Chapter 10. Biological Rhythms and Sleep
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By Scicurious It seems like the worst sort of cycle. The less sleep you get, the less effective you are. Then you have more to do, get more stressed, and stay up trying to get it all done (or lie awake stressing about it). The next day, less sleep, and even more anxiety. The ironic part is that you might not be quite so anxious…if you could just get some SLEEP. The authors of this study wanted to look at anxiety responses in people, and how they were affected by lack of sleep. To do this, you need 19 healthy participants, an fMRI machine, a test of anxiety…and way to keep people up all night. How do you assess anxiety responses? Start with cues, and then give outcomes. You can see the layout of the studies above. The participants were placed in an fMRI scanner. During the recording, they were shown signs, followed by stimuli. If they got a negative sign, they would always get a negative stimuli (a man with a gun, which is plenty good enough to provoke an anxiety response). If they got a zero sign, they got a normal stimuli (a doorknob. Nothing scary there). If they got a question mark, they have a 50% chance of getting the negative stimulus. This question mark gives you an ambiguous stimulus, you don’t know what to expect. They had the participants go through the series of stimuli in two conditions: rested and sleep deprived. And when they sleep deprived them, BOY did they. Many sleep deprivation studies will restrict sleep to, say, 4 hours the night before the study, or 5. Not these guys. No, they had the participants pull an all-nighter! © 2013 Scientific American
by Kelly Servick It almost seems like a mystical correlation. Babies conceived at certain times of the year appear healthier than those conceived during other times. Now, scientists have shown that the bizarre phenomenon is actually true—and they think they may know why it happens. The work is "a really long-overdue analysis," says economist Douglas Almond of Columbia University, who was not involved in the study. "This is maybe not quite a smoking gun," he says, "but it's much stronger than the previous evidence." As early as the 1930s, researchers noticed that children born in winter were more prone to health problems later in life: slower growth, mental illness, and even early death. Among the proposed explanations were diseases, harsh temperatures, and higher pollution levels associated with winter, when those expectant mothers and near-term fetuses might be most vulnerable. But recently, as economists looked at demographics, the picture got more complicated. Mothers who are nonwhite, unmarried, or lack a college education are more likely to have children with health and developmental problems. They are also more likely to conceive in the first half of the year. That made it hard to tease out the socioeconomic effects from the seasonal ones. Economists Janet Currie and Hannes Schwandt of Princeton University took a new approach to resolving this long-standing question, using data from the vital statistics offices in New Jersey, New York, and Pennsylvania about births between 1994 and 2006. To control for socioeconomic status, their study looked only at siblings born to the same mother. And lo and behold, seasonal patterns persist, they report online today in the Proceedings of the National Academy of Sciences. © 2010 American Association for the Advancement of Science
By Michelle Roberts Health editor, BBC News online Late nights and lax bedtime routines can blunt young children's minds, research suggests. The findings on sleep patterns and brain power come from a UK study of more than 11,000 seven-year-olds. Youngsters who had no regular bedtime or who went to bed later than 21:00 had lower scores for reading and maths. Lack of sleep may disrupt natural body rhythms and impair how well the brain learns new information say the study authors. They gathered data on the children at the ages of three, five and then seven to find out how well they were doing with their learning and whether this might be related to their sleeping habits. Erratic bedtimes were most common at the age of three, when around one in five of the children went to bed at varying times. By the age of seven, more than half the children had a regular bedtime of between 19:30 and 20:30. Overall, children who had never had regular bedtimes tended to fare worse than their peers in terms of test scores for reading, maths and spatial awareness. The impact was more obvious throughout early childhood in girls than in boys and appeared to be cumulative. BBC © 2013
