Links for Keyword: Biological Rhythms

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The brain function of very late risers and "morning larks" during the hours of the working day is different, according to a study. Researchers scanned the brains of night owls with a bedtime of 02:30 and a wake time of 10:15, along with early risers. The tests - performed between 08:00 and 20:00 - found night owls had less connectivity in brain regions linked to maintaining consciousness. They also had poorer attention, slower reactions and increased sleepiness. Researchers said it suggested that night owls were disadvantaged by the "constraints" of the typical working day. They called for more research to understand the health implications of night owls performing on a work or school schedule to which they are not naturally suited. Scientists took 38 people who were either night owls or morning larks (people who went to bed just before 23:00 and woke at 06:30) and investigated their brain function at rest using magnetic resonance imaging (MRI) scans. The volunteers then carried out a series of tasks at various times, from 08:00 to 20:00, and were asked to report on their levels of sleepiness. Morning larks were least sleepy and had their fastest reaction time in the early morning tests. They were also found to perform significantly better at this time than night owls. In contrast, night owls were least sleepy and had their fastest reaction time at 20:00, although they did not do significantly better than the larks at this time. The brain connectivity in the regions that predicted better performance and lower sleepiness was significantly higher in larks at all time points, suggesting connectivity in late risers is impaired throughout the whole working day, researchers said. © 2019 BBC

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25967 - Posted: 02.15.2019

By Ronnie Cohen At first, Lilly Grey Rudge objected to her classes starting later. Delaying the first-period bell nearly an hour until 8:45 a.m. meant that her mother could no longer drive her, and Lilly Grey would have to take two buses to Ballard High in Seattle. Now, more than two years since the change, the 16-year-old junior is a fan. “I’ve gained an hour of sleep,” she said. “I definitely feel a lot better. I find myself waking up around 7:30 without an alarm because it’s a natural time. It’s a great, great feeling.” Other Seattle high school students also are sleeping more — a median of 34 minutes a night more — since the school district pushed back the start of classes from 7:50 a.m. to 8:45 a.m. in fall 2016, a new study shows. Plus, when school began later, grades and attendance went up, and tardiness went down. After Franklin High in Seattle reset its starting bell, teacher A.J. Katzaroff’s first-period biology students’ median grades rose from a C to a B. “Kids were more awake, more present and more capable of engaging in intellectual work because they had the rest they needed,” she said. Cindy Jatul, a biology teacher at Seattle’s Roosevelt High, also saw the benefits of the later start time on her students. “Prior to the change, my first-period class would just make silly mistakes because they weren’t firing on all cylinders,” she said. “They were in this kind of fog. There were kids who were sleeping in class, their heads on the table.” © 1996-2019 The Washington Post

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25948 - Posted: 02.11.2019

Jef Akst Whether you’re an early bird or a night owl is partly dependent on your genome, according to a study published this week (January 29) in Nature Communications. Scanning nearly 700,000 human genomes available through the UK Biobank and the consumer genetics testing company 23andMe and comparing the results with reported sleep preferences, an international team of researchers identified more than 350 variations associated with being a morning person. Additional analyses using the device-recorded activity patterns of more than 85,000 of these participants revealed that people who carried the most gene variants linked with being an early bird went to bed an average of 25 minutes earlier than those who carried the fewest. The team went on to study the potential roles of these gene variants, and found that many had functions in regulating circadian rhythms. Some were active in the brain, while others were active in the retina. One of the genes participates in the body’s responses to caffeine and nicotine. But, coauthor Michael Weedon, a bioinformaticist at the University of Exeter in the UK, tells The New York Times, “the most interesting ones are the ones where we don’t know what it is.” The researchers found links between people’s sleep preferences, or chronotypes, and their mental health, with those who identified as morning people being less likely to report having depression or schizophrenia and reporting higher levels of general well-being. But chronotype is not a simple variable, Suzanne Hood, an assistant professor of psychology at Bishop’s University in Quebec who was not involved in the study, tells CNN, and future studies should take the nuance of the phenotype into account. “It would be interesting to follow up these findings with other kinds of methods that can track sleep variables with more precision.” © 1986 - 2019 The Scientist.

