Chapter 14. Biological Rhythms, Sleep, and Dreaming

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


Links 1 - 20 of 1171

By Agata Blaszczak-Boxe When it comes to lab animal welfare, rats and mice aren’t the only creatures of concern. In 2013, the European Union mandated that cephalopods—a group that includes octopuses and squid—be treated humanely when used for scientific research. In response, researchers have figured out how to anesthetize octopuses so the animals do not feel pain while being transported and handled during scientific experiments, for instance those examining their behavior, physiology, and neurobiology, as well as their use in aquaculture. In a study published online this month in the Journal of Aquatic Animal Health, researchers report immersing 10 specimens of the common octopus (Octopus vulgaris) in seawater with isoflurane, an anesthetic used in humans. They gradually increased the concentration of the substance from 0.5% to 2%. The investigators found that the animals lost the ability to respond to touch and their color paled, which means that their normal motor coordination of color regulation by the brain was lost, concluding that the animals were indeed anesthetized. The octopuses then recovered from the anesthesia within 40 to 60 minutes of being immersed in fresh seawater without the anesthetic, as they were able to respond to touch again and their color was back to normal. The researchers captured the anesthetization process on video, shown above. © 2014 American Association for the Advancement of Science.

Keyword: Animal Rights
Link ID: 20311 - Posted: 11.15.2014

By Dr. Catherine A. Madison “Now why did I walk into this room? Oh, yes, looking for my …” This scenario, familiar to many, is most often a sign of normal aging — or of having too much on our minds. But when these events seem to be happening frequently, is it a more serious problem, such as Alzheimer’s disease or another dementia? Even more importantly, are there good health habits that can help lower the risk of these neurodegenerative conditions? Research continues to demonstrate that healthy lifestyles lower one’s risk of developing cognitive decline later in life. Wise food choices and lots of exercise are a good base, along with learning new material and keeping socially connected. But another key element to brain health is good sleep. We may take sleep for granted, but research suggests this is not a passive process. There is a growing consensus that sleep is linked to learning, memory, nerve cell remodeling and repair. Evidence also suggests lack of sleep can contribute to mood and immune disorders, as well as to a decline in overall health. Most of us have read the dos and don’ts of good sleep hygiene: avoid napping, don’t drink alcohol or caffeine close to bedtime, avoid late-evening exercise and sleep in a room that is quiet, dark and cool. We’ve also been told about sleep cycles, in which we typically progress from light sleep early in the night to slow wave sleep with rapid eye movement, or REM, later on. We need a balance of sleep cycles for optimal health.

Keyword: Sleep; Aggression
Link ID: 20293 - Posted: 11.10.2014

By James Gallagher Health editor, BBC News website Working antisocial hours can prematurely age the brain and dull intellectual ability, scientists warn. Their study, in the journal Occupational and Environmental Medicine, suggested a decade of shifts aged the brain by more than six years. There was some recovery after people stopped working antisocial shifts, but it took five years to return to normal. Experts say the findings could be important in dementia, as many patients have disrupted sleep. The body's internal clock is designed for us to be active in the day and asleep at night. The damaging effects on the body of working against the body clock, from breast cancer to obesity, are well known. Now a team at the University of Swansea and the University of Toulouse has shown an impact on the mind as well. Three thousand people in France performed tests of memory, speed of thought and wider cognitive ability. The brain naturally declines as we age, but the researchers said working antisocial shifts accelerated the process. Those with more than 10 years of shift work under their belts had the same results as someone six and a half years older. The good news is that when people in the study quit shift work, their brains did recover. Even if it took five years. Dr Philip Tucker, part of the research team in Swansea, told the BBC: "It was quite a substantial decline in brain function, it is likely that when people trying to undertake complex cognitive tasks then they might make more mistakes and slip-ups, maybe one in 100 makes a mistake with a very large consequence, but it's hard to say how big a difference it would make in day-to-day life." BBC © 2014

