Sleeping
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Napping reverses health effects of poor sleep, study finds
A short nap can help relieve stress and bolster the immune systems of men who slept only two hours the previous night, according to a new study published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism (JCEM).
Lack of sleep is recognized as a public health problem. Insufficient sleep can contribute to reduced productivity as well as vehicle and industrial accidents, according to the U.S. Centers for Disease Control and Prevention. In addition, people who sleep too little are more likely to develop chronic diseases such as obesity, diabetes, high blood pressure and depression.
Nearly three in 10 adults reported they slept an average of six hours or less a night, according to the National Health Interview Survey.
"Our data suggests a 30-minute nap can reverse the hormonal impact of a night of poor sleep," said one of the JCEM study's authors, Brice Faraut, PhD, of the Université Paris Descartes-Sorbonne Paris Cité in Paris, France. "This is the first study that found napping could restore biomarkers of neuroendocrine and immune health to normal levels."
The researchers used a cross-over, randomized study design to examine the relationship between hormones and sleep in a group of 11 healthy men between the ages of 25 and 32. The men underwent two sessions of sleep testing in a laboratory, where meals and lighting were strictly controlled.
During one session, the men were limited to two hours of sleep for one night. For the other session, subjects were able to take two, 30-minute naps the day after their sleep was restricted to two hours. Each of the three-day sessions began with a night where subjects spent eight hours in bed and concluded with a recovery night of unlimited sleep.
Researchers analyzed the participants' urine and saliva to determine how restricted sleep and napping altered hormone levels. After a night of limited sleep, the men had a 2.5-fold increase in levels of norepinephrine, a hormone and neurotransmitter involved in the body's fight-or-flight response to stress. Norepinephrine increases the body's heart rate, blood pressure and blood sugar. Researchers found no change in norepinephrine levels when the men had napped following a night of limited sleep.
Lack of sleep also affected the levels of interleukin-6, a protein with antiviral properties, found in the subjects' saliva. The levels dropped after a night of restricted sleep, but remained normal when the subjects were allowed to nap. The changes suggest naps can be beneficial for the immune system.
"Napping may offer a way to counter the damaging effects of sleep restriction by helping the immune and neuroendocrine systems to recover," Faraut said. "The findings support the development of practical strategies for addressing chronically sleep-deprived populations, such as night and shift workers."
Other authors of the study include: Samir Nakib, Catherine Drogou, Maxime Elbaz, Fabien Sauvet, Jean-Pascal De Bandt and Damien Léger of the Université Paris Descartes-Sorbonne Paris Cité.
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Study Shows How Sleep Improves Memory
BOSTON -- A good night's sleep triggers changes in the brain that help to improve memory, according to a new study led by researchers at Beth Israel Deaconess Medical Center (BIDMC).
These findings, reported in the June 30, 2005, issue of the journal Neuroscience and currently published on-line, might help to explain why children -- infants, in particular -- require much more sleep than adults, and also suggest a role for sleep in the rehabilitation of stroke patients and other individuals who have suffered brain injuries.
"Our previous studies demonstrated that a period of sleep could help people improve their performance of 'memory tasks,' such as playing piano scales," explains the study's lead author Matthew Walker, PhD, director of BIDMC's Sleep and Neuroimaging Laboratory. "But we didn't know exactly how or why this was happening.
"In this new research, by using functional magnetic resonance imaging (fMRI), we can actually see which parts of the brain are active and which are inactive while subjects are being tested, enabling us to better understand the role of sleep to memory and learning."
New memories are formed within the brain when a person engages with information to be learned (for example, memorizing a list of words or mastering a piano concerto). However, these memories are initially quite vulnerable; in order to "stick" they must be solidified and improved. This process of "memory consolidation" occurs when connections between brain cells as well as between different brain regions are strengthened, and for many years was believed to develop merely as a passage of time. More recently, however, it has been demonstrated that time spent asleep also plays a key role in preserving memory.