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25926 - Posted: 02.02.2019

By Emily Laber-Warren A few years ago, scientists conducted a real-world experiment at a ThyssenKrupp steel factory in Germany. They assigned the day shift to early risers and the late shift to night owls. Soon the steel workers, many of whom had been skeptical at the outset, were getting an extra hour of sleep on work nights. By simply aligning work schedules with people’s internal clocks, the researchers had helped people get more and better rest. “They got 16 percent more sleep, almost a full night’s length over the course of the week,” said Till Roenneberg, a chronobiologist at Ludwig-Maximilian University in Munich, who headed the study. “That is enormous.” In recent years, American educators have been paying increased attention to their students’ sleep needs, with growing debate about delaying school start times. Now a number of businesses are following suit, encouraging their employees to work when their bodies are most awake. “It’s a huge financial burden not to sleep properly,” Dr. Roenneberg said. “The estimates go toward 1 percent of gross national product,” both in the United States and Germany. Emerging science reveals that each of us has an optimal time to fall asleep and wake up, a personalized biological rhythm known as a “chronotype.” When you don’t sleep at the time your body wants to sleep — your so-called biological night — you don’t sleep as well or as long, setting the stage not only for fatigue, poor work performance and errors but also health problems ranging from heart disease and obesity to anxiety and depression. A full 80 percent of people have work schedules that clash with their internal clocks, said Céline Vetter, an assistant professor at the University of Colorado at Boulder and director of the university’s circadian and sleep epidemiology lab. “The problem is huge,” Dr. Vetter said. “If we consider your individual chronotype and your work hours, the chances are very high that there’s quite a bit of misalignment.” © 2018 The New York Times Company

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 18: Attention and Higher Cognition
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 14: Attention and Consciousness
Link ID: 25822 - Posted: 12.26.2018

Micaela Martinez, Kevin M. Bakker Does it ever seem like you’re invited to an awful lot of summer birthday gatherings? For good reason. In the United States, most births occur between June and early November. Count back nine months, and you’ll see that places most conceptions in the fall and winter. What’s going on? Is the crisp autumn air, or the joy (or anxiety) of the holiday season, triggering more unprotected sexual intercourse? Or is it something else entirely? It turns out reproduction is seasonal across all living organisms, from plants, to insects, to reptiles, to birds and mammals – including human beings. The ultimate explanation for this phenomenon is an evolutionary one. Earth’s environment is seasonal. Above or below the equator, the year is structured by the winter, spring, summer and fall. In equatorial regions, the wet and dry seasons punctuate the year. Organisms have evolved strategies to reproduce at the time of year that will maximize their lifetime reproductive success. Humans are no exception and maintain this evolutionary outcome: birth seasonality. Researchers, including us, have recently been working to understand more about why births are seasonal because these patterns can have a big impact on childhood disease outbreaks. The first studies demonstrating human birth seasonality date back to the early 1800s. © 2010–2018, The Conversation US, Inc.

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 13: Memory, Learning, and Development
Link ID: 25813 - Posted: 12.22.2018

Tina Hesman Saey Timing is everything. Even how many calories a person burns while at rest depends on the hour. People burn about 129 more calories when resting in the afternoon and evening than in the early morning. But morning is better for burning carbohydrates, while fats are more likely to be burned in the evening, researchers report November 8 in Current Biology. The findings add to evidence that when people eat and sleep may be as important as what they eat for maintaining proper health (SN: 10/31/15, p. 10). Calories burned at rest fuel breathing, circulation and brain activity, while also helping to maintain body temperature. Researchers previously had conflicting evidence about whether a resting body burns calories at a fairly constant rate, or one that rises and falls in a daily — or circadian — rhythm. The study shows that a body’s resting metabolism is governed by circadian clocks, neuroscientist Jeanne Duffy of Brigham and Women’s Hospital in Boston and colleagues report. The study followed seven people kept in windowless rooms for three weeks, without any clues to the time of day. Each night, the seven went to bed four hours later than the previous night. That’s the equivalent of traveling around the world and crossing all time zones within a week. The schedule change allowed the researchers to study the natural body rhythms of each subject without outside influences. |© Society for Science & the Public 2000 - 2018.