Keyword: Biological Rhythms; Aggression
Link ID: 20281 - Posted: 11.05.2014

By Paula Span First, an acknowledgment: Insomnia bites. S. Bliss, a reader from Albuquerque, comments that even taking Ativan, he or she awakens at 4:30 a.m., can’t get back to sleep and suffers “a state of sleep deprivation and eventually a kind of walking exhaustion.” Molly from San Diego bemoans “confusion, anxiety, exhaustion, depression, loss of appetite, frankly a loss of will to go on,” all consequences of her sleeplessness. She memorably adds, “Give me Ambien or give me death.” Marciacornute reports that she’s turned to vodka (prompting another reader to wonder if Medicare will cover booze). After several rounds of similar laments here (and not only here; insomnia is prevalent among older adults), I found the results of a study by University of Chicago researchers particularly striking. What if people who report sleep problems are actually getting enough hours of sleep, overall? What if they’re not getting significantly less sleep than people who don’t complain of insomnia? Maybe there’s something else going on. It has always been difficult to ascertain how much people sleep; survey questions are unreliable (how can you tell when you’ve dozed off?), and wiring people with electrodes creates such an abnormal situation that the results may bear little resemblance to ordinary nightlife. Enter the actigraph, a wrist-motion monitor. “The machines have gotten better, smaller, less clunky and more reliable,” said Linda Waite, a sociologist and a co-author of the study. By having 727 older adults across the United States (average age: almost 72) wear actigraphs for three full days, Dr. Waite and her colleagues could tell when subjects were asleep and when they weren’t. Then they could compare their reported insomnia to their actual sleep patterns. Overall, in this random sample, taken from an ongoing national study of older adults, people didn’t appear sleep-deprived. They fell asleep at 10:27 p.m. on average, and awakened at 6:22 a.m. After subtracting wakeful periods during the night, they slept an average seven and a quarter hours. But averages don’t tell us much, so let’s look more closely at their reported insomnia. “What was surprising to us is that there’s very little association between people’s specific sleep problems and what the actigraph shows,” Dr. Waite said. © 2014 The New York Times Company

Keyword: Sleep; Aggression
Link ID: 20250 - Posted: 10.28.2014

Scientists say they have identified the underlying reason why some people are prone to the winter blues, or seasonal affective disorder (SAD). People with Sad have an unhelpful way of controlling the "happy" brain signalling compound serotonin during winter months, brain scans reveal. As the nights draw in, production of a transporter protein ramps up in Sad, lowering available serotonin. The work will be presented this week at a neuropsychopharmacology conference. The University of Copenhagen researchers who carried out the trial say their findings confirm what others have suspected - although they only studied 11 people with Sad and 23 healthy volunteers for comparison. Using positron emission tomography (PET) brain scans, they were able to show significant summer-to-winter differences in the levels of the serotonin transporter (SERT) protein in Sad patients. The Sad volunteers had higher levels of SERT in the winter months, corresponding to a greater removal of serotonin in winter, while the healthy volunteers did not. Winter depression Lead researcher, Dr Brenda Mc Mahon, said: "We believe that we have found the dial the brain turns when it has to adjust serotonin to the changing seasons. BBC © 2014

