Chapter 10. Biological Rhythms and Sleep

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Mo Costandi We spend approximately one-third of our lives sleeping, but why sleep is important is a big unanswered question, one which science has only begun to answer recently. We now know, for example, that the brain cleans itself while we sleep, and that long-term memories form during the rapid eye movement (REM) stage of sleep. Your brain is highly active during sleep Sleep can be defined as a temporary state of unconsciousness, during which our responses to the outside world are reduced. Yet, we also know that the brain is active during sleep, and there is growing evidence that it remains highly responsive: For instance, your sleeping brain will respond to your name, categorize words and then prepare appropriate actions, and even learn new information. Now, a new study by researchers at UCLA and Tel Aviv University shows that the human brain remains highly responsive to sound during sleep, but it does not receive feedback from higher order areas — sort of like an orchestra with “the conductor missing.” The findings could point to a better understanding of the extent to which the brain processes information in disorders of consciousness such as coma and vegetative states, and to the neural mechanisms of conscious awareness. The missing conductor Hanna Hayat and her colleagues had the rare opportunity to record the activity of cells directly from the brains of 13 patients with drug-resistant epilepsy, who were being evaluated for brain surgery and gave written consent to participate in the study during the evaluation. The researchers implanted depth electrodes in multiple regions of the patients’ brains, primarily to identify the source of their seizures, so that the abnormal tissue could be surgically removed. Over the course of eight overnight sessions and six daytime naps, they played various sounds — including words, sentences and music — to the patients through bedside loudspeakers. They also used standard electroencephalogram (EEG) to monitor the patients’ sleep stages and recorded their sleep behavior with video. © Copyright 2007-2022 & BIG THINK,

Keyword: Sleep
Link ID: 28416 - Posted: 08.03.2022

By Linda Searing Routinely getting a good night’s sleep has been added to the American Heart Association’s list of key components of cardiovascular health, lengthening the list to eight factors the association believes can lead to a longer, higher-quality life without heart disease. Heart disease is the leading cause of death in the United States and has been for the past century, according to the Centers for Disease Control and Prevention. Since 2010, the AHA had focused on seven points: maintaining a healthy weight, not smoking, being physically active, eating a healthy diet, and keeping blood pressure, cholesterol and blood sugar at acceptable levels. Now, however, as indicated in its report published in the journal Circulation, the AHA believes that healthy sleep also should be taken into account. The group’s suggested goal is seven to nine hours of sleep daily for adults, and more for children (eight to 10 hours for 13- to 18-year-olds, nine to 12 hours for 6- to 12-year-olds and 10 to 16 hours for children 5 and younger). Sleep has long been considered vital to good health, both physically and psychologically. Sleep gives the body a needed break to heal and repair itself, setting people up to function normally when they awaken. But a lack of sleep (or poor-quality sleep) puts a person at higher risk for such conditions as diabetes, obesity, high blood pressure and more. © 1996-2022 The Washington Post

Keyword: Sleep
Link ID: 28395 - Posted: 07.14.2022

By Kim Tingley “Time,” when we give it any thought, tends to strike us as extrinsic, a feature of our landscape: We track our passage through it as if traversing an invisible geography, our progress charted by wristwatch, clock, calendar. Humans didn’t invent time, of course, but you might reasonably argue that because we invented the units we use to keep track of it — hours, minutes, seconds — we have every right to tinker with them when we want to. This, at least, was the position the Senate took on March 15, when in a surprise, and surprisingly uncontested, vote it passed the Sunshine Protection Act. The new law would, if the House concurs and the president signs, make daylight saving time permanent, beginning on Nov. 5, 2023. The change has long been a desire of the retail industry because it is convinced that shoppers spend more money when it stays light out later. But lawmakers also seem to have regarded the annual rolling back of the clock as a personal affront: the groggy mornings that result from turning 6 a.m. into 5 a.m., the morale killer for Boston and Billings alike when darkness abruptly descends shortly after 4 in the afternoon. When the yeas prevailed, there was bipartisan applause, as if a particularly hostile foreign adversary had been defeated. What most of those lawmakers very likely didn’t realize was that the enemy was not just outside us — a social agreement about how to label every moment of our existence relative to the sun — it was also inside us, where our internal organs are keeping time, too. In fact, most of our physiological functions are governed by an untold number of carefully synchronized biological clocks that each complete one cycle about every 24 hours. Those cycles are known as circadian rhythms, after the Latin for “about” (circa) and “day” (dies). © 2022 The New York Times Company