Melatonin is marketed as a natural sleep aid but it's potentially risky for healthy children to use long term, Canadian pediatricians say. Difficulties settling, falling asleep and staying asleep affect up to 25 per cent of children generally and up to half of those with physical and mental health problems, according to the Canadian Sleep Society. Melatonin is a hormone of darkness that is part of the sleep cycle. People can buy melatonin supplements at pharmacies and health food stores to overcome jet lag or occasional insomnia. But long-term use by healthy, developing children isn't advised, said Dr. Shelly Weiss, a neurologist at the Hospital for Sick Children in Toronto, who is studying the use of melatonin supplements for improving sleep in children with epilepsy. "It's being touted as this magic pill," said Weiss. "There's definitely concern that people are going to use it more widely and not appreciate that their child can learn to sleep better without a hormone being given." Melatonin supplements contain between 25 to 50 times as much melatonin as the body makes at night, Weiss noted. "There's definitely potential risk, mostly to delayed puberty or delayed development in children who have taken it for a long time," said Weiss, who is also president of the Canadian Sleep Society and an associate professor at the University of Toronto. © CBC 2013
A UC Berkeley study suggests that sleep deprivation triggers anxiety by inducing hyperactivity in brain regions that control emotions. The study, published in the Journal of Neuroscience, suggests that sleep therapy can help patients with anxiety disorders. Stress and anticipation bring anxiety that can sometimes be good; if under control, anxiety might help a person focus and be more efficient. But a patient with anxiety disorders, such as post-traumatic stress disorder (PTSD), generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD) or other disorders and phobias, cannot control it. The feeling of anxiety and nervousness is constant and has major negative impact on their everyday life. The socioeconomic impact is huge as about one in five adults in the U.S. are affected by such mental illnesses. What are the drivers of anxiety disorders? Why can some people control anxiety while others cannot? Research studies have shown over the years that causes can be genetics, personality, social environment and brain chemistry. Scientists have found a network of neurons in the brain that supports affective anticipation and anxiety. More precisely, those with anxiety disorders have hyperactivity in certain regions of the brain that process emotions, including the amygdala and anterior insula cortex. On top of that, sleep deprivation amplifies the symptoms, a setback for patients because it is very common for them to suffer from sleep abnormalities. Looking for more clues about the connection between sleep and anxiety management, Matthew P. Walker, professor of psychology and neuroscience at UC Berkeley, led a study that looked for differences in the activity of the amygdala and anterior insula cortex in the brains of healthy adults after sleep deprivation and after a good night’s sleep.
Till Roenneberg Sleep is essential for health, performance and wellbeing. Yet in many countries, people are getting one to two hours less of it each night than their ancestors did 50–100 years ago. Even when people have the opportunity to sleep, many cannot. Sleep pathologies are approaching epidemic levels, affecting an estimated 70 million people in the United States alone (see go.nature.com/6dgqhg). And in some countries, direct and indirect costs of sleep-related problems are thought to approach 1% of gross domestic product1. Despite these alarming numbers, sleep research ranks only 91st in the 235 categories on this year's funding list of the US National Institutes of Health — below, for instance, studies of tobacco (see go.nature.com/ces1rf). Researchers have made great advances in understanding which neurotransmitters and brain regions are involved in sleep2, and how the timings of sleep and wakefulness are controlled by an internal (circadian) clock3, among other things. Yet we still do not have answers to the most basic questions. It is not really understood, for instance, what sleep is for, how much is optimal, how sleep quality can be measured and predicted, or the role of genetic and environmental factors in determining ideal sleeping patterns. One reason for this lack of understanding is that most of what is known about sleep comes from laboratory studies. Subjects in these studies tend to be mice or hamsters that are kept in artificial light–dark cycles, or people who have been instructed to sleep at certain times in beds that are not their own, with electrodes fastened to their heads. Assessments of sleep are also often based on subjective responses to questions about how 'well' people feel after they have slept, or whether they think they experienced a good night's sleep. To learn about sleep in the real world, and to establish how to manage sleep to improve productivity, health and quality of life, we need a multidisciplinary 'human sleep project'. © 2013 Nature Publishing Group
