By Lydia Denworth A remarkably bright pulsing dot has appeared on the monitor in front of us. We are watching, in real time, the brain activity of a graduate student named Nick, who is having an afternoon nap inside an imaging machine at the Massachusetts Institute of Technology, where Lewis has her laboratory. The bright spot first appears toward the bottom of the screen, about where Nick’s throat meets his jaw. It moves slowly upward, fades and then is followed by another bright dot. “It really comes and goes,” says Lewis, who is also affiliated with Massachusetts General Hospital. “It’s in waves.” This moving dot depicts something few people have ever seen: fresh cerebrospinal fluid flowing from the spinal cord into the brain, part of a process that researchers are now learning is vital for keeping us healthy. For decades biologists have pondered a basic problem. As human brains whir and wonder throughout the day, they generate waste—excess proteins and other molecules that can be toxic if not removed. Among those proteins are amyloid beta and tau, key drivers of Alzheimer’s disease. Until recently, it was entirely unclear how the brain takes out this potentially neurotoxic trash. In the rest of the body, garbage removal is handled initially by the lymphatic system. Excess fluid and the waste it carries move from tissue into the spleen, lymph nodes and other parts of the system, where certain particles are removed and put into the bloodstream to be excreted. It was long thought that the brain can’t use the same trick, because the so-called blood-brain barrier, a protective border that keeps infections from reaching critical neural circuitry, stops the transport of most everything in and out. © 2025 SCIENTIFIC AMERICAN,

Keyword: Sleep; Neuroimmunology
Link ID: 29895 - Posted: 08.20.2025

By Andrew Iwaniuk, Georg Striedter Sleep is the most obvious behavior that, in most animals, follows a circadian rhythm. But have you ever seen a bird asleep? Maybe you have, though they usually wake up before you get close enough to see whether they have their eyes closed. Moreover, just because an animal is still and closed its eyes, does that really mean it is sleeping? Maybe it is just resting. Conversely, might some birds sleep with one or both eyes open? Indeed, it is difficult to tell whether an animal is sleeping just by observing it. To overcome this problem, researchers may prod the animal to see whether it is less responsive at certain times of day. A more definitive method for demonstrating sleep in vertebrates is to record an animal’s brain waves (its electroencephalogram, or EEG), because these waves change significantly as an individual falls asleep and then progresses through several stages of sleep. In birds, the use of EEG recordings is essential because they can sleep with one or both eyes open, presumably so they can stay alert to threats. Ostriches, for example, tend to sleep while sitting on the ground, holding their head up high, and keeping both eyes open. They certainly look alert during this time, but EEG waves reveal that they are actually asleep Types and patterns of sleep An EEG measures the activity of many neurons simultaneously. In mammals, it is usually recorded from multiple electrodes placed over the neocortex; in birds, the electrodes are typically placed on top of the hyperpallium (aka the Wulst; see Chapter 1). In addition to performing an EEG, sleep researchers typically record the animal’s eye movements and an electromyogram (EMG), which is a measure of muscle activity, often characterized as muscle “tone.” These kinds of studies have revealed that, in mammals, the transition from the waking state to sleep is marked by a shift from EEG waves that are low in amplitude (i.e., small) and high in frequency (>20 Hz) to waves that are much larger but lower in frequency (1–4 Hz). Because the latter state is characterized by powerful low-frequency EEG waves (aka slow-wave activity), it is commonly called slow-wave sleep (SWS). The mechanisms that cause SWS are complicated and involve a variety of sleep-promoting processes. However, the large amplitude of these slow waves reflects that, during SWS, numerous neurons fire in rhythm with one another so that their electrical potentials sum when they are recorded through the EEG electrodes. © 2025 Simons Foundation