Keyword: Biological Rhythms
Link ID: 28394 - Posted: 07.12.2022

Linda Geddes Science correspondent Summer sunshine can leave us feeling hot, sweaty and a bit burnt – but it may also make men hungrier, by triggering the release of an appetite-boosting hormone from fat stores in their skin, data suggests. The study, which was published in the journal Nature Metabolism, adds to growing evidence that the effects of sun exposure may be more complex than first thought. Excessive exposure is well known to increase the risk of skin cancer, but recent studies have suggested moderate exposure may increase life expectancy, on average, by helping to protect against cardiovascular disease and other causes of death. One possibility is that it lowers blood pressure through the release of nitric oxide from the skin, a process that causes blood vessels to relax. Other scientists have attributed the health benefits of sunlight to vitamin D production. Advertisement Wondering whether food consumption could also provide some clues, Carmit Levy, a professor at Tel Aviv University’s department of human molecular genetics and biochemistry, and his colleagues analysed data from 3,000 participants who were enrolled in a national nutrition survey. The researchers found men but not women increased their food intake during the summer months. The effect was not huge – equivalent to eating an extra 300 calories a day – but over time this could be enough to cause weight gain. To investigate further, they exposed male and female volunteers to 25 minutes of midday sunlight on a clear day, and found it triggered an increase in levels of the appetite-boosting hormone ghrelin in the men’s blood but not in women’s. Experiments in mice similarly found that when males were exposed to UVB rays, they ate more, were more motivated to search for food and had increased levels of ghrelin in their blood. No such change was seen in female mice. The trigger for ghrelin release appeared to be DNA damage in skin cells. Oestrogen blocked this effect, which may be why sunlight did not affect females in the same way. © 2022 Guardian News & Media Limited

Keyword: Biological Rhythms; Obesity
Link ID: 28393 - Posted: 07.12.2022

Shogo Sato Anyone who has suffered from jet lag or struggled after turning the clock forward or back an hour for daylight saving time knows all about what researchers call your biological clock, or circadian rhythm – the “master pacemaker” that synchronizes how your body responds to the passing of one day to the next. This “clock” is made up of about 20,000 neurons in the hypothalamus, the area near the center of the brain that coordinates your body’s unconscious functions, like breathing and blood pressure. Humans aren’t the only beings that have an internal clock system: All vertebrates – or mammals, birds, reptiles, amphibians and fish – have biological clocks, as do plants, fungi and bacteria. Biological clocks are why cats are most active at dawn and dusk, and why flowers bloom at certain times of day. Circadian rhythms are also essential to health and well-being. They govern your body’s physical, mental and behavioral changes over each 24-hour cycle in response to environmental cues like light and food. They’re why more heart attacks and strokes occur early in the morning. They’re also why mice that are missing their biological clocks age faster and have shorter lifespans, and people with a mutation in their circadian clock genes have abnormal sleep patterns. Chronic misalignment of your circadian rhythm with external cues, as seen in night-shift workers, can lead to a wide range of physical and mental disorders, including obesity, Type 2 diabetes, cancer and cardiovascular diseases. In short, there is ample evidence that your biological clock is critical to your health. And chronobiologists like me are studying how the day-night cycle affects your body to better understand how you can modify your behaviors to use your internal clock to your advantage. © 2010–2022, The Conversation US, Inc.