Keyword: Depression; Aggression
Link ID: 20225 - Posted: 10.21.2014

By Jane E. Brody Within a week of my grandsons’ first year in high school, getting enough sleep had already become an issue. Their concerned mother questioned whether lights out at midnight or 1 a.m. and awakening at 7 or 7:30 a.m. to get to school on time provided enough sleep for 14-year-olds to navigate a demanding school day. The boys, of course, said “yes,” especially since they could “catch up” by sleeping late on weekends. But the professional literature on the sleep needs of adolescents says otherwise. Few Americans these days get the hours of sleep optimal for their age, but experts agree that teenagers are more likely to fall short than anyone else. Researchers report that the average adolescent needs eight and a half to nine and a half hours of sleep each night. But in a poll taken in 2006 by the National Sleep Foundation, less than 20 percent reported getting that much rest on school nights. With the profusion of personal electronics, the current percentage is believed to be even worse. A study in Fairfax, Va., found that only 6 percent of children in the 10th grade and only 3 percent in the 12th grade get the recommended amount of sleep. Two in three teens were found to be severely sleep-deprived, losing two or more hours of sleep every night. The causes can be biological, behavioral or environmental. And the effect on the well-being of adolescents — on their health and academic potential — can be profound, according to a policy statement issued in August by the American Academy of Pediatrics. “Sleep is not optional. It’s a health imperative, like eating, breathing and physical activity,” Dr. Judith A. Owens, the statement’s lead author, said in an interview. “This is a huge issue for adolescents.” © 2014 The New York Times Company

Keyword: Sleep; Aggression
Link ID: 20224 - Posted: 10.21.2014

By Benedict Carey Sleep. Parents crave it, but children and especially teenagers, need it. When educators and policymakers debate the relationship between sleep schedules and school performance and — given the constraints of buses, sports and everything else that seem so much more important — what they should do about it, they miss an intimate biological fact: Sleep is learning, of a very specific kind. Scientists now argue that a primary purpose of sleep is learning consolidation, separating the signal from the noise and flagging what is most valuable. School schedules change slowly, if at all, and the burden of helping teenagers get the sleep they need is squarely on parents. Can we help our children learn to exploit sleep as a learning tool (while getting enough of it)? Absolutely. There is research suggesting that different kinds of sleep can aid different kinds of learning, and by teaching “sleep study skills,” we can let our teenagers enjoy the sense that they’re gaming the system. Start with the basics. Sleep isn’t merely rest or downtime; the brain comes out to play when head meets pillow. A full night’s sleep includes a large dose of several distinct brain states, including REM sleep – when the brain flares with activity and dreams – and the netherworld of deep sleep, when it whispers to itself in a language that is barely audible. Each of these states developed to handle one kind of job, so getting sleep isn’t just something you “should do” or need. It’s far more: It’s your best friend when you want to get really good at something you’ve been working on. So you want to remember your Spanish vocabulary (or “How I Met Your Mother” trivia or Red Sox batting averages)? © 2014 The New York Times Company

Keyword: Sleep; Aggression
Link ID: 20216 - Posted: 10.18.2014

By CATHERINE SAINT LOUIS Many cases of so-called crib death, about one in eight, occur among infants who have been placed on sofas, researchers reported on Monday. Dr. Jeffrey Colvin, a pediatrician at Children’s Mercy Hospital in Kansas City, Mo., and his colleagues analyzed data on 7,934 sudden infant deaths in 24 states, comparing those that occurred on sofas with those in cribs, bassinets or beds. Previous research had shown that couches were particularly hazardous for infants. The new analysis, published in the journal Pediatrics, tried to identify factors significant in these deaths. “It’s not only one risk that’s higher relative to other sleep environments,” said Barbara Ostfeld, a professor of pediatrics at Rutgers Robert Wood Johnson Medical School who was not involved in the new study. “It’s multiple risks.” Nearly three-quarters of the deaths occurred among infants age 3 months or younger, the researchers found. Pediatricians have long advised putting infants to sleep only on their backs, alone and on a firm, flat surface without a pillow. The new study found parents were more likely to lay their infants face down on a sofa than, for instance, face down in a crib. There’s a “fallacy that if I’m awake or watching, SIDS won’t happen,” Dr. Colvin said, referring to sudden infant death syndrome. © 2014 The New York Times Company

