half of their brain, while the other half is analyzing the flight.

“That is why you see the bird going for thousand of kilometers without any problem. They sleep when they fly.”

Related:

• Sleep paralysis more common in students
• Why do we drool in our sleep?
• Don't make me laugh! I might collapse

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For most people, sleep is undisturbed by the need to pee, because our bladders seem to hold more urine over night. But just how this happens, and why some people are unable to do this, has remained a mystery until now.

New research shows that the body's internal clock controls the production of a key protein that helps regulate the bladder's capacity to hold urine before needing to empty.

The findings may someday yield new therapies to help children who involuntarily wet the bed or adults who frequently wake up at night to urinate, researchers said.

"In certain conditions there may be a derangement of the circadian rhythm so that the wrong amount of [the protein] is produced at the wrong time of day," Andrea Meredith, an assistant professor of physiology at the University of Maryland who was not involved in the study, told LiveScience.

By targeting the protein, called connexin43, researchers may be able to induce the correct amount of the protein at the right times, she said. [ 10 Things You Didn't Know About You ]

 Previous research has shown that mice with an increased amount of connexin43 have a lower functional bladder capacity — that is, their bladders require less liquid before it triggers the need to pee. The researchers in Japan wondered what role the protein plays in normal bladder function and how it's affected by the time of day. While scientists have long known that humans and other animals have day-night differences in functional bladder capacity, it's been unclear if these differences are due to light or if they are governed by an intrinsic circadian (daily) rhythm.

To find out, the researchers needed to determine how much and how often mice urinate throughout the day, a measurement that is more difficult than it sounds. "Mouse urination events are very tiny; it's not as simple as them peeing in a cup, you measuring it and moving on," Meredith explained.

So the researchers developed a machine that constantly moves filter paper beneath a mouse cage to capture the urine — they saw that the mice's day-night urination differences exist even when they are in 24-hour darkness. Moreover, this normal urination pattern was lost in mice with defective biological clocks, showing, for the first time, that urination is an intrinsic circadian rhythm, Meredith said.

The researchers also found that mice with an abnormal connexin43gene, which produces the connexin43 protein, urinate less frequently than normal mice. And when they looked at the bladder muscle cells of normal mice, they found that the expression of the connexin43 gene oscillates throughout the day and is governed by a certain circadian clock molecule.

Taken together, the results show that connexin43, which helps regulate functional bladder capacity, changes according to our biological clocks. If your body is producing the incorrect amount of connexin43 or if your biological clock is off, you may find yourself in the bathroom at night more than you'd like, the study suggests.

"This research explains why healthy people do not urinate during sleep, from the standpoint of bladder function," study co-author and urologist Dr. Akihiro Kanematsu, of the Hyogo College of Medicine in Japan, told LiveScience in an email.

However, both Kanematsu and Meredith stress that other circadian-regulated proteins and genes likely affect functional bladder capacity.

Whatever the case, the research has implications for treating nighttime urination problems in children and the elderly, Kanematsu said. Solving such problems, he explained, may involve looking at the urine production in kidneys and the arousal levels of the brain, in addition to bladder capacity.

"Thus we can conceive to treat these patients from two sides," Kanematsu said. The first approach is to fix the circadian rhythms themselves, either through behavioral means or medications. "The other way is to find therapeutic targets in each organ, like [connexin43] in the bladder."

The study was published today (May 1) in the journal Nature Communications.

More from The Body Odd:

• Should you really have that next cup of coffee?
• Sleep paralysis more common in students
• Night owls have more nightmares

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By Andrew Winner

Wondering if it’s time for another cup of coffee? Just take a look at your iPhone. A new software application from The Pennsylvania State University shows users the optimal time to consume caffeine and when to reach for the decaf.

Dr. Frank Ritter, who created the app along with Dr. Martin Yeh, isn’t trying beat the drum against the country’s coffee habit. Rather, he believes the application’s graphical output presents a novel way for individuals to conceptualize their caffeine consumption.