Keyword: Biological Rhythms
Link ID: 28386 - Posted: 07.05.2022

By Lisa L. Lewis To any observers, the electrodes were the most visible sign that the Stanford Summer Sleep Camp was a bit out of the ordinary. Joe Oliveira, one of the original campers, recalls that right after check-in, four electrodes were glued to his hair, two taped next to his eyes, and several more by his chin. The electrodes remained in place the whole time. Long cords came out of them that were, “very small, like an iPhone charger,” he told me. During the day, the cords were often tied back and taped together into a compact bundle at the back of his head. The “trodes” (as the campers were called because of their electrode ponytails) attracted their fair share of weird looks on their outings around the university campus. And there was something else peculiar: Like clockwork, every two hours, they all returned to the dorm for “nap tests,” according to Mary Carskadon, who was pursuing her doctorate in neuro- and biobehavioral sciences at Stanford University. In their darkened dorm rooms, all the campers — a mix of kids and teens — would lie quietly for 20 minutes and attempt to fall asleep. Meanwhile, technicians in a nearby control room monitored their brainwaves, eye movements, and chin-muscle activity being transmitted from their electrodes via the cords, which had been plugged into a box near the headboard that had cables linked to a polysomnograph machine in the other room. There, a continuous paper trail issued forth mapping the campers’ data. When the time was up, the campers were roused and unplugged. The counselors recorded their vital signs, then plugged their wires into a second box closer to the dorm room desk and ran the campers through a short series of tests to measure their recall, attention span, and other aspects of alertness and cognitive functioning. Tom Harvey, who worked as a counselor/technician at the camp for several years, recalled a mix of “math tests and memory tests and ‘can you suffer through boredom’ tests.”

Keyword: Sleep; Development of the Brain
Link ID: 28381 - Posted: 06.25.2022

By Oliver Whang The sleep debt collectors are coming. They want you to know that there is no such thing as forgiveness, only a shifting expectation of how and when you’re going to pay them back. You think of them as you lie in bed at night. How much will they ask for? Are you solvent? You fall asleep, then wake up in a cold sweat an hour later. You fall asleep, then wake up, drifting in and out of consciousness until morning. As most every human has discovered, a couple nights of bad sleep is often followed by grogginess, difficulty concentrating, irritability, mood swings and sleepiness. For years, it was thought that these effects, accompanied by cognitive impairments like lousy performances on short-term memory tests, could be primarily attributed to a chemical called adenosine, a neurotransmitter that inhibits electrical impulses in the brain. Spikes of adenosine had been consistently observed in sleep-deprived rats and humans. Adenosine levels can be quickly righted after a few nights of good sleep, however. This gave rise to a scientific consensus that sleep debt could be forgiven with a couple of quality snoozes — as reflected in casual statements like “I’ll catch up on sleep” or “I’ll be more awake tomorrow.” But a review article published recently in the journal Trends in Neurosciences contends that the folk concept of sleep as something that can be saved up and paid off is bunk. The review, which canvassed the last couple of decades of research on long term neural effects of sleep deprivation in both animals and humans, points to mounting evidence that getting too little sleep most likely leads to long-lasting brain damage and increased risk of neurodegenerative disorders like Alzheimer’s disease. © 2022 The New York Times Company