Keyword: Sleep; Evolution
Link ID: 29878 - Posted: 08.06.2025

By Kamal Nahas High-intensity yoga for less than 30 minutes, twice a week, may be the best workout routine for catching high-quality shut-eye, a new study shows. But before people jump on the yoga trend, researchers say more experiments are needed to confirm the study’s findings. While exercise in general is known to improve sleep, a meta-analysis published July 11 in Sleep and Biological Rhythms presents a broad comparison of exercise routines and their influence on sleep quality. By indirectly comparing 30 trials from about a dozen countries, researchers at Harbin Sport University in China ranked how well different exercise methods influence sleep. Yoga won out, followed by walking, resistance training and aerobic exercise. While sleep disorders can be treated with cognitive behavioral therapy or sleeping pills, these interventions don’t work for everyone. “Medications are helpful in the short-term, but some of them have negative effects on the elderly,” says Saurabh Thosar, a sleep researcher at the Oregon Institute of Occupational Health Sciences in Portland. Exercise offers an alternative, but it’s tough to tell which routine is best, making it unclear how best to prescribe it. Trials that investigate this question tend to include one or two types of exercise differing in factors such as how hard, how often or how long they were performed for. Given the global prevalence of sleep problems such as insomnia, which recent estimates say affects about 16 percent of people worldwide, there is a pressing need to find the best exercise to prescribe for a good night’s snooze. © Society for Science & the Public 2000–2025.

Keyword: Sleep
Link ID: 29877 - Posted: 08.06.2025

Katie Kavanagh How does your brain wake up from sleep? A study of more than 1,000 arousals from slumber has revealed precisely how the brain bestirs itself during the transition to alertness1 — a finding that might help to manage sleep inertia, the grogginess that many people feel when hitting the snooze button. Recordings of people as they woke from the dream-laden phase of sleep showed that the first brain regions to rouse are those associated with executive function and decision-making, located at the front of the head. A wave of wakefulness then spreads to the back, ending with an area associated with vision. The findings could change how we think of waking up, says Rachel Rowe, a neuroscientist at the University of Colorado Boulder, who was not involved with the work. The results emphasize that “falling asleep and waking up aren’t simply reverse processes, but really waking up is this ordered wave of activation that moves from the front to the back of the brain”, whereas falling asleep seems to be less linear and more gradual. The study was published today in Current Biology1. The wide-awake brain shows a characteristic pattern of electrical activity, recorded by sensors on the scalp — it looks like a jagged line made up of small, tightly packed peaks and valleys. Although the pattern looks similar during rapid eye movement (REM) sleep, when vivid dreams occur, this stage features a lack of skeletal-muscle movement. The peaks are taller during most stages of non-REM sleep, which ranges from light to very deep slumber. Scientists already knew that the ‘awakened’ signature occurs at different times in different brain regions, but common imaging techniques did not allow these patterns to be explored on a precise timescale. © 2025 Springer Nature Limited

Keyword: Sleep; Attention
Link ID: 29864 - Posted: 07.19.2025

Katie Kavanagh Scientists have identified a group of neurons that might explain the mechanism behind how stress gives rise to problems with sleep and memory. The study — published last week in The Journal of Neuroscience1 — shows that neurons in a brain area called the hypothalamus mediate the effects of stress on sleep and memory, potentially providing a new target for the treatment of stress-related sleep disorders. Previous work has shown that in the hypothalamus, neurons in a structure called the paraventricular nucleus communicate with other areas important for sleep and memory. The neurons of the paraventricular nucleus release a hormone called corticotropin and have a role in regulating stress. But the neural mechanisms underlying the effect of stress on sleep and memory have remained elusive. For co-author Shinjae Chung, a neuroscientist at the University of Pennsylvania in Philadelphia, the question of exactly how stress affects these processes is personal, because, she says, “I experience a lot of sleep problems when I’m stressed”. She adds that “when I have an exam deadline, I have a tendency to have bad sleep that really affects my score the next day”. To study how neurons in the paraventricular nucleus translate stress into sleep and memory problems, the researchers put laboratory mice through a stressful experience by physically restraining the animals in a plastic tube. The team then tested the creatures’ spatial memory and monitored their brain activity as they slept. © 2025 Springer Nature Limited

