A collection of studies published last Wednesday in the journal Sleep tackled some important questions: What are the health effects of not getting enough sleep? How does sleep deprivation affect teens? Does insomnia have long-term consequences?
Credit: Time Magazine
Given that past research has shown that short sleepers (and unusually long sleepers) die younger than people who get to hours per night, a new Penn State study looked at the impact of insomnia on mortality. The consequences could be dire: the study of men and women in Pennsylvania found that insomniac men who slept less than hours per day were four times more likely to die than those who got a full night’s rest. The study even adjusted for other medical conditions that affect sleep (and death rates), such as obesity, alcohol and depression. Of note, sleep deprivation did not affect women’s mortality.
In another study in Sleep, University of Sydney researchers focused on adolescents and young adults who weren’t getting enough sleep — an increasingly common problem among the digital generation, who stays up late plugged into their computers and smart phones. Turns out, burning the midnight oil can have long-term consequences. Researchers found that for each hour of lost sleep, levels of psychological distress rose by % in nearly -to--year-olds who were followed for to months. Overall, short sleepers were % more likely to report symptoms of psychological distress on a standard test, compared with people who got adequate sleep. The effect was especially pronounced among young people who already suffered from anxiety; in this group, lack of sleep triggered more serious mental health problems like full-blown depression and even bipolar disorder, according to the study’s lead author, Professor Nick Glozier. But even among those who began the study in good health, less than five hours of sleep meant tripling their odds of psychological distress.
A third Sleep study this week found that teens who didn’t get enough z’s consumed more calories than their well-rested peers. The study of adolescents, average age , revealed that teenagers who slept less than hours a night on weeknights ate % more calories from fat per day and % more calories from carbs than teens who slept longer. They also tended to get their calories from snacks instead of healthful meals. Cumulatively, this behavior increases the risk of obesity and, in turn, the chances of developing cardiovascular disease later in life.
The American Academy of Sleep Medicine suggests that adults get an average of seven to eight hours of sleep per night, while the National Sleep Foundation recommends that adolescents need at least hours, though only % of them get enough.
“Sleep disorders are common in the general population and even more so in clinical practice, yet are relatively poorly understood by doctors and other health care practitioners,” wrote Sue Wilson, the lead author of new guidelines published today by the British Association of Psychopharmacology to help doctors treat insomnia and other sleep disorders. Her advice: get a diagnosis from a sleep specialist for patients, then try behavioral therapy to improve their sleep before jumping to prescription medication. Most of all, pay attention to who you are treating: postmenopausal women might need hormone therapy, small children with ADHD might require melatonin treatment.
And if you suffer from disordered sleep patterns, consider these tips from the National Sleep Foundation:
Avoid caffeine. Tea, coffee, soda and energy drinks can keep you awake for up to hours. Instead, when your mid-afternoon slump hits, try an energizing snack like nuts or yogurt.
Nest. Make your bed as comfortable as possible. Keep your sleep environment dark, cool and work-free.
Establish a routine. About an hour before bedtime, start a nightly relaxation routine that can include reading, taking a bath or anything else that soothes you. Complete all exercise at least three hours before bedtime. Don’t look at screens before you go to sleep, which can stimulate your brain.
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It is by now well established that sleep can be an important tool when it comes to enhancing memory and learning skills. And now, a new study sheds light on the role that dreams play in this important process.
Led by scientists at Beth Israel Deaconess Medical Center (BIDMC), the new findings suggest that dreams may be the sleeping brain’s way of telling us that it is hard at work on the process of memory consolidation, integrating our recent experiences to help us with performance-related tasks in the short run and, in the long run, translating this material into information that will have widespread application to our lives. The study is reported in the April 22 On-line issue of Current Biology.
“What’s got us really excited, is that after nearly 100 years of debate about the function of dreams, this study tells us that dreams are the brain’s way of processing, integrating and really understanding new information,” explains senior author Robert Stickgold, PhD, Director of the Center for Sleep and Cognition at BIDMC and Associate Professor of Psychiatry at Harvard Medical School. “Dreams are a clear indication that the sleeping brain is working on memories at multiple levels, including ways that will directly improve performance.”
At the outset, the authors hypothesized that dreaming about a learning experience during nonrapid eye movement (NREM) sleep would lead to improved performance on a hippocampus-dependent spatial memory task. (The hippocampus is a region of the brain responsible for storing spatial memory.)
To test this hypothesis, the investigators had 99 subjects spend an hour training on a “virtual maze task,” a computer exercise in which they were asked to navigate through and learn the layout of a complex 3D maze with the goal of reaching an endpoint as quickly as possible. Following this initial training, participants were assigned to either take a 90-minute nap or to engage in quiet activities but remain awake. At various times, subjects were also asked to describe what was going through their minds, or in the case of the nappers, what they had been dreaming about. Five hours after the initial exercise, the subjects were retested on the maze task.
The results were striking.
The non-nappers showed no signs of improvement on the second test – even if they had reported thinking about the maze during their rest period. Similarly, the subjects who napped, but who did not report experiencing any maze-related dreams or thoughts during their sleep period, showed little, if any, improvement. But, the nappers who described dreaming about the task showed dramatic improvement, 10 times more than that shown by those nappers who reported having no maze-related dreams.
“These dreamers described various scenarios – seeing people at checkpoints in a maze, being lost in a bat cave, or even just hearing the background music from the computer game,” explains first author Erin Wamsley, PhD, a postdoctoral fellow at BIDMC and Harvard Medical School. These interpretations suggest that not only was sleep necessary to “consolidate” the information, but that the dreams were an outward reflection that the brain had been busy at work on this very task.
