Links for Keyword: Biological Rhythms

Follow us on Facebook and Twitter, or subscribe to our mailing list, to receive news updates. Learn more.


Links 1 - 20 of 310

Patti Neighmond Many American teenagers try to put in a full day of school, homework, after-school activities, sports and college prep on too little sleep. As evidence grows that chronic sleep deprivation puts teens at risk for physical and mental health problems, there is increasing pressure on school districts around the country to consider a later start time. In Seattle, school and city officials recently made the shift. Beginning with the 2016-2017 school year, the district moved the official start times for middle and high schools nearly an hour later, from 7:50 a.m. to 8:45 a.m. This was no easy feat; it meant rescheduling extracurricular activities and bus routes. But the bottom line goal was met: Teenagers used the extra time to sleep in. Researchers at the University of Washington studied the high school students both before and after the start-time change. Their findings appear in a study published Wednesday in the journal Science Advances. They found students got 34 minutes more sleep on average with the later school start time. This boosted their total nightly sleep from 6 hours and 50 minutes to 7 hours and 24 minutes. "This study shows a significant improvement in the sleep duration of students, all by delaying school start times so they're more in line with the natural wake-up times of adolescents," says senior author Horacio de la Iglesia, a University of Washington researcher and professor of biology. The study also found an improvement in grades and a reduction in tardiness and absences.

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: 26660 - Posted: 10.01.2019

By Tina Hesman Saey Mice (and maybe people) may metabolize food according to daily, circadian rhythms set by gut bacteria. Microbes in the small intestine of mice rhythmically dictate when fat is taken up by cells that line the organ, researchers report. The study, described in the Sept. 27 Science, details how gut microbes influence a host’s metabolism. If the findings carry over to people, the research may give clues to why jet lag and night-shift work, which can throw off circadian rhythms, often lead to obesity, diabetes and other health problems. Researchers knew that human cells have molecular clocks that time 24-hour circadian cycles of metabolism (SN: 11/8/18), and that gut microbes in the colon follow their hosts’ biological beat (SN: 10/16/14). But the new study finds that, at least in the small intestine, microbes can set rhythms for host cells to follow. That work was done in mice, but the process may work similarly in people. The new research “is helping us appreciate just how intertwined are the metabolisms of the microbiota and their mammalian hosts,” says microbiologist and immunologist Andrew Gewirtz of Georgia State University in Atlanta who was not involved in the work. “It’s a very intimate interaction, regulating things as basic as circadian rhythms, which was quite a surprise.” © Society for Science & the Public 2000–2019.

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: 26651 - Posted: 09.27.2019

By Jane E. Brody Early to bed, early to rise — a fine plan for a dairy farmer who has to get up long before dawn to milk the cows. But if you’re someone who works all day with stocks and clients and may want to enjoy an evening out now and then, it would be better not to be getting up at 2 a.m. and have to struggle to stay awake through dinner or a show. Such is the challenge faced by a friend who has what sleep specialists call an advanced sleep phase. Her biological sleep-wake cycle, or circadian rhythm, is out of sync with the demands of the modern world. My friend, who asked to remain anonymous, has always been an early riser, even as a teenager. Getting up at 5 was an advantage in high school — she never had to worry about being late. But as she aged, her nights kept getting shorter. Now at age 63 she’s ready to go to sleep before 9 p.m., but that rarely fits with the demands of her life. No matter how delayed her bedtime, she gets up by 4 in the morning — and sometimes as early as 1:30 — and can’t get back to sleep. She said that given her stimulating job as an investment products specialist, she’s not sleepy during the day, nor does she nap. Still, she’s concerned about her short nights, partly because she’s read that insufficient sleep — especially not enough REM sleep, when dreams occur — has been linked to a possible increased risk of Alzheimer’s disease. She knows that late dinners, especially with wine, contribute to her sleep problem. But it’s also likely that her lifelong dairy-farmer sleep pattern is programmed by her genes, not the result of unavoidable disruptions or unwise living habits. And, it seems, her early-to-sleep, early-to-wake rhythm may not be as extremely rare as has long been believed. In a new study in the journal Sleep by researchers in San Francisco, Salt Lake City and Madison, Wis., of more than 2,400 patients who visited a sleep clinic for complaints like sleep apnea or insomnia, a small number of them were found to have a previously unrecognized familial form of advanced sleep phase, a kind of permanent jet lag that the study showed often runs in families. © 2019 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: 26488 - Posted: 08.12.2019