Keyword: Sleep; Stress
Link ID: 29837 - Posted: 06.21.2025

By Meredith Wadman For people who wear a cumbersome mask to bed to avoid the life-threatening, long-term effects of a serious breathing disease, the prospect of shedding the headgear for a single pill taken at bedtime has been the stuff of dreams. Now, those dreams appear likely to become reality for at least some people with obstructive sleep apnea (OSA), who stop breathing dozens or hundreds of times during the night, causing their blood oxygen to drop before they subconsciously awake. Top-line results from a large clinical trial, released this week, showed a combination of two medications in one pill stimulates muscles that keep the airway open, sharply decreasing breathing disruptions. “It’s pretty clear that this medication combination is reducing obstructive sleep apnea events. And it’s reducing the severity of oxygen drops during sleep. That is exciting,” says Sigrid Veasey, a sleep physician and neuroscientist at the University of Pennsylvania who was not involved with the study. “The effects are robust and have a good scientific basis,” she says. OSA affects an estimated 60 million to 80 million people in the United States, and about 1 billion globally. It comes with long-term risks including stroke, Alzheimer’s disease, and sudden cardiac death. And many people can’t or don’t comply with the gold standard therapy, burdensome continuous positive airway pressure (CPAP) machines that blow air into the throat to keep the airway open, requiring the nocturnal mask. Driven like many before them to search for an alternative, scientists in Boston a decade ago identified a combination of two existing medications that kept the upper airway open by jointly stimulating the relevant muscles, particularly the genioglossus, a workhorse that forms most of the base of the tongue and is critical to keeping the throat open. © 2025 American Association for the Advancement of Science.

Keyword: Sleep
Link ID: 29802 - Posted: 05.24.2025

Freda Kreier Some people can function well on little sleep.Credit: Oleg Breslavtsev/Getty Most people need around eight hours of sleep each night to function, but a rare genetic condition allows some to thrive on as little as three hours. In a study published today in the Proceedings of the National Academy of Sciences1, scientists identified a genetic mutation that probably contributes to some people’s limited sleep needs. Understanding genetic changes in naturally short sleepers — people who sleep for three to six hours every night without negative effects — could help to develop treatments for sleep disorders, says co-author Ying-Hui Fu, a neuroscientist and geneticist at the University of California, San Francisco. “Our bodies continue to work when we go to bed”, detoxifying themselves and repairing damage, she says. “These people, all these functions our bodies are doing while we are sleeping, they can just perform at a higher level than we can.” In the 2000s, Fu and her colleagues were approached by people who slept six hours or less each night. After analysing the genomes of a mother and daughter, the team identified a rare mutation in a gene that helps to regulate humans’ circadian rhythm, the internal clock responsible for our sleep–wake cycle. The researchers suggested that this variation contributed to the duo’s short sleep needs. That discovery prompted others with similar sleeping habits to contact the laboratory for DNA testing. The team now knows several hundred naturally short sleepers. Fu and her colleagues have so far identified five mutations in four genes that can contribute to the trait — although different families tend to have different mutations. Short sleeper In the latest study, the researchers searched for new mutations in the DNA of a naturally short sleeper. They found one in SIK3, a gene encoding an enzyme that, among other things, is active in the space between neurons. Researchers in Japan had previously found another mutation in Sik3 that caused mice to be unusually sleepy2. © 2025 Springer Nature Limited

Keyword: Sleep; Genes & Behavior
Link ID: 29778 - Posted: 05.07.2025

By Giorgia Guglielmi Newly formed memories change over the course of a night’s sleep, a new study in rats suggests. The results reveal that memory processing and consolidation is more complex and prolonged than previously understood, says study investigator Jozsef Csicsvari, professor of systems neuroscience at the Institute of Science and Technology Austria. Sleep has long been known to help consolidate memories, though most studies have tracked only a few hours of this process. The new work monitored memory-related brain activity patterns across almost an entire day—representing a significant step forward, says Lisa Genzel, associate professor of neuroscience at Radboud University, who wasn’t involved in the research. That’s “a heroic effort,” she says. Csicsvari and his team implanted wireless electrodes into the hippocampus of three rats and recorded neuronal activity as the animals learned to navigate a maze in search of hidden pieces of food, rested or slept for 16 to 20 hours after, and then revisited the same food locations the following day. The neurons that fired during learning became active again throughout the rest period, especially during sleep, the team found. This reactivation is a key part of memory consolidation, and it doesn’t just happen immediately after learning; instead, it continues for hours, the study shows. And while the animals slept, their brain activity patterns gradually shifted to resemble the post-sleep recall patterns—a change known as “representational drift” that likely helps the brain weave new information into what it already knows, Csicsvari says. Some neuron groups may be more involved than others in updating memories, the work showed. Some cell types remained stable, whereas others changed their activity. For example, hippocampal neurons called CA1 pyramidal cells showed distinct firing patterns during memory reactivation. And interneurons, too, appeared to play a supporting role, mirroring the changes in pyramidal cells. The team published their findings in Neuron in March. © 2025 Simons Foundation

