Posts Tagged ‘sleep’

he number of people sleeping in McDonald’s outlets has increased six-fold over the past five years, a trend partly driven by rising rents and substandard housing that makes life especially unbearable in the city’s baking weather, a study has found.

The survey, organised by Junior Chamber International’s Tai Ping Shan branch and conducted in June by volunteers, found 334 people had slept in a McDonald’s outlet nightly over at least the past three months. Of the 110 branches that operate 24 hours in the city, 84 had seen overnight sleepers.

This is a six-fold increase from a similar study in 2013, which found only 57 such people, popularly dubbed McRefugees or McSleepers.

A branch in Tsuen Wan hosted more than 30 sleepers, the highest among all branches, according to the latest study.

Researchers were able to interview 53 McRefugees aged between 19 and 79 in depth, and found 57 per cent of them had a job and 71 per cent of them had flats that they rented or owned, contrary to the common belief that these people tended to be jobless and homeless.

Saving on air conditioning costs, as well as comfort and security, topped a list of reasons given by these interviewees, followed by high rents, conflict with family members, the ability to develop social relations at the chain and substandard housing.

Other reasons included saving on transport costs and time to work, and seeking temporary shelter while waiting for low-rent public housing.

“Family is the basic unit in a society,” Tai Ping Shan publication commission chairwoman Jennifer Hung Sin-yu said. “Even one person who has a home but cannot return is too many. This phenomenon is worth our attention.”

Hung said the reasons given by interviewees showed that unaffordable housing had forced the poor into inferior living conditions such as subdivided flats, which subsequently drove them into McDonald’s for comfort and security.

One McRefugee renting a subdivided flat in To Kwa Wan, Hung said, told volunteers that her landlord charged her HK$16 for a unit of electricity, compared to about HK$1.10 charged by the city’s two main power suppliers.

Hung said the woman’s flat did not have any windows, which made the city’s humid and hot summer even more unbearable without air conditioning.

“She told us sometimes she couldn’t even feel the flow of the air,” Hung said.

Hong Kong is consistently ranked the world’s least affordable property market. As of the end of March, there were 270,000 applicants on the waiting list for public rental housing; the average waiting time for families or single elderly applicants was five years and one month.

Subdivided housing is the main option for these families while they wait, but it is affordable only because of the small sizes – often around 100 sq ft – of these units, which entail fire risks, poor ventilation and poor hygiene.

Besides inadequate housing, family problems are another main issue, Hung said.

One of the cases, a 19-year-old referred to in the study as Ah Lung, was a construction worker who ate, played mobile phone games and slept at a McDonald’s branch in Mong Kok. He did not want to go home due to a bad relationship with his parents, while his income enabled him to live away from home.

A 60-year-old woman was observed by volunteers as “without the unique characteristics of street sleepers”. She was well dressed, with her diamond wedding ring still on her finger. She also had a flat in the New Territories, but had nobody to share the home with her.

She and her late husband did not have any children and she felt lonely in her home and eating by herself, which was why she spent most of her time at the fast-food chain, where there were many people coming and going.

Project consultant Lee Ho-ey said the government should allocate more resources to non-governmental organisations to reach out to McRefugees, providing them with counselling and help.

Thanks to Kebmodee for bringing this to the It’s Interesting community.


By Hilary Hurd Anyaso

Leading theories propose that sleep presents an opportune time for important, new memories to become stabilized. And it’s long been known which brain waves are produced during sleep. But in a new study, researchers set out to better understand the brain mechanisms that secure memory storage.

The team from Northwestern and Princeton universities set out to find more direct and precisely timed evidence for the involvement of one particular sleep wave — known as the “sleep spindle.”

In the study, sleep spindles, described as bursts of brain activity typically lasting around one second, were linked to memory reactivation. The paper, “Sleep spindle refractoriness segregates periods of memory reactivation,” published today in the journal Current Biology.