Keyword: Sleep; Aggression
Link ID: 20197 - Posted: 10.13.2014

BY Bethany Brookshire We all need sleep, but attaining it can be delicate. Insomniacs can’t fall or stay asleep. Travelers suffer from jetlag. Anxiety keeps people up at night. Or maybe it’s just that jackhammer running across the street keeping your eyes open. Some people turn to earplugs, dark curtains or alcohol to soothe them to sleep. But others go to the supplement aisle and pick up melatonin. The hormone melatonin is secreted from our brains at night and helps regulate sleep. But this chemical is not restricted to humans, or even to mammals. The roots of melatonin’s role in our nightly slumbers go back much further in evolutionary history. A new paper focuses in on the role of melatonin in tiny marine creatures called zooplankton. It turns out that these animals use melatonin just as much as we do, suggesting that the origins of sleeplike behavior may lie under the sea. “For every system and feature that makes a human or other animal today, you can ask the question: Where did it start? How did it begin? What was its first role and function, and how did it become more complex?” says study coauthor Detlev Arendt, a zoologist at the University of Heidelberg in Germany. Arendt’s laboratory has been studying the answers to these questions in the marine ragworm Platynereis dumerilii. This unassuming, centipede-like, ocean-dwelling worm produces larvae that float through the open water as zooplankton. These small larvae propel themselves up and down in the water column with movements of their cilia, slender, hair-like appendages that protrude out from the organisms. © Society for Science & the Public 2000 - 2014.

Keyword: Biological Rhythms; Aggression
Link ID: 20180 - Posted: 10.08.2014

By CLAIRE MALDARELLI Whether it’s lying wide awake in the middle of the night or falling asleep at an international business meeting, many of us have experienced the funk of jet lag. New research has uncovered some of the mysteries behind how our cells work together to maintain one constant daily rhythm, offering the promise of defense against this disorienting travel companion. Many organisms, including humans and fruit flies, have pacemaker neurons — specialized cells in the brain that have their own molecular clocks and oscillate in 24-hour cycles. But in order for an organism to regulate itself, all of these internal clocks must tick together to create one master clock. While scientists understood how individual neurons set their own clock, they didn’t know how that master clock was set. Working with young fruit flies, whose neuronal system is simpler than adults with fewer cells and easier to study, the researchers found that two types of neurons, which they called dawn cells and dusk cells, maintain a continuous cycle. As the sun rises, special “timeless” proteins, as they’re called, help the dawn cells to first signal to each other and then signal to the dusk cells. Then as the sun sets, proteins help the dusk cells signal to each other and then signal back to the dawn cells. Each signal tells the cells to synchronize with each other. Together, these two distinct signals drive the daily sleep and wake cycle. “This really shifts our view of these cells as super strong, independent oscillators to much more of a collective group working together to keep time,” said Justin Blau, a neurobiologist at New York University and co-author of the study. © 2014 The New York Times Company

Keyword: Sleep; Aggression
Link ID: 20172 - Posted: 10.07.2014

Carl Zimmer As much as we may try to deny it, Earth’s cycle of day and night rules our lives. When the sun sets, the encroaching darkness sets off a chain of molecular events spreading from our eyes to our pineal gland, which oozes a hormone called melatonin into the brain. When the melatonin latches onto neurons, it alters their electrical rhythm, nudging the brain into the realm of sleep. At dawn, sunlight snuffs out the melatonin, forcing the brain back to its wakeful pattern again. We fight these cycles each time we stay up late reading our smartphones, suppressing our nightly dose of melatonin and waking up grumpy the next day. We fly across continents as if we could instantly reset our inner clocks. But our melatonin-driven sleep cycle lags behind, leaving us drowsy in the middle of the day. Scientists have long wondered how this powerful cycle got its start. A new study on melatonin hints that it evolved some 700 million years ago. The authors of the study propose that our nightly slumbers evolved from the rise and fall of our tiny oceangoing ancestors, as they swam up to the surface of the sea at twilight and then sank in a sleepy fall through the night. To explore the evolution of sleep, scientists at the European Molecular Biology Laboratory in Germany study the activity of genes involved in making melatonin and other sleep-related molecules. Over the past few years, they’ve compared the activity of these genes in vertebrates like us with their activity in a distantly related invertebrate — a marine worm called Platynereis dumerilii. The scientists studied the worms at an early stage, when they were ball-shaped 2-day-old larvae. The ocean swarms with juvenile animals like these. Many of them spend their nights near the ocean surface, feeding on algae and other bits of food. Then they spend the day at lower depths, where they can hide from predators and the sun’s ultraviolet rays. © 2014 The New York Times Company