While it may not kill anyone, caffeine can be a nasty mistress if usage isn’t monitored correctly.

Nervousness and disrupted sleep patterns are just two of the negative consequences of caffeine, with users sometimes becoming so inured to the negative effects of caffeine they aren’t consciously aware of the worsening effects. Additionally, caffeine can have a cumulative effect—too much on Monday could lead to disrupted sleep and grogginess on Tuesday. People attempt to self-correct by increasing their intake on Tuesday, creating a cycle that dramatically affects sleep habits and quality of life.

Caffeine Zone helps individuals understand how long caffeine stays in the system, helping them to avoid such Catch-22s and achieve better sleep.

“Increased levels of caffeine can inhibit normal sleep—at least it does for me,” Ritter said in an e-mail. “A colleague of mine used to talk about using caffeine to fight sleep deprivation, and I think that many of us do that.”

“I have also used the app to avoid caffeine way before a talk so I could have a coffee to hand while giving a talk, and then be able to sleep normally,” Ritter added. “If I had not, I would have had a lot of coffee in anticipation of giving a talk in the afternoon, and would not have gotten rid of the caffeine before bedtime.”

The mobile application prompts users to input their caffeine consumption. Then, using preexisting models of caffeine half-lives, the estimated amount of caffeine in the body is shown on a graph. This allows users to review their caffeine level at a glance – information that could be very useful for those dealing with shift changes at work, for example, or our friends in the Armed Services.

Ritter, of Penn State’s Applied Cognitive Science Lab, was encouraged to study the effects of caffeine by Dr. Susan Chipman with the Office of Navy Research. As one might imagine, the working environment on a submarine lends itself to massive amounts of caffeine intake. Understanding one’s level of caffeine could increase mental acuity and improve quality of life of submariners at sea.

Additionally, the basic platform Ritter created can be extended to monitor different substances. Ritter is also hoping to make caffeine half-life a changeable parameter in the app to account for those who “caffeine” differently.

“This started as an experiment in understanding caffeine and how to deliver and work with mobile apps, but it has grown more than we thought it would,” Ritter said. “We have gotten numerous suggestions from this process and a lot of encouragement.”

With an estimated 80-90 percent of the North American population consuming some amount of caffeine daily and a per-capita usage rate of 280 milligrams for adults, it’s important for the general population to understand the effects of caffeine.

Ritter hopes the app will help educate the public on when a hit of caffeine can improve mental function—and when it can do more harm than good.

Related:

• Tank up on java, release your inner editor
• That coffee buzz is all in your head
• Sleepy people blame others for everything

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A series of strange symptoms known as sleep paralysis may be more common in college students and psychiatric patients, finds a new review study. But the odds of these weird occurrences happening in the general population are less than 8 percent.

Sleep paralysis occurs when you're falling asleep or waking up and you find your body paralyzed, says study author Brian Sharpless. It can be frightening because although your eyes can move, the rest of your body feels like it can't and you have some degree of awareness of this. 

Along with this freaky body sensation, some people may also have hallucinations. "It's sort of like being in a dream while you're awake," explains Sharpless, a clinical assistant professor of psychology at Penn State University.

People in this dream-like state may describe seeing an intruder coming toward them in the bedroom or feeling the pressure of something being on top of their chest. They might feel as though their body is being levitated -- rising up, or say they see themselves outside of their body.

"Even though these hallucinations feel vivid, most of them are over in a few minutes," Sharpless points out.

Different cultures have described the mysteries of sleep paralysis in many colorful ways -- from demons visiting to evil spirits lurking to being abducted by aliens. But the medical explanation may be that it's part of REM (rapid eye movement) sleep that carries over into wakefulness.

To determine how common sleep paralysis is, psychologists analyzed data from 35 different studies. The research, published in the journal Sleep Medicine Reviews, found that roughly 20 percent of the more than 36,000 study participants had at least one episode.

Two groups had higher rates: More than 28 percent of college students and nearly 32 percent of psychiatric patients reported having these odd symptoms at least once.