Keyword: Sleep
Link ID: 28380 - Posted: 06.25.2022

Killian Fox Born in Aldershot in 1959, Russell Foster is a professor of circadian neuroscience at Oxford and the director of the Nuffield Laboratory of Ophthalmology. For his discovery of non-rod, non-cone ocular photoreceptors he received numerous awards including the Zoological Society scientific medal. His latest book – the first he has written without a co-author – is Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health. What is circadian neuroscience? It’s the fundamental understanding of how our biology ticks on a 24-hour basis. But also it’s bigger than that – it’s an understanding of how different structures interact within the brain and how different genes and their protein products generate a complex behaviour. And that is then embedded throughout our entire biology. Is it an exciting field? What’s happened over the past 25 years has been a move into understanding how these internal 24-hour oscillations are generated and I think it’s one of the amazing success stories in biomedicine. One of the great aims of neuroscience is identifying different bits of the brain with different functions and here we’ve got one: the suprachiasmatic nucleus (SCN), with 50,000 cells, is the master circadian pacemaker. If you don’t have that, then all of our 24-hour rhythms just disappear. How did you first get interested in circadian research? It was largely through photoreceptors. During my second year as an undergraduate – I did zoology at Bristol – I was reading the extraordinary The Life of Vertebrates by JZ Young and I came across a bit about lampreys. They have a parietal third eye, which mammals don’t have; we only have ocular photoreceptors, whereas fish, reptiles, birds, all have multiple photoreceptors. And I just thought: wow, this is so cool. For my PhD, I was trying to understand how light is detected and measured to regulate the seasonal biology of birds. Then I started to address what seemed a simple question: how are the clocks of mammals regulated? We don’t have weird photoreceptors, we have visual cells that grab light in a fraction of a second and then forget it. So how can that light sensory system also be used to gather light information over long periods of time – dawn-dusk detectors? Way back in the early 1990s, we suggested that there was [an undiscovered photoreceptor] in the eye and there was a huge outcry. © 2022 Guardian News & Media Limited

Keyword: Biological Rhythms; Sleep
Link ID: 28379 - Posted: 06.25.2022

By Anna Gibbs Turns out there is rest for the wicked: Sleepy mosquitoes are more likely to catch up on missed z’s than drink blood, a new study finds. Most people are familiar with the aftermath of a poor night’s sleep. Insects also suffer; for instance, drowsy honeybees struggle to perform their signature waggle dance, and weary fruit flies show signs of memory loss. In the case of sleep-deprived mosquitoes, they give up valuable time for feeding in favor of sleeping overtime, researchers report June 1 in Journal of Experimental Biology. The preference for dozing over dining is surprising given that “we know that mosquitoes love blood a lot,” says Oluwaseun Ajayi, a disease ecologist at the University of Cincinnati. Scientists have long been interested in mosquitoes’ circadian rhythms, the internal clock that determines their sleep and awake times (SN: 10/2/17). Knowing when a mosquito is awake — and biting — is important for understanding and limiting disease transmission. For instance, malaria, often transmitted by nocturnal mosquitoes, is kept under control by slinging netting around beds. But new research suggests that mosquitoes that feed during the day may also spread the disease. It’s challenging to study sleeping bloodsuckers in the lab. That’s partly because awake mosquitoes are aroused by the presence of a meal — the experimenter. And when mosquitoes do fall asleep, they look rather similar to peers that are merely resting to conserve energy. © Society for Science & the Public 2000–2022.

Keyword: Sleep; Evolution
Link ID: 28359 - Posted: 06.09.2022

The Associated Press NEW YORK — Researchers are drawing attention to a rise in poisonings in children involving the sleep aid melatonin — including a big jump during the pandemic. Last year, U.S. poison control centers received more than 52,000 calls about children consuming worrisome amounts of the dietary supplement — a six-fold increase from about a decade earlier. Most such calls are about young children who accidentally got into bottles of melatonin, some of which come in the form of gummies for kids. Parents may think of melatonin as the equivalent of a vitamin and leave it on a nightstand, said Dr. Karima Lelak, an emergency physician at Children's Hospital of Michigan and the lead author of the study published Thursday by the Centers for Disease Control and Prevention. "But really it's a medication that has the potential to cause harm, and should be put way in the medicine cabinet," Lelak said. An increasingly popular over-the-counter sleep aid Melatonin is a hormone that helps control the body's sleep cycle. It has become a popular over-the-counter sleeping aid, with sales increasing 150% between 2016 and 2020, the authors said. In the U.S., melatonin is sold as a supplement, not regulated as a drug. Because melatonin is unregulated, the U.S. Food and Drug Administration doesn't have oversight over the purity of ingredients or the accuracy of dosage claims. Other researchers have found that what's on the label may not match what's actually in the bottle, and some countries have banned the sale of over-the-counter melatonin. © 2022 npr