“The most novel aspect of our study is that we found these spindles occur rhythmically — about every three to six seconds — and this rhythm is related to memory,” said James W. Antony, first author of the study and a postdoctoral fellow in Princeton’s Computational Memory Lab.

Three experiments explored how recent memories are reactivated during sleep. While volunteers took an afternoon nap, sound cues were surreptitiously played. Each was linked to a specific memory. The researchers’ final experiment showed that if cues were presented at opportune times such that spindles could follow them, the linked memories were more likely to be retained. If they were presented when a spindle was unlikely to follow, the linked memories were more likely to be forgotten.

“One particularly remarkable aspect of the study was that we were able to monitor spindles moment by moment while people slept,” said Ken A. Paller, senior author of the study and professor of psychology at Northwestern’s Weinberg College of Arts and Sciences. “Therefore, we could know when the brain was most ready for us to prompt memory reactivation.”
If the researchers reminded people of a recently learned fact, a spindle would likely be evident in the cerebral cortex, and memory for that information would be improved, added Paller, also director of Northwestern’s Cognitive Neuroscience Program.

“In memory research, we know it’s important to segregate experiences while you’re awake so that everything doesn’t just blend together,” said Antony, who worked in Paller’s lab at Northwestern as a doctoral student. “If that happens, you may have difficulty retrieving information because so many things will come to mind at once. We believe the spindle rhythmicity shown here might play a role in segregating successive memory reactivations from each other, preventing overlap that might cause later interference between memories.”

Ultimately, the researchers’ goal is to understand how sleep affects memory under natural conditions and how aging or disease can impact these functions.

“With that goal in mind, we’ve helped elucidate the importance of sleep spindles more generally,” Antony said.

Paller said they are on the trail of the physiology of memory reactivation.

“Future work will be needed to see how spindles fit together with other aspects of the physiology of memory and will involve other types of memory testing and other species,” Paller said.

In addition to Antony and Paller, co-authors are Luis Piloto, Margaret Wang, Paula Pacheco and Kenneth A. Norman, all of Princeton.

The purpose and evolutionary origins of sleep are among the biggest mysteries in neuroscience. Every complex animal, from the humblest fruit fly to the largest blue whale, sleeps — yet scientists can’t explain why any organism would leave itself vulnerable to predators, and unable to eat or mate, for a large portion of the day. Now, researchers have demonstrated for the first time that even an organism without a brain — a kind of jellyfish — shows sleep-like behaviour, suggesting that the origins of sleep are more primitive than thought.

Researchers observed that the rate at which Cassiopea jellyfish pulsed their bell decreased by one-third at night, and the animals were much slower to respond to external stimuli such as food or movement during that time. When deprived of their night-time rest, the jellies were less active the next day.

“Everyone we talk to has an opinion about whether or not jellyfish sleep. It really forces them to grapple with the question of what sleep is,” says Ravi Nath, the paper’s first author and a molecular geneticist at the California Institute of Technology (Caltech) in Pasadena. The study was published in Current Biology.

“This work provides compelling evidence for how early in evolution a sleep-like state evolved,” says Dion Dickman, a neuroscientist at the University of Southern California in Los Angeles.

Mindless sleep
Nath is studying sleep in the worm Caenorhabditis elegans, but whenever he presented his work at research conferences, other scientists scoffed at the idea that such a simple animal could sleep. The question got Nath thinking: how minimal can an animal’s nervous system get before the creature lacks the ability to sleep? Nath’s obsession soon infected his friends and fellow Caltech PhD students Michael Abrams and Claire Bedbrook. Abrams works on jellyfish, and he suggested that one of these creatures would be a suitable model organism, because jellies have neurons but no central nervous system. Instead, their neurons connect in a decentralized neural net.