By Diana Kwon Your brain is a bit like a concert hall. To drive our cognitive processes, several groups of neurons need to become active—and, like the various sections of an orchestra, work in harmony to produce the symphony of computations that allow us to perceive and interact with our surroundings. As with an orchestra, the brain likely requires a conductor to keep all its active parts in sync. There are neuroscientists who think that gamma rhythms, fast brain waves that fluctuate at a frequency of approximately 40 cycles per second, play this role. By ticking at regular intervals, these oscillations are thought to act like a clock that coordinates information transfer from one group of neurons to another. There is ample evidence suggesting that gamma waves are important for the brain's computations: decades of studies in humans and other animals have found these patterns in many parts of brain and have associated them with a range of cognitive processes, such as attention and the mental scratchpad of working memory. Some studies have even linked disturbances in these oscillations to various neurological diseases, including schizophrenia and Alzheimer's. But a consensus does not exist. Some neuroscientists think that these gamma waves may not do much at all. Rather than a relevant physiological signal, one camp believes that these rhythms are simply “an exhaust fume of computation,” says Chris Moore, a neuroscientist at the Carney Institute for Brain Science at Brown University. In the same way your car releases emissions each time you drive it—the gamma signal could be perfectly correlated with brain activity, but not provide any meaningful contribution to the actual function of the car, he explains. © 2019 Scientific American

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: 26429 - Posted: 07.19.2019

Erin Wayman Crowds of people gather to watch an evening spectacle on beaches in Southern California: Twice a month, typically from March through August, the sand becomes carpeted with hundreds or thousands of California grunion. Writhing, flopping, silvery sardine look-alikes lunge as far onto shore as possible. As the female fish dig their tails into the sand and release eggs, males wrap around females and release sperm to fertilize those eggs. About 10 days later, the eggs hatch and the little grunion get washed out to sea. This mating ritual is set to the tides, with hatching timed to the arrival of the peak high tide every two weeks. But the ultimate force choreographing this dance is the moon. Many people know that the moon’s gravitational tug on the Earth drives the tides, and with them, the life cycles of coastal creatures. Yet the moon also influences life with its light. This story is part of a special report celebrating humans’ enduring fascination with the moon and exploring the many ways it affects life on Earth. More articles will be published in the coming weeks. See all the articles, plus our 1969 coverage of Apollo 11, here. For people living in cities ablaze with artificial lights, it can be hard to imagine how dramatically moonlight can change the nocturnal landscape. Out in the wild, far from any artificial light, the difference between a full moon and a new moon (when the moon appears invisible to us) can be the difference between being able to walk outside without a flashlight and not being able to see the hand in front of your face. |© Society for Science & the Public 2000 - 2019.

Related chapters from BN8e: Chapter 14: Biological Rhythms, Sleep, and Dreaming
Related chapters from MM:Chapter 10: Biological Rhythms and Sleep
Link ID: 26398 - Posted: 07.08.2019