Although researchers were surprised to find similar rates of sleep paralysis in students and psychiatric patients, both groups tend to have disrupted sleep, which can trigger an episode. Shift workers, jet-lagged travelers, or people with narcolepsy, a sleep disorder, may also experience these quirky -- and spooky -- symptoms because their bedtimes are also frequently interrupted.

In most cases, sleep paralysis is harmless although it can be a strange and scary event, admits Sharpless. But as his results suggest, it's not that uncommon. Even so, if it occurs regularly or is extremely upsetting, you may want to get checked out by a health professional.

Readers, if you've had an episode of sleep paralysis, leave a comment telling us what it was like. We might use your story in an upcoming Body Odd post.

Related:

• 'I've fallen asleep and I can't get up!' 
• Sleep-deprived Americans nap in some strange places
• Why do we drool in our sleep?

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Some of the evidence of a night's sleep are visible when you lift your head off the pillow -- bed head, morning breath, dried-up drool, and eye boogers.

And while the cause of most of these sleep remnants is fairly obvious, the reason behind those sometimes-sticky, sometimes-crusty gobs of crud that can dot the lashes or cling to the corners of the eye is less clear. Why do our peepers churn out this gunk at night and what's in the stuff? For answers to these important questions, Body Odd turned to an eye expert.

"The general consensus is that this debris is the stuff leftover from dried out tears," says Dr. Sherleen Chen, director of the cataract and comprehensive ophthalmology service at Massachusetts Eye and Ear Infirmary in Boston.

Tears are made up of water, protein, oils, and a mucous layer known as mucin, which typically coat the surface of the eye to moisten and protect it from viruses and bacteria.

But when your eyes are closed and your eyelids are not blinking, dirt and debris within the eye isn't continually washed over by tears, which would help to dilute them. So at night, dryness causes the stuff in tears to precipitate out, explains Chen. Then the crud collects toward the inside corner of the eye, where tears usually end up.

Eye boogers can also accumulate on the outer corners of the eye or anywhere along the lash.

Throughout her years of medical training and specializing in ophthalmology, Chen says she's yet to come across a technical term for "eye boogers," so she simply refers to it as "mattering." But in everyday conversation, it may go by the name "sleepy sand," "eye goop," "sleep," or "sleep dust."

There's also the question of its consistency -- sometimes "eye boogers" are wet and sticky and other times they're dry and sandy. Does this depend on how long they've sat there or how much sleep you've gotten?

Chen says the texture is a function of a person's tear film. The crud is crumbly in people whose eyes tend to be dry --  their peepers have more solids and not enough liquid.

Folks who have more allergies, tend to have more mucous, which gives eye crud a wetter, gunkier quality to it.

People who wear contacts are prone to forming more "sleepy sand" because the lenses

irritate the surface of the eye, so it produces more mucous to protect itself. People who have allergies affecting their eyes or who rub them a lot, such as small children, may also have more eye crud.

If the indoor air is dry, you may also wake up with more "sleep dust." Although not an attractive look first thing in the morning, the stuff is basically harmless.

Chen says the best way to clear eye boogers is to lay a hot washcloth on the lid and lashes for a minute or two, then gently clean them off.

What do you call "eye boogers?" Ever had a particularly bad case of 'em?

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She must be the early-to-bed, early-to-rise type.

The early bird might catch the worm because it sleeps better than the night owl, not just because it awakens earlier.

At least that appears to be the case for humans, according to a new study.

Researchers found that night owls -- “evening-type individuals”-- are significantly more likely to suffer from poor sleep quality, daytime sleepiness and disturbing nightmares than early birds -- “morning-type individuals”-- or folks whose bedtime falls somewhere between the two.

“Evening-type people have more nightmares because of their sleep patterns,” says lead author Yavuz Selvi, assistant professor of psychiatry at Yuzuncu Yil University in Van, Turkey, whose paper was published online Aug. 25 in the journal Sleep and Biological Rhythms.