Keyword: Biological Rhythms; Sleep
Link ID: 28351 - Posted: 06.04.2022

By Peter Kendall As he gets ready for sleep each night, Don Tucker slips on an electrode cap and checks a little computer on his bedside table. Many workers at the private lab, run by the professor emeritus at the University of Oregon, follow the same routine. The experimental device monitors the nightly voyage through sleep. After sensing light sleep for a few minutes, it pulses electric current through the scalp and skull, nudging the brain into that nirvana known as deep sleep. The goal is not just a more restful slumber. Groundbreaking discoveries made in the past decade have revealed that the brain has a power-washing system that switches into high gear during deep sleep, flushing away harmful waste. This nightly cleanup is part of the restorative power of sleep and revives concentration, memory and motor skills. As we age, however, this cleansing system gets sloppier, and it can begin to leave behind some of the metabolic detritus of the day, including the amyloid beta proteins found in the plaque that characterize Alzheimer’s disease and other devastating neurological disorders. The controversial approval of an Alzheimer’s drug reignites the battle over the underlying cause of the disease The stunning revelation in 2012 of this previously unknown brain infrastructure — dubbed the glymphatic system — has ushered in a new age of research and invention not only about sleep but also aging, dementia and brain injury. Nearly 300 research papers were published last year on the glymphatic system. © 1996-2022 The Washington Post

Keyword: Sleep
Link ID: 28346 - Posted: 06.01.2022

If you’ve ever been put under anaesthesia, you might recall the disorienting feeling of blinking your eyes one moment and the next, waking up hours later. Now, findings from a new study illustrate just how profoundly general anaesthesia alters the state of the brain as it induces and maintains unconsciousness. It’s the first paper to track travelling brain waves in subjects all the way through the process of losing to regaining consciousness. An interdisciplinary team has found that the commonly used anaesthetic, propofol, substantially alters how different frequencies of brain waves travel along the cortex – the surface of the brain – and the research has been published in the Journal of Cognitive Neuroscience. Unconsciousness induced by propofol may be in part due to an increase in the strength and direction of slow delta traveling brain waves that disrupt higher-frequency waves associated with cognition. “The rhythms that we associate with higher cognition are drastically altered by propofol,” explains senior author Earl Miller, professor of neuroscience with the Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology (MIT) in the US. “The beta traveling waves seen during wakefulness are pushed aside, redirected by delta traveling waves that have been altered and made more powerful by the anaesthetic,” he says. “The deltas come through like a bull in a china shop.” Conscious brains show a mixture of brain waves of different frequencies, which rotate or travel straight in various directions: you could think of them like the numerous waves on a choppy ocean.

Keyword: Sleep
Link ID: 28314 - Posted: 05.04.2022

By Elizabeth Preston On dry nights, the San hunter-gatherers of Namibia often sleep under the stars. They have no electric lights or new Netflix releases keeping them awake. Yet when they rise in the morning, they haven’t gotten any more hours of sleep than a typical Western city-dweller who stayed up doom-scrolling on their smartphone. Research has shown that people in non-industrial societies — the closest thing to the kind of setting our species evolved in — average less than seven hours a night, says evolutionary anthropologist David Samson at the University of Toronto Mississauga. That’s a surprising number when you consider our closest animal relatives. Humans sleep less than any ape, monkey or lemur that scientists have studied. Chimps sleep around 9.5 hours out of every 24. Cotton-top tamarins sleep around 13. Three-striped night monkeys are technically nocturnal, though really, they’re hardly ever awake — they sleep for 17 hours a day. Samson calls this discrepancy the human sleep paradox. “How is this possible, that we’re sleeping the least out of any primate?” he says. Sleep is known to be important for our memory, immune function and other aspects of health. A predictive model of primate sleep based on factors such as body mass, brain size and diet concluded that humans ought to sleep about 9.5 hours out of every 24, not seven. “Something weird is going on,” Samson says. Research by Samson and others in primates and non-industrial human populations has revealed the various ways that human sleep is unusual. We spend fewer hours asleep than our nearest relatives, and more of our night in the phase of sleep known as rapid eye movement, or REM. The reasons for our strange sleep habits are still up for debate but can likely be found in the story of how we became human. Graph shows average time spent sleep of different primate species. Humans sleep the least at seven hours per night; the three-striped night monkey sleeps the most at nearly 17 hours. © 2022 Annual Reviews