By Susan Milius After 17 years underground, throngs of ruby-eyed cicadas clawed up through the soil this year to partake in a once-in-a-lifetime, synchronized mating frenzy. Except it wasn’t one big insect orgy: It was three. The insects that unearthed themselves to breed in 2013 belong to three distinct species. You need only flip them over to see some differences, written in the varieties of their orange markings. You can hear the differences too, says Chris Simon of the University of Connecticut in Storrs. The tymbals on either side of a male’s abdomen vibrate to make the racket for which cicadas are famous. A chorus of courting Magicicada cassini males sounds like an electric carving knife revving up. M. septendecula coughs out a series of rasps. And M. septendecim serenades with the whistling drone of a B-movie spaceship. The various thrums and buzzings may mingle in the same neighborhood, but the last time ancestors of these species mated with each other was almost 4 million years ago, Simon says. That’s the conclusion of the most detailed genetic studies yet of periodical cicada evolutionary history, which Simon and colleagues published in April in the Proceedings of the National Academy of Sciences. With DNA plus episodic field observations, the scientists are getting an idea about the odd family tree of periodical cicadas, how the insects synchronize their life cycles and why they breed side-by-side with others unsuitable for mating. © Society for Science & the Public 2000 - 2013
By DAVID DOBBS On average, about 700 Americans kill themselves each week — but in the fine-weather weeks of May and June, the toll rises closer to 800, sometimes higher. Every year, suicide peaks with the tulips and lilacs — increasing roughly 15 percent over the annual average to create one of psychiatry’s most consistent epidemiological patterns. It may seem perverse that the period of spring and early summer, as the psychologist Kay Redfield Jamison puts it in her splendid book “Night Falls Fast,” should contain “a capacity for self-murder that winter less often has.” Yet it does. This grim spring growth confounds conventional belief that suicides peak in winter. It also confounds researchers — and fascinates them. As they discover more angles into the biology of mood and behavior, they are finding new clues about why suicides rise with the sun’s arc. They hope solving this puzzle will help us better understand why people commit suicide at all — and perhaps reduce the numbers year-round. This effort takes an extra urgency from what Dr. Adam Kaplin, a psychiatrist at Johns Hopkins University, calls a “suicide epidemic” — a sharp increase in both absolute and per-capita rates since the recession that began in 2007, particularly among the middle-aged. More than 38,000 people committed suicide in the United States in 2010 — a 16.5 percent jump from the 32,600 suicides five years before, and a new high. The stakes involved in figuring out the dynamics of self-murder seem only to rise with time. The spring surge in suicides is actually the largest of a few oscillations throughout the year. After dropping to an annual low in February (October in the southern hemisphere), rates climb sharply through spring; fall slowly in summer; show a slight rise, according to some studies, in fall; and then begin a steep winter drop. The spring peak generally runs 10 to 25 percent above the yearly average and 20 to 50 percent above the February low. Copyright 2013 The New York Times Company
by Sue Langthorp Losing sleep doesn't just make us hazy and irritable. It can also lead to cardiovascular disease, type 2 diabetes, and a host of other conditions. But catching up on some shuteye may help combat these problems. According to a new study, sleep-deprived men who dozed an extra 2 to 3 hours on the weekend may reduce their risk of developing type 2 diabetes. Researchers led by Peter Liu, an endocrinologist at the Los Angeles Biomedical Research Institute at the Harbor-University of California, Los Angeles, Medical Center, recruited 19 men in good health who, due to their workload, were poor sleepers. The subjects, age 29 on average, had been clocking about 6 hours of shuteye on weeknights for just over 5 years. However, they made the most of their weekends and slept an extra 2.3 hours a night on Friday and Saturday. When selecting the candidates for the trial, the scientists verified their reported schedules using sleep actigraphs, devices worn like wrist watches that record sleep patterns. The men slept in the lab for three nights. Some were allowed to sleep 10 hours without interruption, catching up on the sleep that they had lost earlier in the week. Others slept 10 hours with frequent interruption, and still others slept 6 hours without interruption. All the subjects ate the same diet, so the researchers could normalize their insulin and sugar levels. © 2010 American Association for the Advancement of Science
By JANE E. BRODY Think you do just fine on five or six hours of shut-eye? Chances are, you are among the many millions who unwittingly shortchange themselves on sleep. Research shows that most people require seven or eight hours of sleep to function optimally. Failing to get enough sleep night after night can compromise your health and may even shorten your life. From infancy to old age, the effects of inadequate sleep can profoundly affect memory, learning, creativity, productivity and emotional stability, as well as your physical health. According to sleep specialists at the University of Pittsburgh School of Medicine and Western Psychiatric Institute and Clinic, among others, a number of bodily systems are negatively affected by inadequate sleep: the heart, lungs and kidneys; appetite, metabolism and weight control; immune function and disease resistance; sensitivity to pain; reaction time; mood; and brain function. Poor sleep is also a risk factor for depression and substance abuse, especially among people with post-traumatic stress disorder, according to Anne Germain, associate professor of psychiatry at the University of Pittsburgh. People with PTSD tend to relive their trauma when they try to sleep, which keeps their brains in a heightened state of alertness. Dr. Germain is studying what happens in the brains of sleeping veterans with PTSD in hopes of developing more effective treatments for them and for people with lesser degrees of stress that interfere with a good night’s sleep. Copyright 2013 The New York Times Company