Of particular note, say the authors, the subjects who performed better were not more interested or motivated than the other subjects. But, they say, there was one distinct difference that was noted.
“The subjects who dreamed about the maze had done relatively poorly during training,” explains Wamsley. “Our findings suggest that if something is difficult for you, it’s more meaningful to you and the sleeping brain therefore focuses on that subject – it ‘knows’ you need to work on it to get better, and this seems to be where dreaming can be of most benefit.”
Furthermore, this memory processing was dependent on being in a sleeping state. Even when a waking subject “rehearsed and reviewed” the path of the maze in his mind, if he did not sleep, then he did not see any improvement, suggesting that there is something unique about the brain’s physiology during sleep that permits this memory processing.
“In fact,” says Stickgold, “this may be one of the main goals that led to the evolution of sleep. If you remain awake [following the test] you perform worse on the subsequent task. Your memory actually decays, no matter how much you might think about the maze.
“We’re not saying that when you learn something it is dreaming that causes you to remember it,” he adds. “Rather, it appears that when you have a new experience it sets in motion a series of parallel events that allow the brain to consolidate and process memories.”
Ultimately, say the authors, the sleeping brain seems to be accomplishing two separate functions: While the hippocampus is processing information that is readily understandable (i.e. navigating the maze), at the same time, the brain’s higher cortical areas are applying this information to an issue that is more complex and less concrete (i.e. how to navigate through a maze of job application forms).
“Our [nonconscious] brain works on the things that it deems are most important,” adds Wamsley. “Every day, we are gathering and encountering tremendous amounts of information and new experiences,” she adds. “It would seem that our dreams are asking the question, ‘How do I use this information to inform my life?’”
Study coauthors include BIDMC investigators Matthew Tucker, Joseph Benavides and Jessica Payne (currently of the University of Notre Dame).
This study was supported by grants from the National Institutes of Health.
BIDMC is a patient care, teaching and research affiliate of Harvard Medical School, and consistently ranks in the top four in National Institutes of Health funding among independent hospitals nationwide. BIDMC is a clinical partner of the Joslin Diabetes Center and a research partner of the Dana-Farber/Harvard Cancer Center. BIDMC is the official hospital of the Boston Red Sox.
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BERKELEY — If you see a student dozing in the library or a co-worker catching winks in her cubicle, don’t roll your eyes. New research from the University of California, Berkeley, shows that an hour’s nap can dramatically boost and restore your brain power. Indeed, the findings suggest that a biphasic sleep schedule not only refreshes the mind, but can make you smarter.
Conversely, the more hours we spend awake, the more sluggish our minds become, according to the findings. The results support previous data from the same research team that pulling an all-nighter — a common practice at college during midterms and finals — decreases the ability to cram in new facts by nearly percent, due to a shutdown of brain regions during sleep deprivation.
“Sleep not only rights the wrong of prolonged wakefulness but, at a neurocognitive level, it moves you beyond where you were before you took a nap,” said Matthew Walker, an assistant professor of psychology at UC Berkeley and the lead investigator of these studies.
In the recent UC Berkeley sleep study, healthy young adults were divided into two groups — nap and no-nap. At noon, all the participants were subjected to a rigorous learning task intended to tax the hippocampus, a region of the brain that helps store fact-based memories. Both groups performed at comparable levels.
At p.m., the nap group took a -minute siesta while the no-nap group stayed awake. Later that day, at p.m., participants performed a new round of learning exercises. Those who remained awake throughout the day became worse at learning. In contrast, those who napped did markedly better and actually improved in their capacity to learn.
Matthew Walker, assistant psychology professor, has found that a nap clears the brain to absorb new information.
These findings reinforce the researchers’ hypothesis that sleep is needed to clear the brain’s shor
t-term memory storage and make room for new information, said Walker, who presented his preliminary findings on Sunday, Feb. , at the annual meeting of the American Association of the Advancement of Science (AAAS) in San Diego, Calif.
Since 2007, Walker and other sleep researchers have established that fact-based memories are temporarily stored in the hippocampus before being sent to the brain’s prefrontal cortex, which may have more storage space.
“It’s as though the e-mail inbox in your hippocampus is full and, until you sleep and clear out those fact e-mails, you’re not going to receive any more mail. It’s just going to bounce until you sleep and move it into another folder,” Walker said.
In the latest study, Walker and his team have broken new ground in discovering that this memory-refreshing process occurs when nappers are engaged in a specific stage of sleep. Electroencephalogram tests, which measure electrical activity in the brain, indicated that this refreshing of memory capacity is related to Stage non-REM sleep, which takes place between deep sleep (non-REM) and the dream state known as Rapid Eye Movement (REM). Previously, the purpose of this stage was unclear, but the new results offer evidence as to why humans spend at least half their sleeping hours in Stage , non-REM, Walker said.
“I can’t imagine Mother Nature would have us spend percent of the night going from one sleep stage to another for no reason,” Walker said. “Sleep is sophisticated. It acts locally to give us what we need.”
Walker and his team will go on to investigate whether the reduction of sleep experienced by people as they get older is related to the documented decrease in our ability to learn as we age. Finding that link may be helpful in understanding such neurodegenerative conditions as Alzheimer’s disease, Walker said.
In addition to Walker, co-investigators of these new findings are Bryce A. Mander and psychology undergraduate Sangeetha Santhanam.http://www.berkeley.edu
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