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 25658 - Posted: 11.09.2018

By James Gallagher Health and science correspondent, BBC News Women whose body clocks mean they are "morning people" have a lower risk of developing breast cancer, say UK researchers. The team at the University of Bristol says the reason why still needs to be uncovered. It adds the findings are important as they may affect every woman's risk. Experts said the study presented at the NCRI Cancer Conference in Glasgow added to a growing understanding of the importance of sleep in all health. Body clock Everybody has a body clock, which governs how the body works in a roughly 24-hour pattern. It's also known as a circadian rhythm. It affects everything from when we sleep, to our mood and even our risk of a heart attack. But not everybody's clock tells the same time. Morning people or "larks" are early to rise, peak earlier in the day and are tired earlier in the evening. Evening people or "owls" find it harder to get up in the morning, are productive later into the evening and prefer to go to sleep late. Take our quiz to find out whether you are a morning type, or an evening owl. And this is involved in breast cancer? The researchers think so. They used a clever new way of analysing data - called Mendelian randomisation. They looked at 341 snippets of DNA (the instructions for the human body) that control whether we are likely to be a lark or an owl. They used this knowledge to perform an experiment on more than 180,000 women in the UK Biobank project and nearly 230,000 women in the Breast Cancer Association Consortium study. They showed people genetically programmed to be "larks" were less likely to have breast cancer than those programmed to be owls. Because these bits of DNA are set at birth and are not linked to other known causes of cancer, like obesity, it means the researchers are reasonably confident body clocks are involved in cancer. © 2018 BBC

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25652 - Posted: 11.07.2018

Allison Aubrey When it comes to turning back the clocks on our devices, technology has us covered. Our smartphones automatically adjust. But our internal clocks aren't as easy to re-program. And this means that the time shift to save daylight in the fall and again in the spring can influence our health in unexpected ways. "You might not think that a one hour change is a lot," says Fred Turek, who directs the Center for Sleep & Circadian Biology at Northwestern University. "But it turns out that the master clock in our brain is pretty hard-wired, " Turek explains. It's synchronized to the 24 hour light/dark cycle. Daylight is a primary cue to reset the body's clock each day. So, if daylight comes an hour earlier — as it will for many of us this weekend — it throws us off. "The internal clock has to catch up, and it takes a day or two to adjust to the new time," Turek says. Scientists have documented that the shift to daylight saving time in the spring, when we lose an hour of sleep, can increase the risk of heart attacks, strokes and traffic accidents. These studies are a reminder of just how sensitive we are to time and rhythm. Over the last 20 years, scientists have documented that, in addition to the master clock in our brains, every cell in our body has a time-keeping mechanism. These clocks help regulate important functions such as sleep and metabolism. And increasingly, there's evidence that when our habits — such as when we eat and sleep — are out of sync with our internal clocks, it can harm us. © 2018 npr

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25641 - Posted: 11.03.2018

Ian Sample In daylight hours there is so little melatonin in the bloodstream that it is barely detectable. But when the sun goes down, the eyes sense the failing light, and part of the hippocampus signals the pineal gland, a pea-sized lump of tissue near the centre of the brain, to ramp up production of the sleep-promoting hormone. Levels of melatonin rise sharply from 9pm, inducing feelings of sleepiness, and remain high until the following morning. Much of the research on prescribing melatonin for children with sleep problems has focused on those with disorders such as autism, ADHD and intellectual disability (ID). For good reason too: sleeping difficulties are far more common and pronounced in children with neurodevelopmental or psychiatric disorders. For them, small doses of melatonin can be safe and effective. In one recent study, researchers from Southampton University monitored the sleep patterns of 45 children with autism, ADHD, or ID, and found that a third fell asleep faster, slept longer, and woke less frequently at night on low dose (2.5-3mg) melatonin. Above 6mg per night there was little extra benefit. A poor night’s sleep can be caused by any number of factors, but there is good evidence that screen time matters, whether it is TV, computer, tablet or mobile phone. A recent review of scientific papers on the issue found that 90% linked screen time to poor sleep in schoolchildren and adolescents. Part of the problem is obvious: being online at bedtime eats into the hours left for sleep, and it hardly helps people to wind down for the night. But glowing screens can affect sleep directly by suppressing the natural production of melatonin. Using an iPad on full brightness for two hours, for example, has been shown to suppress melatonin levels. © 2018 Guardian News and Media Limited