Cassiopea jellyfish, in particular, caught the trio’s attention. Nicknamed the upside-down jellyfish because of its habit of sitting on the sea floor on its bell, with its tentacles waving upwards, Cassiopea rarely moves on its own. This made it easier for the researchers to design an automated system that used video to track the activity of the pulsing bell. To provide evidence of sleep-like behaviour in Cassiopea (or any other organism), the researchers needed to show a rapidly reversible period of decreased activity, or quiescence, with decreased responsiveness to stimuli. The behaviour also had to be driven by a need to sleep that increased the longer the jellyfish was awake, so that a day of reduced sleep would be followed by increased rest.

Other researchers had already documented a nightly drop in activity in other species of jellyfish, but no jellyfish had been known to display the other aspects of sleep behaviour. In a 35-litre tank, Nath, Abrams and Bedbrook tracked the bell pulses of Cassiopea over six days and nights and found that the rate, which was an average of one pulse per second by day, dropped by almost one-third at night. They also documented night-time pulse-free periods of 10–15 seconds, which didn’t occur during the day.

Restless night
Without an established jellyfish alarm clock, the scientists used a snack of brine shrimp and oyster roe to try to rouse the snoozing Cassiopea. When they dropped food in the tank at night, Cassiopea responded to its treat by returning to a daytime pattern of activity. The team used the jellyfish’s preference for sitting on solid surfaces to test whether quiescent Cassiopea had a delayed response to external stimuli. They slowly lifted the jellyfish off the bottom of the tank using a screen, then pulled it out from under the animal, leaving the jelly floating in the water. It took longer for the creature to begin pulsing and to reorient itself when this happened at night than it did during the day. If the experiment was immediately repeated at night, the jellyfish responded as if it were daytime. Lastly, when the team forced Cassiopea to pull an all-nighter by keeping it awake with repeated pulses of water, they found a 17% drop in activity the following day.

“This work shows that sleep is much older than we thought. The simplicity of these organisms is a door opener to understand why sleep evolved and what it does,” says Thomas Bosch, an evolutionary biologist at Kiel University in Germany. “Sleep can be traced back to these little metazoans — how much further does it go?” he asks.

That’s what Nath, Abrams and Bedbrook want to find out. Amid the chaos of finishing their PhD theses, they have begun searching for ancient genes that might control sleep, in the hope that this might provide hints as to why sleep originally evolved.

You don’t remember it, but you woke up at least 100 times last night. These spontaneous arousals, lasting less than 15 seconds each, occur roughly every five minutes and don’t seem to affect how well-rested you feel. They are unrelated to waking up from a bad dream or your partner tossing and turning. Instead, they seem to be linked to some internal biological mechanism.

Frequently waking up throughout the night may have protected early humans from predators by increasing their awareness of their surroundings during sleep. “The likelihood someone would notice an animal is higher [if they] wake up more often,” says Ronny Bartsch, a senior lecturer in the Department of Physics at Bar-Ilan University in Israel. “When you wake up, you’re more prone to hear things. In deep sleep, you’re completely isolated.”

Sleep scientists, however, have been stumped as to what triggers these nocturnal disruptions. In a new Science Advances paper Bartsch proposes an innovative hypothesis that spontaneous arousals are due to random electrical activity in a specific set of neurons in the brain—aptly named the wake-promoting neurons.

Even when you are asleep your brain cells continuously buzz with a low level of electrical activity akin to white noise on the radio. Occasionally, this electrical clamor reaches a threshold that triggers the firing of neurons. The new paper suggests that when random firing occurs in the wake-promoting neurons, a person briefly jerks awake. But this is countered by a suite of sleep-promoting neurons that helps one quickly fall back to sleep.

Low-level electrical activity in neurons increases in colder temperatures whereas warmer temperatures flatten it. As a result, there should be fewer spontaneous arousals in hot weather. To test this theory, the researchers created computer models that mapped how neuronal noise should act at different temperatures and how the varying electrical activity could affect spontaneous arousals. They also measured sleep in zebra fish, which have similar day/night cycles to humans but are ectothermic, meaning their body temperature is controlled by the environment rather than by internal processes.