Link ID: 18280 - Posted: 06.17.2013
Matt Kaplan Just as city slickers have faster-paced lives than country folk, so too do urban birds, compared with their forest-dwelling cousins. The reason, researchers report today, is that urban noise and light have altered the city birds’ biological clocks1. The finding helps to explain prior reports that urban songbirds adopt more nocturnal lifestyles2–4 — data that prompted Davide Dominoni, an ecologist at the Max Planck Institute for Ornithology in Radolfzell, Germany, to investigate whether the birds’ activity patterns were merely behavioural responses to busy cities or were caused by an actual shift in the animals' body clocks. For the study, published in Proceedings of the Royal Society B, Dominoni and his colleagues set up an experiment with European blackbirds (Turdus merula). The scientists attached tiny 2.2-gram radio-pulse transmitters to blackbirds living in Munich, Germany, as well as to those living in a nearby forest. The transmitters monitored the birds’ activity for three weeks. Dominoni found that whereas forest birds started their activity at dawn, city birds began 29 minutes earlier, on average, and remained active for 6 minutes longer in the evening. Keen to determine these differences were due to physiological changes, Dominoni collected blackbirds from both locations and placed them into light- and sound-proof enclosures. For ten days these enclosures were illuminated with a constant, dim light so the birds had no idea what time of day it was, and their activity patterns were monitored. © 2013 Nature Publishing Group,
Keyword: Biological Rhythms
Link ID: 18233 - Posted: 06.05.2013
Posted by Dr. Claire McCarthy Thumbnail image for sleep.jpgAccording to a study just released, the number of hours kids sleep at night is more affected by genetics than by bedtime or how quiet or dark it is. While daytime naps can be affected and changed by messing with the environment, nighttime sleep is a more wired thing. This doesn’t surprise me at all, actually. For years I’ve been hearing from parents about how much their children sleep, and there is remarkable variation. Some kids sleep a lot at night and a lot during the day too, while others truly barely sleep at all—and yet, for the most part, they seem to get the sleep they need. It’s hard to explain this variation to parents, who understandably think that all kids of a certain age must need roughly the same amount of sleep. That’s just one of the conversations I seem to have again and again about sleep. When I read the study I thought: this would be a great opportunity to write a blog about the things I wish all parents knew about sleep. So here they are: Every child needs a different amount of sleep, as the study points out. It depends on age, to some extent, but it also depends on genetics, what they do during the day and all sorts of factors we don’t understand yet. So instead of counting hours, look at your kid. Are they generally tired or cranky during the day? If so, they may need more sleep. If they are healthy, act rested, have enough energy, get along with others (and are doing okay in school if they go to school), they are probably getting enough sleep. © 2013 NY Times Co.
Link ID: 18216 - Posted: 06.01.2013
How long a toddler sleeps at night depends in part on genes but environmental factors seem to make more of a difference for naps, a study of nearly 1,000 Canadian twins suggests. Researchers asked parents of 405 identical and 586 fraternal infants born in the Montreal area to answer questions about daytime and nighttime sleep habits at ages six months, 18 months, 30 months and 48 months. Twin girls sleep. Canadian researchers studied the sleep habits of twins, with the results being published this week.Twin girls sleep. Canadian researchers studied the sleep habits of twins, with the results being published this week. (iStock) "This study is the first to show that daytime sleep duration in early childhood is strongly influenced by environmental factors," Dr. Jacques Montplaisir from the University of Montreal and his colleagues concluded in Monday's issue of the journal Pediatrics. At most ages, genetics accounted for between 47 and 58 per cent of nighttime sleep duration. The majority of children slept 10 or 11 continuous hours at night. The exception was nighttime sleep at 18 months, which the researchers called "a critical environmental time-window" for establishing sleep patterns. On the other hand, genes never explained more than about one-third of daytime nap time. Environmental factors like family routines accounted for between 33 and 79 per cent of whether or not twins napped and for how long. © CBC 2013