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 5: Hormones and the Brain
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 8: Hormones and Sex
Link ID: 25640 - Posted: 11.03.2018

By Jason Bittel The first mammals first lived some 160 million years ago, in a world ruled by reptiles. And now scientists suggest that hiding in the dark from these terrifying beasts may have left an imprint in mammals’ genes that can still be seen today. Most mammals were no bigger than a squirrel back then, and it would have been much safer to come out only at night, thereby avoiding most of the nastiest maws and claws. A new study published Thursday in Current Biology suggests that living largely in the dark for millions of years might explain how mammals lost a light-sensitive trick that nearly every other living thing possesses. You see, if you were to examine the DNA of a turtle, an orchid, a coral, or even a bacterium, you would find a quirky little set of genes that allows these organisms to repair damage caused by one kind of sunlight with energy absorbed from another kind of sunlight. Think of it like a solar panel that is both harmed and healed by the sun. How is it possible that we lost an evolutionary strategy so advantageous it’s been found in every other living thing where scientists have looked for it? Well, you might blame the dinosaurs—or at least how scary they were. All that time spent in darkness, when most dinosaurs weren’t active, may have affected the way placental mammals evolved. Scientists call this theory the “nocturnal bottleneck,” and it’s supported by various mammalian oddities such as the shape of our eyes, the composition of our retinas, and our heightened senses of smell and hearing—all of which point to a long history of living in the dark.

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 6: Evolution of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25572 - Posted: 10.15.2018

By Henry Nicholls A fresh-faced batch of teenagers just began a new school year, but will they get the most out of it? In the mornings, many are forced to get to school much too early. And at night, ubiquitous screens are a lure that’s hard to resist. This double whammy is a perfect lesson in sleep deprivation. Three out of every four students in grades 9 to 12 fail to sleep the minimum of eight hours that the American Academy of Sleep Medicine recommends for their age group. And sleep deprivation is unremittingly bad news. Anyone who talks about sleep as if it’s some kind of inconvenience and getting less of it is a virtue should be challenged. These people are dangerous. At its most basic, insufficient sleep results in reduced attention and impaired memory, hindering student progress and lowering grades. More alarmingly, sleep deprivation is likely to lead to mood and emotional problems, increasing the risk of mental illness. Chronic sleep deprivation is also a major risk factor for obesity, Type 2 diabetes, hypertension, cardiovascular disease and cancer. As if this weren’t enough, it also makes falling asleep at the wheel much more likely. It is important to understand why teenagers have a particularly hard time getting enough sleep, and what adults need to do to help. First, a reminder of the basic biology: After puberty, adolescents are no longer the morning larks of their younger years. They become rewired as night owls, staying awake later and then sleeping in. This is not part of a feckless project to frustrate parents, but is driven by changes in the way the brain responds to light. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 7: Life-Span Development of the Brain and Behavior
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 13: Memory, Learning, and Development
Link ID: 25484 - Posted: 09.24.2018

Diana Kwon In the early 2000s, Stefano Schiaffino, a muscle physiologist at the University of Padova in Italy, was faced with puzzling results: two seemingly identical experiments involving hind leg muscles in rats had yielded different findings. Schiaffino and his team were investigating nuclear factor of activated T cells (NFAT), a transcription factor that responds to the level of muscle activity. Despite using similar procedures, the researchers found that in the tissues from one set of animals, NFAT had moved from the cytoplasm into the nucleus in a large proportion of cells, while in tissues from another experiment, this change had not occurred. The explanation for this difference turned out to be simple: timing. The researcher responsible for one trial had sacrificed the nocturnal animals in the evening, while another had conducted the same procedure for the second trial in the morning. This meant that the first group of animals was more active at the time of measurement than the second. When the scientists repeated the second experiment late in the day, when the animals were more likely to be awake, they observed high levels of NFAT in the nuclei of the muscle cells, essentially replicating the first experiment. “At that time, I’d been working for many years on muscle, but had never thought about the circadian rhythms,” recalls Schiaffino, whose research now focuses on this aspect of muscle biology. © 1986 - 2018 The Scientist