The researchers compared the fish’s sleep rates at four different water temperatures: 77, 82 (ideal for zebra fish), 84 and 93 degrees Fahrenheit. Across the board, the colder the water the more often the zebra fish woke up and the longer they stayed awake. The data from the zebra fish and the models of temperature, neuronal noise and arousal matched perfectly. “I think their theory is a perfectly good one and may even be correct,” says Clifford Saper, a neuroscientist at Harvard Medical School’s Division of Sleep Medicine and head of Neurology at Beth Israel Deaconess Medical Center who was not involved with the study. “But the experiment they did doesn’t test that hypothesis.”

The zebra fish experiment shows the fish wake up more frequently and stay awake for longer in colder temperatures but reveals nothing about these animals’ neuronal noise—or humans’, for that matter. Bartsch says that, so far, no studies have figured out how to measure neuronal noise in a sleeping animal.

The idea that warm temperatures cause fewer nocturnal disruptions also seemingly flies in the face of conventional wisdom that a colder bedroom leads to better sleep. But waking up because you are hot and uncomfortable is different from these brief spontaneous arousals. In fact, our bodies are pretty good at regulating their core brain and body temperatures, so the difference of a few degrees outside would not alter neuronal activity. In contrast, zebra fish’s temperature varies quite a bit. Saper says because of this zebra fish “are probably the last animal that I would use to try to make this point.”

Bartsch emphasizes the study is not trying to make a claim about thermoregulation in adults but he says it may have implications for newborn babies. “Because very young infants are more ectothermic than endothermic, their arousability could scale similarly to fish for different ambient temperatures.”

Infants are not as good at regulating their own temperature and so are more vulnerable to changes in the environment. (This is why premature babies have to be kept in incubators.) Consequently, the researchers think newborns may be more susceptible to heat-related fluctuations in neuronal noise.

The theory may have important implications for infant sleep. Although they may be disruptive to parents, spontaneous arousals could help save a baby’s life. Sudden infant death syndrome (SIDS) has been a leading cause of mortality in children between one month and one year of age and yet largely remains a mystery. One idea is that SIDS is caused by a stoppage in breathing, often through accidental suffocation. Waking up during the night can prompt babies to shift or cry out, helping to ensure that they do not have anything obstructing their airways and are still breathing. “We came up again with a theory that the babies with SIDS have low neuronal noise and therefore they have lower arousals,” says Hila Dvir, a physicist at Bar-Ilan. “Because they have low arousals, they are less protected from any hypoxic event—a shortage of oxygen.”

Not everyone is convinced, though. “Over the years, people have come up with ideas to explain SIDS, like a single explanation for it, and they just keep hitting dead ends with it because it’s probably a complex, heterogeneous situation,” says Rafael Pelayo, a clinical professor at the Stanford Center for Sleep Sciences and Medicine “It is a cool idea that this neuronal noise is explaining the arousals. I just think they jumped a little bit when they got into SIDS. It has to be more complicated than that.”

Teenagers and sleep. It’s certainly a passionate subject for many American parents … and those in China. University of Delaware’s Xiaopeng Ji is investigating the relationship between midday-napping behaviors and neurocognitive function in early adolescents. In a study funded by the National Institutes of Health, the School of Nursing assistant professor and principal investigator Jianghong Liu (University of Pennsylvania) turned to the Chinese classroom. With participants from schools in Jintan, she measured midday napping, nighttime sleep duration and sleep quality, and performance on multiple neurocognitive tasks.

Ji is interested in the relationship between sleep and cognition. Because of the intensive learning and education demands, the adolescent population is key. Neurocognitive functioning is essential for learning, emotion and behavior control. Her findings suggest that an association between habitual midday napping and neurocognitive function, especially in China, where midday napping is a cultural practice.

“Daytime napping is quite controversial in the United States. In Western culture, the monophasic sleep pattern is considered a marker of brain maturation,” Ji said. “In China, time for napping is built into the post-lunch schedule for many adults in work settings and students at schools.”