Keyword: Sleep; Aggression
Link ID: 20154 - Posted: 10.02.2014

by Sarah Zielinski Small, silver fish called Mexican tetra (Astyanax mexicanus) live in some Texas and Mexican rivers. Some members of the species — eyeless and blind — can be found in nearby freshwater caves. Sometimes the sighted fish wash into a cave, but they don’t do nearly as well as their blind brethren. Any surface dweller unlucky enough to end up in the dark would have some disadvantages: It would have to adapt to the loss of light and forage for unfamiliar foods, which may be not as abundant as those found in their home waters. But the fish’s biggest disadvantage may be its metabolism. Blind cavefish have lost their circadian rhythms and have developed more efficient metabolisms than the fish that live in the light, researchers report September 24 in PLOS ONE. To measure tetras’ metabolism, Damian Moran and colleagues at Lund University in Sweden placed fish in a contraption that let the fish swim in place while the researchers tracked their oxygen consumption, a measure of their metabolism. Surface and cave fish were placed in the tank under constant darkness or 12-hour light-and-dark cycles for 7 or 8 days. Then the researchers compared how the fish did under the different light regimes. All the fish took a few days to acclimate to the laboratory conditions. In the light-and-dark conditions, surface fish showed a clear circadian pattern to their oxygen consumption. These fish ramped up their metabolism by about 20 percent during the day. That increase in metabolism would let them have more energy for their hunts and feeding, which take place in the light. © Society for Science & the Public 2000 - 2014

Keyword: Biological Rhythms
Link ID: 20134 - Posted: 09.30.2014

Christie Nicholson reports. Shakespeare called sleep the chief nourisher in life’s feast. But today we know it’s so much more. Insufficient sleep contributes to the risk of cardiovascular disease, diabetes and obesity. And now a study finds that too little or too much sleep are both associated with a significant increase in sick days away from work. Almost 4,000 men and women between 30 and 64 years old (in Finland) participated in the study, which followed them for seven years. The research revealed that the absence from work due to illness increased dramatically for those who said they slept less than 6 hours or more than 9 hours per night. The sleep time that was associated with the lowest number of sick days was 7 hours 38 minutes for women and 7 hours 46 minutes for men. The study is in the journal Sleep. [Tea Lallukka, Sleep and Sickness Absence: A Nationally Representative Register-Based Follow-Up Study] Of course these findings are associative and not necessarily causal. Other factors may be responsible for the under- or oversleeping to begin with. But sleep patterns are still a warning sign for increased illness and health complications. Shakespeare put it best: Sleep…that knits up the ravell’d sleave of care. © 2014 Scientific American

Keyword: Sleep
Link ID: 20133 - Posted: 09.30.2014

By Tara Parker-Pope The most reliable workers are those who get seven to eight hours of sleep each night, a new study shows. Researchers from Finland analyzed the sleep habits and missed work days among 3,760 men and women over about seven years. The workers ranged in age from 30 to 64 at the start of the study. The researchers found that the use of sick days was associated with the worker’s sleep habits. Not surprisingly, they found that people who did not get enough sleep because of insomnia or other sleep problems were more likely to miss work. But notably, getting a lot of extra sleep was also associated with missed work. The workers who were most likely to take extra sick days were those who slept five hours or less or 10 hours or more. Short sleepers and long sleepers missed about five to nine more days of work than so-called optimal sleepers, workers who managed seven to eight hours of sleep each night. The workers who used the fewest number of sick days were women who slept an average of 7 hours 38 minutes a night and men who slept an average of 7:46. The study results were published in the September issue of the medical journal Sleep. © 2014 The New York Times Company