Related chapters from BN8e: Chapter 13: Homeostasis: Active Regulation of the Internal Environment; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 9: Homeostasis: Active Regulation of the Internal Environment; Chapter 10: Biological Rhythms and Sleep
Link ID: 25432 - Posted: 09.11.2018

/ By Richard G ‘Bugs’ Stevens Light pollution is often characterized as a soft issue in environmentalism. This perception needs to change. Light at night constitutes a massive assault on the ecology of the planet, including us. It also has indirect impacts because, while 20 percent of electricity is used for lighting worldwide, at least 30 percent of that light is wasted. Wasted light serves no purpose at all, and excessive lighting is too often used beyond what is needed for driving, or shopping, or Friday-night football. It might be that virtually all aspects of health and wellbeing are dependent to one extent or another on a synchronized circadian rhythmicity, with a natural cycle of bright days and dark nights. The electric light bulb is touted as one of the most significant technological advancements of human beings. It ranks right up there with the wheel, control of fire, antibiotics, and dynamite. But as with any new and spectacular technology, there are invariably unintended consequences. With electric light has come an obliteration of night in much of the modern world; both outside in the city, and indoors during what was once ‘night’ according to the natural position of the sun. Life has evolved for several billion years with a reliable cycle of bright light from the sun during the day, and darkness at night. This has led to the development of an innate circadian rhythm in our physiology; that circadian rhythm depends on the solar cycle of night and day to maintain its precision. During the night, beginning at about sunset, body temperature drops, metabolism slows, hunger abates, sleepiness increases, and the hormone melatonin rises dramatically in the blood. This natural physiological transition to night is of ancient origin, and melatonin is crucial for the transition to proceed as it should. Copyright 2018 Undark

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25345 - Posted: 08.17.2018

By Anahad O’Connor Nutrition scientists have long debated the best diet for optimal health. But now some experts believe that it’s not just what we eat that’s critical for good health, but when we eat it. A growing body of research suggests that our bodies function optimally when we align our eating patterns with our circadian rhythms, the innate 24-hour cycles that tell our bodies when to wake up, when to eat and when to fall asleep. Studies show that chronically disrupting this rhythm — by eating late meals or nibbling on midnight snacks, for example — could be a recipe for weight gain and metabolic trouble. That is the premise of a new book, “The Circadian Code,” by Satchin Panda, a professor at the Salk Institute and an expert on circadian rhythms research. Dr. Panda argues that people improve their metabolic health when they eat their meals in a daily 8- to 10-hour window, taking their first bite of food in the morning and their last bite early in the evening. This approach, known as early time-restricted feeding, stems from the idea that human metabolism follows a daily rhythm, with our hormones, enzymes and digestive systems primed for food intake in the morning and afternoon. Many people, however, snack and graze from roughly the time they wake up until shortly before they go to bed. Dr. Panda has found in his research that the average person eats over a 15-hour or longer period each day, starting with something like milk and coffee shortly after rising and ending with a glass of wine, a late night meal or a handful of chips, nuts or some other snack shortly before bed. That pattern of eating, he says, conflicts with our biological rhythms. Scientists have long known that the human body has a master clock in the brain, located in the hypothalamus, that governs our sleep-wake cycles in response to bright light exposure. A couple of decades ago, researchers discovered that there is not just one clock in the body but a collection of them. Every organ has an internal clock that governs its daily cycle of activity. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 25246 - Posted: 07.25.2018