Staying awake late at night and waking up late in the morning disrupts the relationship between the body’s internal clock and its ability to maintain normal sleep patterns, Selvi explains. In other words, it really screws up your circadian rhythm.

Nightmares usually awaken you, so if they occur frequently, you might begin to fear falling asleep, cutting into your snooze time even more. Epidemiological studies have found that nearly nine in 10 adults reporting having at least one nightmare in the previous year, Selvi says, with 2 percent to 6 percent reporting weekly nightmares.

He and his coauthors studied 264 medical students, ages 17 to 26 years old, who weren’t yet dealing with crazy hours in their training. The researchers administered a battery of tests to assess whether the students were morning or evening types, the quality of their sleep and how frequently they experienced nightmares and how disturbing they were.

The “Morningness-Eveningness Questionnaire” taken by the students asked what time they’d go to bed and get up if they were entirely free to plan their day and evening. Other questions touched on such matters as what time they’d prefer to hit the gym and how wide-awake they feel when they get up in the morning.

 The test revealed that 59 of the students were evening types, 67 morning types and the rest fell in the “intermediate” range. Men were more likely than women to be night owls; vice versa when it came to early birds.

As a self-described night owl, I wasn’t thrilled to learn from Selvi that the consequences of my sleep habits could go way beyond my morning sluggishness and frequent urge to nap.

“A possible relationship has emerged between eveningness and certain mental disorders, including substance abuse, bulimia, sleep disorders, attention deficit/hyperactivity disorder, suicidality and mood disorders,” he told me.

 One reason night owls tend to get stressed out, Selvi says, is because it’s tough to hold a job or attend classes if your brain doesn’t kick in until noon or so.

 Yikes. How about you? Are you a night owl, an early bird or something in between? Would you like to change your sleep habits, or does your pattern work for you?

Related:

• Sleep-deprived Americans nap in some weird places 
• Why do we drool in our sleep?
• Hammock naps are the best, research proves

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We're sure you never drool in your sleep. But if your ... friend ... ever does, Women's Health magazine contributor Dr. Keri Peterson has some helpful advice. Peterson, a board-certified internist, appeared on TODAY this morning to tell us some reasons why this might be happening, and what you can do to knock it off.

"When you sleep, your muscles relax, your mouth falls open, and if you're lying on your side, it's gonna leak out," explains Peterson, adding this fun fact: We make a liter of saliva a day.

"Also, if you have sinus problems, or allergies, and you tend to mouth-breathe, you're gonna be more likely to have this happen to you," she continues.

To keep yourself from drooling all over your pillow -- try sleeping on your back, Peterson advises. Watch the video for more on this, plus answers to more embarrassing health questions.

Got an embarrassing health question of your own? Ask us in a comment -- a writer for The Body Odd may answer it in an upcoming post.

Follow msnbc.com health writer on Twitter: @melissadahl.

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Uh oh, she's yawning. Jerk alert!

The next time your boss scolds you for low production and claims that as the reason for not giving you a well-deserved raise, she may not be unfair. She may be sleepy.

A new study shows that when people, in this case college students, are sleepy they are more likely to think about how events could have turned out differently and ponder how situations could have been better. Depending on the outcome, they may blame others and even seek revenge. Researchers call this sleepy thinking ‘counterfactual.’

Irritability, moodiness and complaining are well researched side effect of sleepiness, but the new study is believed to be the first to explore how people actually think when they’re sleepy, says principal investigator David Mastin, associate professor of psychology at the University of Arkansas at Little Rock. He presented the abstract last week at SLEEP 2011, the 25^th anniversary meeting of the Associated Professional Sleep Societies in Minneapolis.

“We need to realize that sleep deprivation is debilitating,” he says. “It causes people to have car accidents and make poor judgments. Would you want your supervisor reviewing you for a promotion when they are sleepy? They may say, ‘Quarterly sales were down last month and whose fault was that?’ If they are sleepy, they are more likely to seek revenge and not give you that raise.