Ji has studied the circadian rhythm of sleep (a person’s 24-hour cycle). A developmental change takes place in circadian rhythm during adolescence; teenagers’ rhythm shifts one to two hours later than the preadolescent period.

“This phase delay is biologically driven in adolescents,” Ji said. “Think about that in a school schedule. Teenagers have to get up early for school. And, with this phase delay of going to bed later, they are at-risk for chronic sleep deprivation.”

Ji explained that these adolescents may experience impaired neurocognitive function, which makes paying attention in school even more difficult. Memory and reasoning ability also suffer.

A circadian dip occurs daily from 12 to 2 p.m. During that period, adolescents are more likely to fall asleep. In a U.S. school, a student does not have a formal opportunity to do so.

“Throughout childhood, U.S. kids experience decreases in napping tendencies. Kids are trained to remove their midday napping behavior,” said Ji. “Conversely in China, the school schedule allows children to maintain it.”

Researchers have taken a friend or foe mentality towards napping. Many consider a midday snooze as needed compensation for nighttime sleep deprivation; another faction believes daytime napping continually interferes with nighttime sleep. Many studies invite people to a lab setting — experimentally imposing the nap — and find the aforementioned cognitive benefits. But Ji said that’s difficult to correlate with habitual sleep at home.

“The results from lab studies may be different from what the population is habitually doing at home — sleeping in their own bed,” Ji said.

Lots of research exists on adults, but that’s not the case for adolescents. This lack of literature motivated Ji to take on the task. And since the American school schedule was a barrier to finding more information, researchers used Chinese data in the University of Delaware and University of Pennsylvania collaborative study.

Key findings

Ji investigated two dimensions of nap behavior — frequency and duration. Routine nappers, who napped five to seven days in a week, had sustained attention, better nonverbal reasoning ability and spatial memory. How long to nap is also an important question? The sweet spot is between 30 to 60 minutes. A nap longer than one hour interferes with circadian rhythm. Participants who slept between 30 to 60 minutes produced better accuracy in attention tasks as well as faster speed. She recommends not to nap after 4 p.m., nor over-nap.

Researchers were surprised to find a positive relationship between midday napping and nighttime sleep, which is different than the literature. Habitual nappers (who napped more often) tended to have a better nighttime sleep.

“That’s different than the findings in the United States, where napping may serve as a function to replace sleep lost from the previous night. Consequently, that may interfere with the following night’s sleep,” Ji said. “In China, a midday nap is considered a healthy lifestyle. Routine nappers are more likely to experience healthy nighttime sleep. So routine nappers are essentially trained to sleep well and sleep more at night.”

Ji was clear that this study was observational. At this point, she cannot conclude causality. She hopes this line of research can inform future studies and public health policy.


People have evolved to sleep much less than chimps, baboons or any other primate studied so far.

A large comparison of primate sleep patterns finds that most species get somewhere between nine and 15 hours of shut-eye daily, while humans average just seven. An analysis of several lifestyle and biological factors, however, predicts people should get 9.55 hours, researchers reported recently in the American Journal of Physical Anthropology. Most other primates in the study typically sleep as much as the scientists’ statistical models predict they should.

Two long-standing features of human life have contributed to unusually short sleep times, argue evolutionary anthropologists Charles Nunn of Duke University and David Samson of the University of Toronto Mississauga. First, when humans’ ancestors descended from the trees to sleep on the ground, individuals probably had to spend more time awake to guard against predator attacks. Second, humans have faced intense pressure to learn and teach new skills and to make social connections at the expense of sleep.

As sleep declined, rapid-eye movement, or REM — sleep linked to learning and memory (SN: 6/11/16, p. 15) — came to play an outsize role in human slumber, the researchers propose. Non-REM sleep accounts for an unexpectedly small share of human sleep, although it may also aid memory (SN: 7/12/14, p. 8), the scientists contend.

“It’s pretty surprising that non-REM sleep time is so low in humans, but something had to give as we slept less,” Nunn says.