Keyword: Sleep; Evolution
Link ID: 28310 - Posted: 04.30.2022

By Michele Lent Hirsch Sleep problems are a hallmark of modern American life — perhaps never more so than recently. In 2016, the Centers for Disease Control and Prevention found that a third of Americans were getting too little sleep at night. But then came the stressors of the pandemic, job losses, disrupted schedules and closed schools, which kept record numbers of Americans up at night or unable to wake up in the morning. As many as 2 in 3 Americans reported getting either too much or too little sleep, in a survey from the American Psychological Association during the pandemic’s second year. And the insomnia of the past two years may be stubbornly hanging on: Many people continue having more trouble falling asleep or staying asleep or have seen unusual shifts in their sleep schedules. All of this is taking a toll. “These different types of sleep changes seem to be closely related to [problems with] mental health,” says Karianne Dion, a graduate student in clinical psychology at the University of Ottawa. Research she co-wrote, published in the Journal of Sleep Research in 2021, found “worse symptoms of stress, anxiety, and depression” among those who are sleeping less or going to bed later and waking up later than before. Researchers have long known that anxiety and depression can lead to sleeplessness, while sleeping poorly can increase the likelihood of anxiety and depression. But a good night’s rest is also critical for a strong immune system, as well as for health overall. Insufficient sleep over time is associated with a greater risk of diabetes, high blood pressure and heart disease, according to the CDC. It can lead to memory and cognitive issues as well. So how can we get the sleep we need? Here’s how to solve seven common problems that can interfere with your rest and your health. © 1996-2022 The Washington Post

Keyword: Sleep
Link ID: 28303 - Posted: 04.27.2022

Kayt Sukel Each night, as you transition into deep sleep from wakefulness, your body undergoes a remarkable transformation. Your muscles relax. Your breathing slows. Your temperature and blood pressure drop. Even your brain activity changes, decelerating into slow, coordinated waves. Despite these remarkable physiological changes, scientists are now learning that the brain is far from idle during sleep. Rather, it remains hard at work, facilitating memory and learning while uncoupled from the external world. “For a long time, we believed that being awake all day depleted you and that sleep was what was required to restore and reinvigorate the whole body, including the brain,” says Robert Stickgold, a pioneering sleep researcher at Harvard Medical School. “It turns out that rest has very little to do with the function of sleep—rather, our brain is sorting and consolidating the information we learned during the day so we can better access it when it’s needed.” Anyone who has ever pulled an all-nighter knows the effect that sleep deprivation can have on cognitive function, including one’s ability to learn and retain new information. Yet, over the last few decades, neuroscientists across the globe have learned that sleep plays an integral role in memory—and it is a role that is highly conserved across the animal kingdom. To better understand how sleep helps us remember, these researchers have been working to characterize not only the physiological changes observed during sleep, but also the neural mechanisms underlying them. Nearly every animal on earth, from fruit flies to non-human primates, experiences some form of sleep, a naturally recurring state of altered consciousness and inhibited sensory activity. And while the exact amount of time spent in slumber, and the patterns of neural activity, differ from animal to animal, humans are no different. We need sleep to thrive. © 2022 The Dana Foundation.