“You hope the state trooper who pulls you over has had enough sleep. Now we can imagine how important it can be to understand how not having enough sleep affects us, the impact it can have on our marriages, the way we treat people in the workplace. During voir dire, should lawyers ask jurors how sleepy they are?” 

Sherri Williams, a first-year mass communications Ph.D. student at Syracuse University, says she realized her thinking was stinking last week after she stayed up overnight to complete class work. She found herself mad at the world.

“I was extra aggravated by everything people did,” acknowledges Williams, 38. “I was mad at the phone company for charging me $120 to talk and text, and for having to pay $100 to watch TV each month. Then I remembered I had been awake for 27 hours.”

Mastin says other cultures, such as Latin cultures, seem to understand what Americans don’t: Getting enough sleep is vital for a quality life.

“They have siesta periods; in our culture we almost regard taking naps as childish,” he says. “As psychologists, we want to understand the human condition, and we should know what’s going on when people are sleepy.”

These study results mean researchers will focus more attention on people in professions that often require them to sacrifice sleep.

“Having no sleep can affect our motor coordination and can be as dangerous as driving under the influence of alcohol,” Mastin explains. “So we’re starting to pay attention to truck drivers and air plane pilots and physicians who are sleepy. We would never tolerate somebody being drunk in the workplace. But sleepy? We don’t give it a second thought.”

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Ahhh.

Ever notice that you sleep like a baby on a hammock? Maybe it's just the slow, soothing rocking motion that reminds grown-ups of being in a parent's arms until their little eyelids finally close.

Inspired by that concept, some Swiss scientists decided to examine the idea of rocking a person to sleep. Researchers wondered whether the see-sawing movement would make adults drift off sooner and how it affected sleep quality.

So they developed an "experimental hammock" -- a custom-made bed that gently swayed from side to side. They asked 12 participants, all of them men ages 22 to 38, who were all good sleepers, to take a 45-minute afternoon nap in this cradle for grown-ups.

They monitored the volunteers' brain waves throughout the nap and compared the results to having these same participants nap in the same bed without any rocking motion. The research appears in the June 21 issue of Current Biology.

"We observed a faster transition to sleep in each and every participant in the swinging condition," says Sophie Schwartz, a neuroscientist at the Sleep and Cognition Neuroimaging Lab at the University of Geneva in Switzerland and the study's lead author.

"Not only does rocking make us fall asleep more quickly, but it also makes people sleep more deeply throughout the nap," she explains.

Compared to nodding off in a stationary bed, those napping in a swinging one had a longer duration of N2 sleep, a type of non-rapid eye movement sleep that makes up about half a night's shuteye. Scientists also observed a dramatic boost in brain-wave patterns seen in deep sleep. 

"Motion has specific effects on the brain, and this is precisely what our study shows," says Schwartz. Although researchers expected that rocking would make volunteers conk out sooner, they were surprised it changed the quality of sleep and in such a sustained manner.

Now that they've seen how rocking affects a short nap in healthy adults, the next step is to see how it benefits an entire night's sleep. Other questions they might research include whether the brain changes seen in adults from rocking are also observed in babies, whether motion improves sleep in those with insomnia, and whether it has positive effects on waking performance.

Still there's no need to wait for answers. This summer, put science to the test: Find yourself a hammock or rocking chair in the shade and enjoy that time-honored tradition in some cultures -- the siesta.

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Sleepyheads, please refrain from licking your monitor.

Slacking off on shuteye could make it harder for you to resist high-calorie treats and fattening foods, new research found.

Feeling drowsier during the day because you didn't catch enough ZZZs at night may make it easier for you to give in to temptation, suggests a preliminary study to be presented at the 2011 meeting of the Associated Professional Sleep Societies.

In this small study of 12 healthy adults, ages 19 to 45, participants were shown photographs of low- or high-calorie foods over a four-minute period as images of their brains were scanned. Volunteers were told they would be given a memory test afterward to make them focus on the visuals.

Every few seconds new images would flash before participant's eyes including such healthy fare as salads, fresh fish, an apple or orange. They also saw more enticing edibles from strawberry cheesecake and french fries to cheeseburgers and chocolate cake. As a control, researchers sprinkled in shots of trees, rocks, and flowers.