In this new study, twelve healthy, college-aged individuals were taught a sequence of skilled finger movements, similar to playing a piano scale. After a 12- hour period of either wake or sleep, respectively, the subjects were tested on their ability to recall these finger movements while an MRI measured the activity of their brain.
According to Walker, who is also an Assistant Professor of Psychiatry at Harvard Medical School, the MRI results showed that while some areas of the brain were distinctly more active after a period of sleep, other areas were noticeably less active But together, the changes brought about by sleep resulted in improvements in the subjects' motor skill performance
"The cerebellum, which functions as one of the brain's motor centers controlling speed and accuracy, was clearly more active when the subjects had had a night of sleep," he explains. At the same time, the MRIs showed reduced activity in the brain's limbic system, the region that controls for emotions, such as stress and anxiety.
"The MRI scans are showing us that brain regions shift dramatically during sleep," says Walker. "When you're asleep, it seems as though you are shifting memory to more efficient storage regions within the brain. Consequently, when you awaken, memory tasks can be performed both more quickly and accurately and with less stress and anxiety."
The end result is that procedural skills -- for example, learning to talk, to coordinate limbs, musicianship, sports, even using and interpreting sensory and perceptual information from the surrounding world -- become more automatic and require the use of fewer conscious brain regions to be accomplished.
This new research may explain why children and teenagers need more sleep than adults and, in particular, why infants sleep almost round the clock.
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Forget all-night studying, a good night's sleep is key to doing well on exams
As fall semesters wind down at the country's colleges and universities, students will be pulling all-night study sessions to prepare for final exams. Ironically, the loss of sleep during these all-nighters could actually work against them performing well, says a Harris Health System sleep specialist.
Dr. Philip Alapat, medical director, Harris Health Sleep Disorders Center, and assistant professor, Baylor College of Medicine, recommends students instead study throughout the semester, set up study sessions in the evening (the optimal time of alertness and concentration) and get at least 8 hours of sleep the night before exams.
"Memory recall and ability to maintain concentration are much improved when an individual is rested," he says. "By preparing early and being able to better recall what you have studied, your ability to perform well on exams is increased."
As head of the Harris Health Sleep Disorders Center, a nationally certified facility by the American Academy of Sleep Medicine, Alapat and his staff perform about 1,200 sleep studies a year to evaluate patients for a variety of sleep disorders, including apnea, insomnia, restless legs syndrome, narcolepsy and chronic fatigue syndrome.
College-aged students ideally should get 8-9 hours of sleep a night. Truth is, most students generally get much less.
"Any prolonged sleep deprivation will affect your mood, energy level and ability to focus, concentrate and learn, which directly affects your academic performance," Alapat adds.
Throw in the occasional all-nighter, consumption of caffeinated beverages like coffee, tea or energy drinks, and students are at risk for developing insomnia, as well as increased risks for alcohol abuse and motor vehicle accidents.
"A lot of college students graduate high school and leave the protective family environment where they have curfews or set bed times," Alapat says. "In college, they don't have these guidelines for sleep and recognize that they can stay up late. This likely contributes to the sleep deprivation seen commonly in college students."
Alapat's recommendations:
• Get 8-9 hours of sleep nightly (especially before final exams)
• Try to study during periods of optimal brain function (usually around 6-8 p.m.)
• Avoid studying in early afternoons, usually the time of least alertness
• Don't overuse caffeinated drinks (caffeine remains in one's system for 6-8 hours)
• Recognize that chronic sleep deprivation may contribute to development of long-term diseases like diabetes, high blood pressure and heart disease
If suffering from bouts of chronic sleep deprivation or nightly insomnia that lasts for more than a few weeks, Alapat suggests consulting a sleep specialist.
"Sleep appears to play a key role in human development," says Walker. "At 12 months of age, infants are in an almost constant state of motor skill learning, coordinating their limbs and digits in a variety of routines. They have an immense amount of new material to consolidate and, consequently, this intensive period of learning may demand a great deal of sleep."
The new findings may also prove to be important to patients who have suffered brain injuries, for example, str