Keyword: Sleep
Link ID: 20074 - Posted: 09.15.2014

By Jennifer Balmer Each summer, leatherback sea turtles (Dermochelys coriacea) migrate thousands of kilometers from their tropical breeding grounds to feed in cooler waters. Yet how the animals know when to begin their long journey back south at the end of the season has mostly remained a mystery. New findings, to be published in an upcoming issue of the Journal of Experimental Marine Biology and Ecology, suggest that leatherback sea turtles may be able to sense seasonal changes in sunlight by means of an unpigmented spot on the crown of their head—known as the pink spot (pictured). Researchers conducted an examination of the anatomical structures beneath the pink spot and found that the layers of bone and cartilage were remarkably thinner than in other areas of the skull. This thin region of the skull allows the passage of light through to an area of the brain, called the pineal gland, that acts as biological clock, regulating night-day cycles and seasonal patterns of behavior. The authors suggest that the lack of pigment in the crowning pink spot and thin skull region underlying it act as a “skylight,” allowing the turtles to sense the subtle changes in sunlight that accompany changing seasons, signaling them to return south when autumn approaches. © 2014 American Association for the Advancement of Science

Keyword: Animal Migration; Aggression
Link ID: 20069 - Posted: 09.13.2014

by Simon Makin Talking in your sleep might be annoying, but listening may yet prove useful. Researchers have shown that sleeping brains not only recognise words, but can also categorise them and respond in a previously defined way. This could one day help us learn more efficiently. Sleep appears to render most of us dead to the world, our senses temporarily suspended, but sleep researchers know this is a misleading impression. For instance, a study published in 2012 showed that sleeping people can learn to associate specific sounds and smells. Other work has demonstrated that presenting sounds or smells during sleep boosts performance on memory tasks – providing the sensory cues were also present during the initial learning. Now it seems the capabilities of sleeping brains stretch even further. A team led by Sid Kouider from the Ecole Normale Supérieur in Paris trained 18 volunteers to classify spoken words as either animal or object by pressing buttons with their right or left hand. Brain activity was recorded using EEG, allowing the researchers to measure the telltale spikes in activity that indicate the volunteers were preparing to move one of their hands. Since each hand is controlled by the motor cortex on the opposite side of the brain, these brainwaves can be matched to the intended hand just by looking at which side of the motor cortex is active. © Copyright Reed Business Information Ltd.

Keyword: Sleep; Aggression
Link ID: 20066 - Posted: 09.12.2014

By Helen Briggs Health editor, BBC News website Long-term use of pills for anxiety and sleep problems may be linked to Alzheimer's, research suggests. A study of older Canadian adults found that past benzodiazepine use for three months or more was linked to an increased risk (up to 51%) of dementia. NHS guidelines say the drugs should be used for eight to 12 weeks at most. The French-Canadian team says while the link is not definitive, it is another warning that treatments should not exceed three months. "Benzodiazepine use is associated with an increased risk of Alzheimer's disease," lead researcher, Sophie Billioti de Gage of the University of Bordeaux, France, and colleagues wrote in the BMJ. "Unwarranted long-term use of these drugs should be considered as a public health concern." The study involved about 2,000 cases of Alzheimer's disease in adults aged over 66 living in Quebec. All had been prescribed benzodiazepines. They were compared with about 7,000 healthy people of the same age living in the same community. While an increased risk was found in those on benzodiazepines, the nature of the link was unclear. Dr Eric Karran, director of research at Alzheimer's Research UK, said: "This study shows an apparent link between the use of benzodiazepines and Alzheimer's disease although it's hard to know the underlying reason behind the link. BBC © 2014