Keyword: Sleep; Learning & Memory
Link ID: 29777 - Posted: 05.07.2025

By Lydia Denworth The rattling or whistling noises of regular snorers are famously hard on those who share their beds. Middle-aged men and people who are overweight come frequently to mind as perpetrators because they are the most common sufferers of sleep apnea, often caused by a temporarily collapsing airway that makes the person snore heavily. But recent studies in children and pregnant women have revealed that even mild snoring can negatively affect health, behavior and quality of life. “We know that disordered breathing and disturbed sleep can have myriad physiological effects,” says Susan Redline, a pulmonologist and epidemiologist at Brigham and Women’s Hospital in Boston. “More people have sleep-disordered breathing than have overt apneas. We shouldn’t forget about them.” Almost everyone snores occasionally. Allergies and respiratory infections can trigger it. When the upper airway at the back of the throat narrows, it causes the tissues there to vibrate, creating the familiar rumble. Physicians worry if people habitually snore three or more nights a week, especially if they have other red flags such as unexplained high blood pressure. The category of sleep-disordered breathing includes apnea’s total pause in breathing, shallow breaths called hypopnea, snoring without apneas, and a subtler problem called flow limitation in which the shape of the airway is narrowed but the sleeper makes no noise. The standard measure of severity is the apnea-hypopnea index (AHI), which counts pauses in breathing per hour and associated drops in oxygen levels. The normal level in adults is fewer than five pauses; more than 30 is severe. In children, 10 pauses could be considered moderately severe. © 2025 SCIENTIFIC AMERICAN,

Keyword: Sleep; Development of the Brain
Link ID: 29764 - Posted: 04.30.2025

By Michael Schulson Two years ago, at a Stop & Shop in Rhode Island, the Danish neuroscientist and physician Henriette Edemann-Callesen visited an aisle stocked with sleep aids containing melatonin. She looked around in amazement. Then she took out her phone and snapped a photo to send to colleagues back home. “It was really pretty astonishing,” she recalled recently. In Denmark, as in many countries, the hormone melatonin is a prescription drug for treating sleep problems, mostly in adults. Doctors are supposed to prescribe it to children only if they have certain developmental disorders that make it difficult to sleep — and only after the family has tried other methods to address the problem. But at the Rhode Island Stop & Shop, melatonin was available over the counter, as a dietary supplement, meaning it receives slightly less regulatory scrutiny, in some respects, than a package of Skittles. Many of the products were marketed for children, in colorful bottles filled with liquid drops and chewable tablets and bright gummies that look and taste like candy. A quiet but profound shift is underway in American parenting, as more and more caregivers turn to pharmacological solutions to help children sleep. What makes that shift unusual is that it’s largely taking place outside the traditional boundaries of health care. Instead, it’s driven by the country’s sprawling dietary supplements industry, which critics have long said has little regulatory oversight — and which may get a boost from Secretary of Health and Human Services Robert F. Kennedy Jr., who is widely seen as an ally to supplement makers. Thirty years ago, few people were giving melatonin to children, outside of a handful of controlled experiments. Even as melatonin supplements grew in popularity among adults in the late 1990s in the United States and Canada, some of those products carried strict warnings not to give them to younger people. But with time, the age floor dropped, and by the mid-2000s, news reports and academic surveys suggest some early adopters were doing just that. (Try it for ages 11-and-up only, one CNN report warned at the time.) By 2013, according to a Wall Street Journal article, a handful of companies were marketing melatonin products specifically for kids.