Volunteers also completed questionnaires about how drowsy they were during the day as well as their food likes and dislikes and typical eating habits.

Scientists found that "the sleepier you are, the less the prefrontal cortex -- the inhibitory area of the brain -- is activated when it's shown high-calorie foods," says William Killgore, an assistant professor of psychology at Harvard Medical School and McLean Hospital in Belmont, Mass.

In other words, if you've skimped on sleep, you're less likely to put on the brakes when you're around fattening foods. And you're more likely to reach out and grab that bacon double cheeseburger or dig into a pint of Chunky Monkey.

In the research, participants were not chronically sleep-deprived. They had the usual tiredness that comes from staying up past their bedtime by an hour or two a night. Even this was strongly correlated with less activation in the inhibitory areas of the brain when shown calorie-rich foods.

When you don't get the rest you need, "you might not have the ability to say no to that extra cookie or dessert," points out Killgore, and you're a little more likely to take in a few extra calories a day.

"Even subtle changes in sleep could be having larger effects in ways we hadn't considered, such as appetite, body weight, and food choices," explains Killgore. A little bit of sleep loss adds up and may influence your body shape. 

"It's entirely plausible that with less inhibitory control, you reach for less optimal foods, and this may lead to a lot more weight over a lifetime," Killgore says.

And a fatigue-induced lack of inhibition can extend to behaviors beside eating. Other studies have suggested that being sleep deprived affects a person's ability to plan and think ahead, and skews judgment when assessing risk.

When you're tired during the day, are you more likely to go for junk food?

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Scientists may have found an explanation for all those slip-ups we make when we haven’t gotten enough sleep.

A new study shows that even when we feel wide awake, regions of our brains may be opting to go offline in a sort of rolling blackout similar to what the electric company does when demands for power spike. 

Though the study was in rats, its results should be applicable to humans, said Dr. Chiara Cirelli, a co-author on the study and an associate professor in the department of psychiatry at the University of Wisconsin at Madison.

When it comes to the mechanics of sleeping and waking brains, there isn’t a whole lot of difference between humans and rats, Cirelli said.

To learn what happens in the brains of the sleep deprived, Cirelli and her colleagues wired up the rats’ brains. By implanting electrodes in brain tissue the researchers would then be able to monitor what individual neurons were doing.

Some of the electrodes were positioned deep in the rats’ brains, which means that the experiment will be difficult to duplicate in humans.

The researchers kept the rodents awake long past their “bedtimes,” by dropping fun toys into the rats’ cages. Though they were tired, the rats would continue to play for hours with the novel toys.

As the rats played, the researchers watched what was happening in the rodents’ brains. What they saw surprised them: nerve cells would be sparking one minute and then go completely silent in a kind of nap phase.

You couldn’t tell this was happening by watching the rats playing -- they all looked perfectly normal. But subtle differences showed up when the researchers gave the rats a task to perform.

The rats had been taught to access sugar pellets by reaching through a hole in their cages with just one paw. Getting a pellet through the hole and into the cage takes a lot of concentration and dexterity, Cirelli said. Normally the rats would be able to do this over and over again, only rarely dropping a pellet.

But rats that were sleep-deprived had much less success getting the pellets into their cages.  And when researchers watched what was happening in the rats’ brains, they saw that the mistakes happened when nerve cells went offline in the region that controls movement.

The rats weren’t consistently bad at what they were doing -- one minute they’d be able to pull a sugar pellet in and the next they’d slip up. And therein lies the danger of getting too little sleep, Cirelli said.

Think about driving – or air traffic controllers – she said. You might be going along just fine and then need to make a split-second decision when the wrong brain circuits go offline to catnap. The result could be catastrophic: a downed plane or a driver switching into a lane that already has a car in it. And yet another reason to get your Zzzz’s.

Ever had any funny (or scary) slip-ups when your snooze-time was curtailed? Tell us about it, below.

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