Keyword: Alzheimers; Aggression
Link ID: 20057 - Posted: 09.10.2014

By Smitha Mundasad Health reporter, BBC News More than 300 people a year in the UK and Ireland report they have been conscious during surgery - despite being given general anaesthesia. In the largest study of its kind, scientists suggests this happens in one in every 19,000 operations. They found episodes were more likely when women were given general anaesthesia for Caesarean sections or patients were given certain drugs. Experts say though rare, much more needs to be done to prevent such cases. Led by the Royal College of Anaesthetists and Association of Anaesthetists of Great Britain and Ireland, researchers studied three million operations over a period of one year. More than 300 people reported they had experienced some level of awareness during surgery. Most episodes were short-lived and occurred before surgery started or after operations were completed. But some 41% of cases resulted in long-term psychological harm. Patients described a variety of experiences - from panic and pain to choking - though not all episodes caused concern. The most alarming were feelings of paralysis and being unable to communicate, the researchers say. One patient, who wishes to remain anonymous, described her experiences of routine orthodontic surgery at the age of 12. She said: "I could hear voices around me and I realised with horror that I had woken up in the middle of the operation but couldn't move a muscle. BBC © 2014

Keyword: Consciousness; Aggression
Link ID: 20055 - Posted: 09.10.2014

Greta Kaul, Stanford researchers say poor sleep may be an independent risk factor for suicide in adults over 65. Researchers used data from a previous epidemiological study to compare the sleep quality of 20 older adults who committed suicide and 400 who didn't, over 10 years. Researchers found that those who didn't sleep well were 1.4 times more likely to commit suicide within a decade. Older adults have disproportionately high suicide rates in the first place, especially older men. The Stanford researchers believe that on its own, sleeping poorly could be a risk factor for suicide later in life. It may even be a more powerful predictor of suicide risk than symptoms of depression. They found that the strongest predictor of suicide was the combination of bad sleep and depression. Unlike many biological, psychological and social risk factors for suicide, sleep disorders tend to be treatable, said Rebecca Bernert, the lead author of the study. Sleep disorders are also less stigmatized than other suicide risk factors. Bernert is now studying whether treating insomnia is effective in preventing depression and suicide. The study was published in JAMA Psychiatry in August. © 2014 Hearst Communications, Inc.

Keyword: Depression; Aggression
Link ID: 20024 - Posted: 09.03.2014

By Meeri Kim The pervasive glow of electronic devices may be an impediment to a good night’s sleep. That’s particularly noticeable now, when families are adjusting to early wake-up times for school. Teenagers can find it especially hard to get started in the morning. For nocturnal animals, it spurs activity. For daytime species such as humans, melatonin signals that it’s time to sleep. As lamps switch off in teens’ bedrooms across America, the lights from their computer screens, smartphones and tablets often stay on throughout the night. These devices emit light of all colors, but it’s the blues in particular that pose a danger to sleep. Blue light is especially good at preventing the release of melatonin, a hormone associated with nighttime. Ordinarily, the pineal gland, a pea-size organ in the brain, begins to release melatonin a couple of hours before your regular bedtime. The hormone is no sleeping pill, but it does reduce alertness and make sleep more inviting. However, light — particularly of the blue variety — can keep the pineal gland from releasing melatonin, thus warding off sleepiness. You don’t have to be staring directly at a television or computer screen: If enough blue light hits the eye, the gland can stop releasing melatonin. So easing into bed with a tablet or a laptop makes it harder to take a long snooze, especially for sleep-deprived teenagers who are more vulnerable to the effects of light than adults. During adolescence, the circadian rhythm shifts, and teens feel more awake later at night. Switching on a TV show or video game just before bedtime will push off sleepiness even later even if they have to be up by 6 a.m. to get to school on time.

Keyword: Biological Rhythms; Aggression
Link ID: 20021 - Posted: 09.02.2014