Keyword: Sleep; Learning & Memory
Link ID: 28285 - Posted: 04.16.2022

Yue Leng Doctors often recommend “power naps” as a way to compensate for a poor night’s sleep and help keep alert until bedtime. But for older adults, extensive power naps could be an early sign of dementia. Research on how napping affects cognition in adults has had mixed results. Some studies on younger adults suggest that napping is beneficial to cognition, while others on older adults suggest it may be linked to cognitive impairment. However, many studies are based on just a single self-reported nap assessment. This methodology may not be accurate for people with cognitive impairment who may not be able to reliably report when or how long they napped. As an epidemiologist who studies sleep and neurodegeneration in older adults, I wanted to find out if changes in napping habits foreshadow other signs of cognitive decline. A study my colleagues and I recently published found that while napping does increase with age, excessive napping may foreshadow cognitive decline. Sleep may play a significant role in Alzheimer’s development. The link between daytime napping and dementia Sleep disturbance and daytime napping are known symptoms of mild to moderate Alzheimer’s disease and other forms of dementia in older adults. They often become more extreme as the disease progresses: Patients are increasingly less likely to fall asleep and more likely to wake up during the night and feel sleepy during the day. © 2010–2022, The Conversation US, Inc.

Keyword: Alzheimers; Sleep
Link ID: 28256 - Posted: 03.30.2022

By Erin Blakemore From the streetlights outside our bedrooms to the lamps and devices inside, sleeping with some amount of light has become a way of life for many. That may not be such a bright idea. Research suggests that sleeping in a moderately lit room could affect metabolic and cardiovascular health compared with snoozing in a room with dimmer light. We don’t need more sleep. We just need more darkness. In a study published in PNAS, researchers at Northwestern University had two groups of 10 young adults sleep in differently lit rooms. One group slept in rooms with dim light for two nights; the other slept one night in a room with dim night and the next in a room with moderate overhead light — about the equivalent of an overcast day. Participants wore heart monitors at night. In the morning, they did a variety of glucose tests. Both groups got the same amount of sleep but their bodies experienced very different nights. Both groups responded well to insulin the first night, when they both slept in dim lighting. On the second night, however, the group sleeping in brighter lighting didn’t respond as well to insulin. The dim light sleepers’ insulin resistance scores fell about 4 percent on the second night, while the bright sleepers’ rose about 15 percent. Their heart rates were faster on the bright night, too. The heightened heart rate and other measures led the researchers to conclude that light activates the sympathetic nervous system, which usually dominates bodily functions during the day.

Keyword: Sleep; Biological Rhythms
Link ID: 28252 - Posted: 03.26.2022

Hannah Devlin Science corespondent Taking long naps could be a precursor of Alzheimer’s disease, according to a study that tracked the daytime sleeping habits of elderly people. The findings could help resolve the conflicting results of the effects of napping on cognition in older adults, with some previous studies highlighting the benefits of a siesta on mood, alertness and performance on mental tasks. The latest study suggests that an increase over time in naps was linked to a higher chance of developing mild cognitive impairment or Alzheimer’s. The scientists think it is more likely that excessive napping could be an early warning sign, rather than it causing mental decline. “It might be a signal of accelerated ageing,” said Dr Yue Leng, an assistant professor of psychiatry at the University of California San Francisco. “The main takeaway is if you didn’t used to take naps and you notice you’re starting to get more sleepy in the day, it might be a signal of declining cognitive health.” The scientists tracked more than 1,000 people, with an average age of 81, over several years. Each year, the participants wore a watch-like device to track mobility for up to 14 days. Each prolonged period of non-activity from 9am to 7pm was interpreted as a nap. The participants also underwent tests to evaluate cognition each year. At the start of the study 76% of participants had no cognitive impairment, 20% had mild cognitive impairment and 4% had Alzheimer’s disease. For participants who did not develop cognitive impairment, daily daytime napping increased by an average 11 minutes a year. The rate of increase doubled after a diagnosis of mild cognitive impairment to a total of 24 minutes and nearly tripled to a total of 68 minutes after a diagnosis of Alzheimer’s disease, according to the research published in the journal Alzheimer’s and dementia. © 2022 Guardian News & Media Limited