Bryan Clark Last spring, a study set the internet ablaze with sensational headlines promising an early death for those with nontraditional sleep schedules. It wasn’t the conclusion of the study, or its researchers. But in the bombastic world of science reporting, it didn’t really matter. Originally published in the journal Chronobiology International, the study looked at the chronotypes — a means of classifying one’s predisposition for sleeping at certain hours — of more than 430,000 people over a six-and-a-half-year period. Scouring data from the National Health Service in England and the NHS Central Register in Scotland, researchers sought to find out what, if any, negative health impacts awaited those with a night-owl schedule. After sorting nearly half a million people into four groups — definite larks (larks are early birds, those most likely to rise with the sun), definite owls (those more likely to retire to bed with the sun than to wake with it), moderate larks and moderate owls — researchers reported some troubling findings. More than 10,000 participants died during the study period. Of those deaths, the bulk seemed to be the result of natural causes. The study didn’t necessarily seek to link death with sleep deprivation, but rather to “comorbidity” — the occurrence in one person of two or more conditions, such as psychological or neurological disorders, diabetes and the like. With each incremental shift toward a night-owl schedule, comorbidities became more common, increasing the risk of an early death. But while saying that night owls are going to die early makes for an eye-catching headline, the real story isn’t quite that simple. The story behind the study It’s evident that owls’ nontraditional schedules put them at risk of significant health problems. Nearly every study on this chronotype has returned troubling findings. © 2019 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: 26267 - Posted: 05.24.2019

By Christopher Ingraham Sleep scientist Matthew Walker has observed that “human beings are the only species that deliberately deprive themselves of sleep for no apparent gain.” We stay up late to watch our favorite TV shows. We wake up early to get to work or school on time. And twice a year we change our clocks, to the bewilderment of our circadian rhythms. We also set up conflicts between our natural and social clocks in other, less obvious ways, a fact underscored in research published this month in the Journal of Health Economics. It turns out, the study found, that living on the wrong side of a time zone’s boundary can have negative consequences on a person’s health and wallet. The culprit? More natural light in the evening hours. To understand the study, co-authored by Osea Giuntella of the University of Pittsburgh and Fabrizio Mazzonna of the Universita della Svizzera Italiana, it is important to understand how time zones affect local sunset times. Traveling east to west, sunrise and sunset times get later, as the map above shows. Panama City, Fla., for instance, is located on the far eastern end of the Central time zone, while Pecos, Tex., sits on the far western side. This week, the sun set in Panama City about 7:12 p.m. Central time. In Pecos, it set more than an hour later, at 8:25 p.m. Sunset is a powerful biological trigger: The fading of natural light causes the body to release melatonin, a hormone that induces drowsiness. As a result, people on the eastern side of a time zone, where the sun sets earlier, tend to go to bed earlier than those on the western side. The data below, derived from about 1 million users of the now-defunct sleep tracker Jawbone, illustrates this point, showing how bedtimes shift from east to west, with a sharp reset happening once you cross into a new time zone. © 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: 26161 - Posted: 04.22.2019

By Steph Yin For animals that hibernate, making it to spring is no small feat. Torpor — the state of reduced bodily activity that occurs during hibernation — is not restful. By the time they emerge, hibernating animals are often sleep-deprived: Most expend huge bursts of energy to arouse themselves occasionally in the winter so their body temperatures don’t dip too low. This back-and-forth is exhausting, and hibernators do it with little to no food and water. By winter’s end, some have shed more than half their body weight. But just because it’s spring doesn’t mean it’s time to celebrate. Spring means getting ready for the full speed of summer — and after spending a season in slow motion, that requires some ramping up. Here’s a look at what different animals have on the agenda after coming out of winter’s slumber. Black bears emerge from their dens in April, but stay lethargic for weeks. During this so-called walking hibernation, they sleep plenty and don’t roam very far. Though they have lost up to one-third of their body weight over winter, they don’t have a huge appetite right away — their metabolism is not yet back to normal. They snack mostly on pussy willows and bunches of snow fleas. In January or February, some females give birth, typically to two or three cubs. New mothers continue to hibernate, but they go in and out of torpor, staying alert enough to respond to their cubs’ cries. When they emerge from their dens, mama bears find trees with rough bark that her cubs can easily climb for safety. © 2019 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: 26112 - Posted: 04.04.2019

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