By Dana G. Smith Suicide rates and temperatures are both on the rise, but are these two occurrences connected? A new study suggests maybe so. The research revealed hotter-than-average months corresponded to more deaths by suicide—and the effect isn’t limited to the summer, even warmer winters show the trend. In the study, published in Nature Climate Change, the investigators looked at all of the suicides that occurred in the U.S. and Mexico over several decades (1968 to 2004 for the U.S. and 1990 to 2010 for Mexico), comprising 851,088 and 611,366 deaths, respectively. They then observed how monthly temperature fluctuations over these periods in every county or municipality in both countries correlated to the suicide rates for that region. They discovered that for every 1-degree Celsius (1.8-degree Fahrenheit) rise in temperature, there was a 0.7 percent increase in suicide rates in the U.S. and a 2.1 percent increase in Mexico, averaging a 1.4 percent increment across both countries. That is, over the years, a given county would see more deaths by suicide in warmer-than-average months. Notably, the average temperature of the county did not matter; for example, Dallas and Minneapolis saw a similar rise in suicide rates. The effect did not depend on the month either—it made no difference whether it was January or July. There was also no difference between gender, socioeconomic status, access to guns, air-conditioning and whether it was an urban or rural region. Across the board, when temperatures rose in a given place, so did the number of suicides. © 2018 Scientific American

Related chapters from BN8e: Chapter 16: Psychopathology: Biological Basis of Behavior Disorders; Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 12: Psychopathology: The Biology of Behavioral Disorders; Chapter 10: Biological Rhythms and Sleep
Link ID: 25243 - Posted: 07.24.2018

by Caroline Wellbery Jet lag can put the brakes on the most exciting vacations. Almost everyone who has ever flown across time zones knows what it feels like. The experience ranks somewhere between eating day-old cooked oatmeal and nursing a hangover. These food and drink metaphors aren’t just a coincidence. Jet lag, it turns out, affects more than our sleep; it affects our internal organs as well. Given what is known about the importance of intestinal bacteria (called the microbiome) and their connection to immune function and well-being, it’s clear that any discussion of jet lag, and how to deal with it, needs to consider “gut lag”as well. The issues begin with the fact that air travel across time zones disrupts our circadian rhythm — the human internal clock that evolved over millennia to match Earth’s 24-hour cycle of light and dark. One feature of this cycle is that maximum sleepiness coincides with a low point in core body temperature, which is usually unrelated to external temperatures. Core body temperature goes down as you sleep and is usually lowest two to three hours before waking (which also coincides with your deepest sleep). Low core body temperature appears to be a turning point in determining how sleepy or rested you feel, depending on when in the cycle you wake up. When you fly into a new time zone, your core body temperature doesn’t recognize that change and instead continues to dip according to the schedule of the place you have left. If you are awake or wake up before the dip, you are much more likely to feel groggy or out of sorts, especially if you are exposed to light while your body temperature drops. That’s because light and temperature signals come into conflict with each other: The light tells you that you’re wide-awake; the temperature signal tells you that you’re about to enter the deepest point in your sleep. This is when you will mostly strongly feel the unpleasant symptoms of jet lag. © 1996-2018 The Washington Post

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25236 - Posted: 07.23.2018

Layal Liverpool Working night shifts can mess up the body’s natural rhythms so much that the brain and digestive system end up completely out of kilter with one another, scientists say. Three night shifts in a row had little impact on the body’s master clock in the brain, researchers found, but it played havoc with gut function, throwing the natural cycle out by a full 12 hours. The finding highlights the dramatic impact that night shifts can have on the different clocks that govern the natural rhythms of organs and systems throughout the human body. Internal disagreements over night and day may explain why people on night shifts, and those with jet lag, can suffer stomach pains and other gut problems, which clear up once their body has had time to adjust. “One of the first symptoms people experience when traveling across time zones is gastrointestinal discomfort and that’s because you knock their gut out of sync from their central biological clock,” said Hans Van Dongen, director of the Sleep and Performance Research Center at Washington State University. For the study, Van Dongen invited 14 healthy volunteers aged 22 to 34 into his sleep lab and split them into two groups. The first spent three days on a simulated day shift and could sleep from 10pm to 6am each night. Those in the second group stayed awake for three nights in a row and were only allowed to sleep from 10am to 6pm. © 2018 Guardian News and Media Limited

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 13: Homeostasis: Active Regulation of the Internal Environment
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 9: Homeostasis: Active Regulation of the Internal Environment
Link ID: 25188 - Posted: 07.10.2018