Keyword: Biological Rhythms; Development of the Brain
Link ID: 29740 - Posted: 04.12.2025

By Veronique Greenwood Encased in the skull, perched atop the spine, the brain has a carefully managed existence. It receives only certain nutrients, filtered through the blood-brain barrier; an elaborate system of protective membranes surrounds it. That privileged space contains a mystery. For more than a century, scientists have wondered: If it’s so hard for anything to get into the brain, how does waste get out? The brain has one of the highest metabolisms of any organ in the body, and that process must yield by-products that need to be removed. In the rest of the body, blood vessels are shadowed by a system of lymphatic vessels. Molecules that have served their purpose in the blood move into these fluid-filled tubes and are swept away to the lymph nodes for processing. But blood vessels in the brain have no such outlet. Several hundred kilometers of them, all told, seem to thread their way through this dense, busily working tissue without a matching waste system. However, the brain’s blood vessels are surrounded by open, fluid-filled spaces. In recent decades, the cerebrospinal fluid, or CSF, in those spaces has drawn a great deal of interest. “Maybe the CSF can be a highway, in a way, for the flow or exchange of different things within the brain,” said Steven Proulx, who studies the CSF system at the University of Bern. A recent paper in Cell contains a new report about what is going on around the brain (opens a new tab) and in its hidden cavities. A team at the University of Rochester led by the neurologist Maiken Nedergaard (opens a new tab) asked whether the slow pumping of the brain’s blood vessels might be able to push the fluid around, among, and in some cases through cells, to potentially drive a system of drainage. In a mouse model, researchers injected a glowing dye into CSF, manipulated the blood vessel walls to trigger a pumping action, and saw the dye concentration increase in the brain soon after. They concluded that the movement of blood vessels might be enough to move CSF, and possibly the brain’s waste, over long distances. © 2025 Simons Foundation.

Keyword: Brain imaging; Sleep
Link ID: 29722 - Posted: 03.27.2025

By Laura Sanders So many of us struggle to fall asleep and stay there through the night. About a third of U.S. adults aren’t sleeping enough. Teenagers’ sleep is even worse; 8 in 10 teens are sleep deprived. Our collective exhaustion isn’t good for us. Lack of sleep can come with a range of health problems. Our immune systems, hormones, hearts — maybe all the body’s major systems — are influenced by sleep. In the brain, our memory, creativity and ability to learn are, too. But for something that’s so entwined with our health, the actual jobs of sleep are still, in many ways, a mystery. Scientists have tons of ideas: Perhaps sleep is for rifling through memories, picking out the important ones. Or maybe it’s a quiet, still time for growing bones in children. Or maybe it’s a time to let the brain loose on whatever problem vexed you that day. (One delightfully myopic theory posits that sleep, especially the rapid eye movement stage, is for squeezing fluid around the eye to keep it lubricated.) Figuring out why we sleep has puzzled scientists for as long as the question has existed. It’s like following hundreds of disappearing breadcrumbs on paths through a forest of trees that keep shifting spots, only to realize you’re standing alone in only your underwear. Oh, and you forgot to study for the test. Given this hazy scientific landscape, it’s no surprise that efforts to help the sleep-deprived catch some z’s might fall short or have unintended consequences. That’s clear from a new study of the sleep medicine zolpidem. Zolpidem, sold as Ambien, messes with yet another possible job of sleep – housekeeping. © Society for Science & the Public 2000–2025

Keyword: Sleep
Link ID: 29663 - Posted: 02.08.2025

By Mitch Leslie Scientists think sleep is the brain’s rinse cycle, when fluid percolating through the organ flushes out chemical waste that accumulated while we were awake. But what propels this circulation has been uncertain. A study of mice, reported today in Cell, suggests regular contractions of blood vessels in the brain, stimulated by the periodic release of a chemical cousin of adrenaline, push the fluid along. “This is excellent science,” says neuroscientist Suzana Herculano-Houzel of Vanderbilt University, who wasn’t connected to the study. “They put a number of pieces of evidence together that tell a pretty compelling story.” The scientists also found that the sleep drug zolpidem, better known as Ambien, impedes the blood vessel oscillations and the fluid flow they promote, implying it could hamper cleansing. The finding could help researchers create new sleep aids that preserve this brain-scrubbing function. The brain lacks the lymphatic vessels that collect and move fluid in other parts of the body. But in 2012, neuroscientist Maiken Nedergaard of the University of Rochester Medical Center and colleagues identified an alternative drainage system in which cerebrospinal fluid, the liquid bathing the brain, seeps through the organ via tiny passages alongside blood vessels, sweeping away metabolic refuse and other unwanted molecules. Fluid flow through this so-called glymphatic system ramps up during sleep, they also reported. Studies from 
Nedergaard’s group and others suggest vigorous glymphatic clearance is beneficial: Circulation falters in Alzheimer’s disease and other neurodegenerative illnesses. Some researchers have challenged parts of this picture, however; a 2024 study, for example, suggested waste clearance is actually faster during waking than during sleep. In the new research, Nedergaard and her team wanted to pin down what keeps cerebrospinal fluid moving through the brain. But studying the mouse glymphatic system often involves anesthetizing the rodents, she says, which is very different from natural sleep. To avoid this problem, the scientists surgically implanted mice with electrodes and fiber optic filaments. Although the rodents are tethered to a set of cables, they can fall asleep normally while researchers track blood volume, electrical activity, and chemical levels and use light transmitted through the fiber optic lines to activate certain groups of neurons.