By Michelle Roberts Health editor, BBC News online Sharing a bed with a newborn increases the risk of sudden infant death syndrome fivefold, research claims. The risk applies even if parents avoid tobacco, alcohol and drugs - other factors firmly linked to cot deaths. The BMJ Open research compared nearly 1,500 cot deaths with a control group of more than 4,500 parents. Current guidance in the UK is that parents should decide where their baby sleeps, but says the safest option is in a crib or cot in the same room. No consensus Many other countries, such as the US and the Netherlands, go further and say parents should not share a bed with their baby for the first three months of his or her life. Prof Bob Carpenter, from the London School of Hygiene & Tropical Medicine, carried out the analysis and says the UK should now follow suit and "take a more definitive stance against bed-sharing for babies under three months". The government said it had asked the public health watchdog NICE to urgently examine its guidance on co-sleeping in light of this new study. BBC © 2013
Link ID: 18179 - Posted: 05.21.2013
20:00 13 May 2013 by Douglas Heaven Genes in cells throughout the body switch on and off throughout the day in a coordinated way. Or at least they should. In people with clinical depression, genes in their brain tissues appear to be significantly out of sync – a finding that could lead to new treatments for the condition. We know from previous studies that genes in cells elsewhere, such as the skin, follow a 24-hour cycle of activity. But identifying patterns of genetic activity in a living brain isn't easy to do. "We always assumed we would have a clock [in our brain]," says Huda Akil at the University of Michigan in Ann Arbor. "But it had never been shown before." Akil and her colleagues examined the brains of 55 people with a known time of death, looking at around 12,000 genes in tissues from six brain regions. By matching the time of death with molecular signs of genetic activity – whether each gene was actively expressing itself or not – the team identified hundreds of genes that follow a daily cycle. Sudden death Akil says it was important to look at the brains of individuals who had died suddenly – through a heart attack or car accident, for example. Slower deaths can cause dramatic changes in the brain that would have obscured what they were looking for, but sudden death freezes the genetic activity. "We can capture an instant," she says. © Copyright Reed Business Information Ltd.
By Samyukta Mullangi A recent article in NYTimes  declared that the rising rate of suicides among our baby boomer generation now made suicides, by raw numbers alone, a bigger killer than motor vehicle accidents! Researchers quoted within the article pointed to complex reasons like the economic downturn over the past decade, the widespread availability of opioid drugs like oxycodone, and changes in marriage, social isolation and family roles. Then I scrolled down, as I always do, to peruse some of the readers’ comments, and that’s when I paused. I suppose in hindsight that I had expected readers to exclaim at the shocking statistics (suicide rates now stand at 27.3 per 100,000 for middle aged men, 8.1 per 100,000 for women), or lament over personal stories of relatives or friends who took their own lives. While I certainly saw a few such comments, I was amazed to discover the number of readers who were sympathetic to the idea of suicide. “Molly” wrote “Why is suicide usually looked upon as a desperate and forbidden act? Can’t we accept that in addition to poverty, loneliness, alienation, ill health, life in world [sic] that is sometimes personally pointless means that death is a relief? I believe the right to die, in a time and place (and wishfully peacefully without violence) is a basic human right.” This post was ‘recommended’ by 351 other readers at the time of this essay being written. © 2013 Scientific American
By VATSAL G. THAKKAR IN the spring of 2010, a new patient came to see me to find out if he had attention-deficit hyperactivity disorder. He had all the classic symptoms: procrastination, forgetfulness, a propensity to lose things and, of course, the inability to pay attention consistently. But one thing was unusual. His symptoms had started only two years earlier, when he was 31. Though I treat a lot of adults for attention-deficit hyperactivity disorder, the presentation of this case was a violation of an important diagnostic criterion: symptoms must date back to childhood. It turned out he first started having these problems the month he began his most recent job, one that required him to rise at 5 a.m., despite the fact that he was a night owl. The patient didn’t have A.D.H.D., I realized, but a chronic sleep deficit. I suggested some techniques to help him fall asleep at night, like relaxing for 90 minutes before getting in bed at 10 p.m. If necessary, he could take a small amount of melatonin. When he returned to see me two weeks later, his symptoms were almost gone. I suggested he call if they recurred. I never heard from him again. Many theories are thrown around to explain the rise in the diagnosis and treatment of A.D.H.D. in children and adults. According to the Centers for Disease Control and Prevention, 11 percent of school-age children have now received a diagnosis of the condition. I don’t doubt that many people do, in fact, have A.D.H.D.; I regularly diagnose and treat it in adults. But what if a substantial proportion of cases are really sleep disorders in disguise? © 2013 The New York Times Company