By Sean Coughlan BBC News education and family correspondent The colour cyan - between green and blue - is a hidden factor in encouraging or preventing sleep, according to biologists. University of Manchester researchers say higher levels of cyan keep people awake, while reducing cyan is associated with helping sleep. The impact was felt even if colour changes were not visible to the eye. The researchers want to produce devices for computer screens and phones that could increase or decrease cyan levels. Sleep researchers have already established links between colours and sleep - with blue light having been identified as more likely to delay sleep. There have been "night mode" settings for phones and laptops which have reduced blue light in an attempt to lessen the damage to sleep. But the research by biologists at the University of Manchester and in Basel in Switzerland, published in the journal Sleep, has shown the particular impact of the colour cyan. When people were exposed to more or less cyan, researchers were able to measure different levels of the sleep hormone melatonin in people's saliva. Prof Rob Lucas said that it was not necessary for someone to be able to see the difference in colours, as the body reacted to the change even if it was not visible to the naked eye. He said this could also affect other colours which were made using cyan. For instance, there are shades of green that can include cyan - which also can be achieved using other colour combinations. The researchers suggest that versions of the colour using cyan could be used on computer screens if the aim was to keep people awake - such as people working and required to stay alert at night. © 2018 BBC.

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 10: Vision: From Eye to Brain
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 7: Vision: From Eye to Brain
Link ID: 25120 - Posted: 06.22.2018

By Nicholas Bakalar Night owls may be at greater risk for depression than early birds. Previous studies have found a link between a person’s unique circadian rhythm, or chronotype, and depression, but none were able to tell whether sleep habits were a cause or an effect of the disease. This new prospective study, in the Journal of Psychiatric Research, is a step closer to establishing causality. Researchers gathered health and behavioral data on 32,740 women whose average age was 55. Each categorized herself as a definite evening or morning type, a somewhat morning or evening type, or neither. All were free of depression at the start of the study, and over the following four years 2,581 of them developed depression, defined by antidepressant use or a clinical diagnosis. After adjusting for marital status, living alone, being retired, alcohol consumption and other variables, the researchers found that compared to the intermediate types, morning people were 12 percent less likely to develop depression, and night owls 6 percent more likely to develop it. The relationship was linear: the more a woman tended toward the night-owl type, the more likely she was to develop depression. “The effect is modest, a modest association for chronotype and incident depression,” said the lead author, Céline Vetter, an assistant professor at the University of Colorado. “But the overall pattern remains constant. We need to get much deeper into what the genetic and environmental contributions are between mood and chronotype.” © 2018 The New York Times Company

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming; Chapter 16: Psychopathology: Biological Basis of Behavior Disorders
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep; Chapter 12: Psychopathology: The Biology of Behavioral Disorders
Link ID: 25113 - Posted: 06.21.2018

By Julia Jacobs Humans, it turns out, can annoy more than just one another. In fact, some animal populations are escaping their Homo sapien cohabitants by sleeping more during the day, a new study finds. Mammals across the globe are becoming increasingly nocturnal to avoid humans’ expanding presence, according to the study, published Thursday in Science magazine. The findings show that humans’ presence alone can cause animals across continents — including coyotes, elephants and tigers — to alter their sleep schedules. “We’re just beginning to scratch the surface on how these behavioral changes are affecting entire ecosystems,” said Kaitlyn Gaynor, an ecologist and graduate student in environmental science at the University of California, Berkeley, who led the study. Previous research has found that mammals went from being noctural to being active during both day and night about 65.8 million years ago, roughly 200,000 years after most dinosaurs went extinct. “Species for millions of years have been adapting to diurnal activity, but now we’re driving them back into the night and may be driving natural selection,” Ms. Gaynor said in an interview. The researchers compiled data from 76 studies of 62 species living on six continents in reaching their conclusions. On average, human disruption is making these animals 1.36 times more nocturnal, according to the study. “For example,” it says, “an animal that typically split its activity evenly between the day and night would increase its proportion of nocturnal activity to 68 percent of total activity near human disturbance.” In California’s Santa Cruz mountains, for example, coyotes are opting to sleep more during the day in response to recreational human activities such as hiking and bicycling. As a result, coyotes are eating more nocturnal prey, whose waking hours match up more closely with theirs. Recent research such as this was used to provide data for the new study, Ms. Gaynor said. © 2018 The New York Times Company

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 25093 - Posted: 06.15.2018