Keyword: Sleep
Link ID: 29626 - Posted: 01.11.2025

By Traci Watson New clues have emerged in the mystery of how the brain avoids ‘catastrophic forgetting’ — the distortion and overwriting of previously established memories when new ones are created. A research team has found that, at least in mice, the brain processes new and old memories in separate phases of sleep, which might prevent mixing between the two. Assuming that the finding is confirmed in other animals, “I put all my money that this segregation will also occur in humans”, says György Buzsáki, a systems neuroscientist at New York University in New York City. That’s because memory is an evolutionarily ancient system, says Buzsáki, who was not part of the research team but once supervised the work of some of its members. The work was published on Wednesday in Nature1. Scientists have long known that, during sleep, the brain ‘replays’ recent experiences: the same neurons involved in an experience fire in the same order. This mechanism helps to solidify the experience as a memory and prepare it for long-term storage. To study brain function during sleep, the research team exploited a quirk of mice: their eyes are partially open during some stages of slumber. The team monitored one eye in each mouse as it slept. During a deep phase of sleep, the researchers observed the pupils shrink and then return to their original, larger size repeatedly, with each cycle lasting roughly one minute. Neuron recordings showed that most of the brain’s replay of experiences took place when the animals’ pupils were small. That led the scientists to wonder whether pupil size and memory processing are linked. To find out, they enlisted a technique called optogenetics, which uses light to either trigger or suppress the electrical activity of genetically engineered neurons in the brain. First, they trained engineered mice to find a sweet treat hidden on a platform. Immediately after these lessons, as the mice slept, the authors used optogenetics to reduce bursts of neuronal firing that have been linked to replay. They did so during both the small-pupil and large-pupil stages of sleep. © 2025 Springer Nature Limited

Keyword: Learning & Memory; Sleep
Link ID: 29615 - Posted: 01.04.2025

By Marla Broadfoot Everyone has heard that it’s vital to get seven to nine hours of sleep a night, a recommendation repeated so often it has become gospel. Get anything less, and you are more likely to suffer from poor health in the short and long term — memory problems, metabolic issues, depression, dementia, heart disease, a weakened immune system. But in recent years, scientists have discovered a rare breed who consistently get little shut-eye and are no worse for wear. Natural short sleepers, as they are called, are genetically wired to need only four to six hours of sleep a night. These outliers suggest that quality, not quantity, is what matters. If scientists could figure out what these people do differently it might, they hope, provide insight into sleep’s very nature. “The bottom line is, we don’t understand what sleep is, let alone what it’s for. That’s pretty incredible, given that the average person sleeps a third of their lives,” says Louis Ptáček, a neurologist at the University of California San Francisco. Scientists once thought sleep was little more than a period of rest, like powering down a computer in preparation for the next day’s work. Thomas Edison called sleep a waste of time — “a heritage from our cave days” — and claimed to never sleep more than four hours a night. His invention of the incandescent lightbulb encouraged shorter sleep times in others. Today, a historically high number of US adults are sleeping less than five hours a night. But modern sleep research has shown that sleep is an active, complicated process we don’t necessarily want to cut short. During sleep, scientists suspect that our bodies and brains are replenishing energy stores, flushing waste and toxins, pruning synapses and consolidating memories. As a result, chronic sleep deprivation can have serious health consequences.