Keyword: Alzheimers; Sleep
Link ID: 28244 - Posted: 03.19.2022

By Veronique Greenwood Sharks are celebrated for their apparently ceaseless motion — a small handful of species such as great white sharks must even swim to breathe, keeping water washing over their gills. Still, all that moving doesn’t preclude sharks from having a rest. Sleep across the animal kingdom manifests itself in many peculiar ways, like the birds whose brains sleep one half at a time or the bats that spend almost every hour of their day snoozing. And in a paper published in Current Biology on Wednesday, researchers confirmed that the draughtsboard shark, a small nocturnal shark native to New Zealand, appears to be sleeping during periods of calm, reporting that their metabolism and posture change significantly during these bouts of repose. They do, however, in a creepy touch, keep their eyes open for a lot of it. Further research will be required to demonstrate that other kinds of sharks catch underwater z’s like the draughtsboard shark. But the new study supports the hypothesis that one reason organisms might have evolved sleep is as a tool for conserving energy. Draughtsboard sharks were identified last year as sleepers by this same group of researchers based in New Zealand and Australia. They watched captured sharks carefully in tanks and tested their responses to disturbances during their restful periods. (These sharks are not among those that swim to breathe; they hang out on the ocean floor and pump water over their gills.) The team found that it was more difficult to prompt the sharks into movement if they had been still for a long time, suggesting they were in fact sleeping. This time, said Craig Radford, a professor of marine science at the University of Auckland and an author of the new paper, the researchers were looking to compare the sharks’ metabolisms during these periods of calm, defined as being still for longer than five minutes, with when they were resting for shorter periods and when they were actively swimming. They used a specially built tank with instruments that let them monitor how much oxygen the sharks were using, a way to indirectly measure metabolism. Seven sharks each spent 24 hours in the tank, and the researchers found that these states were indeed quite different. © 2022 The New York Times Company

Keyword: Sleep; Evolution
Link ID: 28234 - Posted: 03.11.2022

ByKelly Servick In 1997, Laura Gould put her 15-month-old daughter, Maria, down for a nap and returned to find her unresponsive. She had died suddenly, with no clues to explain the tragedy besides a fever the night before. When her daughter’s body was sent to the medical examiner’s office, “I thought they’d call me in an hour and tell me what happened … like on TV,” Gould says. Months later, neither that office nor independent pathologists had an explanation. “I hated ending it with ‘the autopsy was inconclusive, go on and live your life now,’” she says. “It just didn’t really feel like that was an option.” Gould co-founded a nonprofit foundation to support grieving parents, raise research funds, and increase awareness of sudden unexplained death in childhood (SUDC), a term used for children older than 12 months. In the United States, roughly 400 deaths fall into this category each year—about one-quarter as many as are labeled sudden infant death syndrome (SIDS). Two recent genetic analyses, one funded in part by Gould’s SUDC Foundation, now suggest potential causes for at least a small fraction of cases: mutations in genes associated with epilepsy, heart arrhythmias, and neurodevelopmental disorders. “Having this data is important,” says Marco Hefti, a neuropathologist at the University of Iowa Carver College of Medicine who was not involved in the new studies. SUDC is not a single disease, but “a grab bag of different things—and the more of those different things you can pull out, the better for everybody.” Neither study can say with certainty that a mutation is responsible for a child’s death. But the findings provide a basis for animal studies that could reveal how the genetic changes interfere with vital functions. They might also inform future child death investigations and potentially even screening programs to prevent deaths. Research on SUDC has lagged that on the more common and better known SIDS. Yet, biologically, SIDS and SUDC “may be part of a spectrum,” says Ingrid Holm, a medical geneticist at Boston Children’s Hospital. In both, death often occurs during sleep, and researchers suspect contributors including undetected heart defects, metabolic disorders, and central nervous system abnormalities. The children who die are roughly 10 times more likely than the average child to have a history of febrile seizures—convulsions that come with fevers in young children, notes neurologist Orrin Devinsky of New York University (NYU) Langone Health. © 2022 American Association for the Advancement of Science.

Keyword: Sleep; Genes & Behavior
Link ID: 28200 - Posted: 02.12.2022