Humans may sleep for a surprisingly short time, but Nunn and Samson’s sample of 30 species is too small to reach any firm conclusions, says evolutionary biologist Isabella Capellini of the University of Hull in England. Estimated numbers of primate species often reach 300 or more.

If the findings hold up, Capellini suspects that sleeping for the most part in one major bout per day, rather than in several episodes of varying durations as some primates do, substantially lessened human sleep time.

Nunn and Samson used two statistical models to calculate expected daily amounts of sleep for each species. For 20 of those species, enough data existed to estimate expected amounts of REM and non-REM sleep.

Estimates of all sleep times relied on databases of previous primate sleep findings, largely involving captive animals wearing electrodes that measure brain activity during slumber. To generate predicted sleep values for each primate, the researchers consulted earlier studies of links between sleep patterns and various aspects of primate biology, behavior and environments. For instance, nocturnal animals tend to sleep more than those awake during the day. Species traveling in small groups or inhabiting open habitats along with predators tend to sleep less.

Based on such factors, the researchers predicted humans should sleep an average of 9.55 hours each day. People today sleep an average of seven hours daily, and even less in some small-scale groups (SN: 2/18/17, p. 13). The 36 percent shortfall between predicted and actual sleep is far greater than for any other primate in the study.

Nunn and Samson estimated that people now spend an average of 1.56 hours of snooze time in REM, about as much as the models predict should be spent in that sleep phase. An apparent rise in the proportion of human sleep devoted to REM resulted mainly from a hefty decline in non-REM sleep, the scientists say. By their calculations, people should spend an average of 8.42 hours in non-REM sleep daily, whereas the actual figure reaches only 5.41 hours.

One other primate, South America’s common marmoset (Callithrix jacchus), sleeps less than predicted. Common marmosets sleep an average of 9.5 hours and also exhibit less non-REM sleep than expected. One species sleeps more than predicted: South America’s nocturnal three-striped night monkey (Aotus trivirgatus) catches nearly 17 hours of shut-eye every day. Why these species’ sleep patterns don’t match up with expectations is unclear, Nunn says. Neither monkey departs from predicted sleep patterns to the extent that humans do.

C.L. Nunn and D.R. Samson. Sleep in a comparative context: Investigating how human sleep differs from sleep in other primates. American Journal of Physical Anthropology. Published online February 14, 2018. doi:10.1002/ajpa.23427.

Is your child having a tough time sleeping properly? You may need to keep a check on his/her body mass index (BMI) as a new research suggests that there is a co-relation between the two and can lead to cancer in adulthood.

“Childhood obesity very often leads to adult obesity. This puts them at greater risk of developing obesity-related cancers in adulthood,” said study lead author Bernard Fuemmeler, Professor and Associate Director for Cancer Prevention and Control at the Virginia Commonwealth University.

For the study, researchers enrolled 120 children, with an average age of eight, whose mothers had participated in the Newborn Epigenetic Study both pre-birth and during early childhood.

To track the sleep-wake cycle, the children wore accelerometers continuously for 24 hours a day for a period of at least five days.

They found that shorter sleep duration, measured in hours, was associated with a higher BMI z-score (body mass index adjusted for age and sex).

Each additional hour of sleep was associated with a .13 decrease in BMI z-score and with a 1.29 cm decrease in waist circumference.

More fragmented rest-activity rhythms and increased intradaily variability — a measure of the frequency and extent of transitions between sleep and activity — were also associated with greater waist circumferences.

The study results, to be presented at Obesity and Cancer: Mechanisms Underlying Etiology and Outcomes, indicate that while sleep duration is important, examining markers of sleep quality may also be useful in designing childhood obesity prevention strategies.

“Today, many children are not getting enough sleep. There are a number of distractions, such as screens in the bedroom, that contribute to interrupted, fragmented sleep. This, perpetuated over time, can be a risk factor for obesity,” Fuemmeler said.

“Because of the strong links between obesity and many types of cancer, childhood obesity prevention is cancer prevention.”

Proper sleep in children may prevent cancer later