By Russell Foster "Making teens start school in the morning is ‘cruel,’ brain doctor claims." So declared a British newspaper headline in 2007 after a talk I gave at an academic conference. One disbelieving reader responded: "This man sounds brain-dead." That was a typical reaction to work I was reporting at the time on teenage sleep patterns and their effect on performance at school. Six years on, there is growing acceptance that the structure of the academic day needs to take account of adolescent sleep patterns. The latest school to adopt a later start time is the UCL Academy in London; others are considering following suit. So what are the facts about teenage slumber, and how should society adjust to these needs? The biology of human sleep timing, like that of other mammals, changes as we age. This has been shown in many studies. As puberty begins, bedtimes and waking times get later. This trend continues until 19.5 years in women and 21 in men. Then it reverses. At 55 we wake at about the time we woke prior to puberty. On average this is two hours earlier than adolescents. This means that for a teenager, a 7 a.m. alarm call is the equivalent of a 5 a.m. start for people in their 50s. Precisely why this is so is unclear, but the shifts correlate with hormonal changes at puberty and the decline in those hormones as we age. However, biology is only part of the problem. Additional factors include a more relaxed attitude to bedtimes by parents, a general disregard for the importance of sleep, and access to TVs, DVDs, PCs, gaming devices, cellphones, and so on, all of which promote alertness and eat into time available for sleep. © 2013 The Slate Group, LLC.
By David Levine Sleep deprivation is a quick and efficient way to treat depression. It works 60 to 70 percent of the time—far better than existing drugs—but the mood boost usually lasts only until the patient falls asleep. As an ongoing treatment, sleep deprivation is impractical, but researchers have been studying the phenomenon in an effort to uncover the cellular mechanisms behind depression and remission. Now a team at Tufts University has pinpointed glia as the key players. The researchers previously found that astrocytes, a star-shaped type of glial cell, regulate the brain chemicals involved in sleepiness. During our waking hours, astrocytes continuously release the neurotransmitter adenosine, which builds up in the brain and causes “sleep pressure,” the feeling of sleepiness and its related memory and attention impairments. The neurotransmitter causes this pressure by binding to adenosine receptors on the outside of neurons like a key fitting into a lock. As more adenosine builds up, more receptors are triggered, and the urge to sleep gets stronger. In the new study, published online January 15 in the journal Translational Psychiatry, the scientists investigated whether this process is responsible for the antidepressant effects of sleep deprivation. Mice with depressivelike symptoms were administered three doses of a compound that triggers adenosine receptors, thus mimicking sleep deprivation. Although the mice continued to sleep normally, after 12 hours they showed a rapid improvement in mood and behavior, which lasted for 48 hours. © 2013 Scientific American
Published by scicurious under Behavioral Neuro It's late. I've got a lot on my plate. A lot to do. And most of us do. So here I am, burning the midnight oil along with many of my neighbors. I usually count myself lucky to get 7 hours a night, and I AM lucky. For many parents or other caregivers, for example, 7 hours is unheard-of luxury. Is it just me? Probably not. Most of us don't get enough sleep, and those who don't sleep? Snack. But why? And what does this mean for issues like obesity? We know that there has been an increase in obesity in this country. And many people are asking why. There are probably lots of reasons involved: too much sugar, too little exercise, genetics, too much fat. But what about sleep? It turns out that getting less sleep is a risk factor for obesity, but...how are sleep and weight gain related? It turns out that sleep, or lack thereof, can have a lot of influence on how much we need to eat and how much we feel like eating. For example, sleep deprivation changes hunger hormone levels, which can change food intake, and some scientists hypothesize that decreased sleep can change energy expenditure as well. But in order to understand just how lack of sleep influences weight gain, well you need to sleep deprive some people. The authors took 8 men and 8 women who reported getting an average of 8 hours of sleep per night into an inpatient facility. They were taken off caffeine one week before the study and were told to stick to 9 hours of sleep opportunity (stay in bed 9 hours) per night for the first week. They also were put on a diet that was calibrated exactly to maintain their current weight. Copyright © 2013