Keyword: Sleep; Genes & Behavior
Link ID: 29603 - Posted: 12.14.2024

By Derek Thompson At 3 a.m. I’m jolted awake. The room is dark and still. I grab my phone and scan sports scores and Twitter. Still awake. A faceless physician whispers in my mind: To overcome middle-of-the-night insomnia, experts say you ought to get out of bed … I get out of bed. I pour a glass of water and drink it. I go back to bed. Still awake. Perhaps you know the feeling. Like millions of Americans and hundreds of millions of people around the world, I suffer from so-called mid-sleep awakenings that can keep me up for hours. One day, I was researching my nocturnal issues when I discovered a cottage industry of writers and sleep hackers who claim that sleep is a nightmare because of the industrial revolution, of all things. Essays in The Guardian, CNN, The New York Times, and The New York Times Magazine recommended an old fix for restlessness called “segmented sleep.” In premodern Europe, and perhaps centuries earlier, people routinely went to sleep around nightfall and woke up around midnight—only to go back to sleep a few hours later, until morning. They slept sort of like I do, but they were Zen about it. Then, the hackers claim, modernity came along and ruined everything by pressuring everybody to sleep in one big chunk. The romanticization of preindustrial sleep fascinated me. It also snapped into a popular template of contemporary internet analysis: If you experience a moment’s unpleasantness, first blame modern capitalism. So I reached out to Roger Ekirch, the historian whose work broke open the field of segmented sleep more than 20 years ago. In the 1980s, Ekirch was researching a book about nighttime before the industrial revolution. One day in London, wading through public records, he stumbled on references to “first sleep” and “second sleep” in a crime report from the 1600s. He had never seen the phrases before. When he broadened his search, he found mentions of first sleep in Italian (primo sonno), French (premier sommeil), and even Latin (primo somno); he found documentation in Africa, the Middle East, South Asia, and Latin America. © 2024 The Atlantic Monthly Group.

Keyword: Sleep
Link ID: 29595 - Posted: 12.11.2024

Andrew Gregory Health editor Failing to stick to a regular time for going to bed and waking up increases the risk of stroke, heart attack and heart failure by 26%, even for those who get a full night’s sleep, the most comprehensive study of its kind suggests. Previous studies have focused on the links between sleep duration and health outcomes, with people advised to get between seven and nine hours shut-eye a night. That advice still stands. But researchers are increasingly focusing on sleep patterns, and in particular the impact of irregular sleep – defined as variations in the time a person goes to sleep and wakes up. The new study found irregular sleep – going to bed and waking up at different times each day – was “strongly associated” with a higher risk of major adverse cardiovascular events. Even getting eight hours of sleep was insufficient to offset the harmful effects of consistently varying bed and wake-up times, experts said. The research, published in the Journal of Epidemiology and Community Health, involved 72,269 people aged 40 to 79 from the UK Biobank study. It did not establish precisely how close you have to get to the same bed and wake-up time – only that the further away you are, the higher the risk of harm. The lead author, Jean-Philippe Chaput, of the University of Ottawa, said: “We should aim to wake up and go to sleep within 30 minutes of the same time each night and each morning, including weekends. Within an hour of the same time is good but less good than 30 minutes, and even better is to have zero variation. “Beyond an hour’s difference each night and each morning means irregular sleep. That can have negative health impacts. The closer you are to zero variation the better. “No one is perfect across a whole year, and if you don’t have a regular sleep pattern for one or two days a week, it’s not going to kill you. But if you repeatedly have irregular sleep, five or six days a week, then it becomes chronic, and that is a problem.” Chaput said waking up at the same time each day was more important than going to bed at the same time. “Waking up at different times each morning really messes with your internal clock, and that can have adverse health consequences,” he said. © 2024 Guardian News & Media Limited

Keyword: Sleep
Link ID: 29578 - Posted: 11.27.2024

By Shaena Montanari In the Sterling Hall of Medicine at Yale University, a sign on a walk-in refrigerator door tells people to keep their voices down. Inside, about 250 ground squirrels are hibernating, each surrounded by shredded paper fluff and curled up in a clear plastic box. Shelves lined with these makeshift nests are bathed in red light that only the researchers can see, leaving the motionless animals in complete darkness. From about September to April—roughly the hibernation season for these thirteen-lined ground squirrels, which have stripes reminiscent of a chipmunk—the temperature inside the homemade hibernaculum is set at 4 degrees Celsius. The tiny rodents’ body temperature is the same as the chilly air, and their breathing and heart rates slow to just a handful of breaths and beats per minute—an energy-conserving response known as torpor. Scientists have studied this extreme physiological state for more than a century, says Elena Gracheva, whose bustling lab sits just outside the silent hibernaculum. But to date, they have focused mainly on physiological changes in individual peripheral organs that help an animal survive in cold temperatures. It is still unknown how the central nervous system regulates the process, she says. “We know a lot about physiology, but we don’t know the molecular basis.” Gracheva, professor of physiology and neuroscience at Yale University, is part of a small cadre of scientists who have set their sights on revealing those neural hibernation controls, using advanced tools to explore how the brain and other organ systems work together to maintain homeostasis. Their efforts are opening a “new era” in hibernation research, says Shona Wood, associate professor of Arctic chronobiology and physiology at the Arctic University of Norway. © 2024 Simons Foundation

Keyword: Sleep
Link ID: 29550 - Posted: 11.09.2024

By Lynne Peeples Living things began tracking the incremental passage of time long before the human-made clock lent its hands. As life grew in harmony with the sun’s daily march through the sky, and with the seasons, phases of the moon, tides, and other predictable environmental cycles, evolution ingrained biology with the timekeeping tools to keep a step ahead. It gifted an ability to anticipate changes, rather than respond to them, and an internal nudge to do things when most advantageous and to avoid doing things when not so advantageous. Of course, that optimal timing depended on a species’ niche on the 24-hour clock. When mammals first arose, for example, they were nocturnal — most active during the hours that the dinosaurs slept. Now mammals occupy both their choice territories on a spinning planet and their preferred space on a rotating clock. Timing is everything when it comes to seeking and digesting food, storing food, avoiding becoming food, dodging exposure to DNA-damaging ultraviolet radiation, and many more vital activities, such as navigating, migrating, and reproducing. Take the Eudyptula minor, a tiny penguin species that lives on Phillip Island in Australia. The slate-blue plumaged seabird speed waddles from the ocean to burrow home at the same “sun time” each day — just after sunset. Finding that precise window between day and night maximizes the penguins’ fishing time, allows them enough light to see their way to their burrows, and minimizes the chances they become visible food along the way for nighttime predators, such as orcas, seabirds, and feral cats. An internal clock off by just 10 minutes could prove fatal, one source told me. The island’s tourism industry capitalizes on this predictable “Penguin Parade.” A website lists approximate penguin arrival times for every month of the year and sells tickets to witness the spectacle. A higher ticket price grants visitors access to an underground viewing structure where they can watch the procession of waddlers at eye level. In October 2022, lucky visitors got to view a record-breaking 5,440 little penguins storm the shore and hurry home.

Keyword: Biological Rhythms
Link ID: 29549 - Posted: 11.09.2024

By Mariana Lenharo Immune cells rush to the brain and promote deep sleep after a heart attack, according to a new study1 involving both mice and humans. This heavy slumber helps recovery by easing inflammation in the heart, the study found. The findings, published today in Nature, could help to guide care for people after a heart attack, says co-author Cameron McAlpine at the Icahn School of Medicine at Mount Sinai in New York City, who studies immune function in the cardiovascular and nervous systems. “Getting sufficient sleep and rest after a heart attack is important for long-term healing of the heart,” he notes. The implications of the study go beyond heart attack, says Rachel Rowe, a specialist in sleep and inflammation at the University of Colorado Boulder. “For any kind of injury, your body’s natural response would be to help you sleep so your body can heal,” she says. Scientists have long known that sleep and cardiovascular health are linked. People who sleep poorly are at a higher risk of developing high blood pressure, for example, than are sound sleepers. But how cardiovascular disease affects sleep has been less explored. To learn more, the authors induced heart attacks in mice and investigated the animals’ brainwaves. The researchers found that these mice spent much more time in slow-wave sleep — a stage of deep sleep that has been associated with healing — than did mice that hadn’t had a heart attack. Next, the authors sought to understand what was causing that effect. One obvious place to look was the brain, which controls sleep, notes McAlpine. After a heart attack, immune cells trigger a massive burst of inflammation in the heart, he says, and the researchers wondered whether these immune changes also occurred in the brain. © 2024 Springer Nature Limited

Keyword: Sleep
Link ID: 29542 - Posted: 11.06.2024