Researchers Find Possible Missing Link Between Sleep and Improved Memory

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Possible Missing Link Between Sleep and Improved Memory

RIVERSIDE, Calif. (www.ucr.edu) – A team of sleep researchers at the University of California, Riverside, led by psychology professor Sara C. Mednick, has found that the autonomic nervous system, which is responsible for control of bodily functions not consciously directed (such as breathing, heartbeat, and digestive processes) plays a role in promoting memory consolidation – the process of converting information from short-term to long-term memory – during sleep.

The groundbreaking study, “Autonomic Activity During Sleep Predicts Memory Consolidation in Humans,” appears in the journalProceedings of the National Academy of Sciences of the United States of America. Mednick and her team demonstrated, for the first time, that increases in autonomic nervous system (ANS) activity during sleep is correlated with memory improvement.

Read more: https://ucrtoday.ucr.edu/37920

 

Sleep Your Way Out Of Metabolic Disorders

Health care professionals should prescribe better sleep to prevent and treat metabolic disorders

Sweet DreamsEvidence increasingly suggests that insufficient or disturbed sleep is associated with metabolic disorders such as type 2 diabetes and obesity, and addressing poor quality sleep should be a target for the prevention – and even treatment – of these disorders, say the authors [1] of a Review, published in The Lancet Diabetes & Endocrinology journal.

“Metabolic health, in addition to genetic predisposition, is largely dependent on behavioural factors such as dietary habits and physical activity.  In the past few years, sleep loss as a disorder characterising the 24-hour lifestyle of modern societies has increasingly been shown to represent an additional behavioural factor adversely affecting metabolic health,” write the authors.

Addressing some types of sleep disturbance – such as sleep apnoea – may have a directly beneficial effect on patients’ metabolic health, say the authors.  But a far more common problem is people simply not getting enough sleep, particularly due to the increased use of devices such as tablets and portable gaming devices.

Furthermore, disruption of the body’s natural sleeping and waking cycle (circadian desynchrony) often experienced by shift workers and others who work outside daylight hours, also appears to have a clear association with poor metabolic health, accompanied by increased rates of chronic illness and early mortality.

Although a number of epidemiological studies point to a clear association between poor quality sleep and metabolic disorders, until recently, the reason for this association was not clear.  However, experimental studies are starting to provide evidence that there is a direct causal link between loss of sleep and the body’s ability to metabolise glucose, control food intake, and maintain its energy balance.

According to the study authors, “These findings open up new strategies for targeted interventions aimed at the present epidemic of the metabolic syndrome and related diseases. Ongoing and future studies will show whether interventions to improve sleep duration and quality can prevent or even reverse adverse metabolic traits. Meanwhile, on the basis of existing evidence, health care professionals can be safely recommended to motivate their patients to enjoy sufficient sleep at the right time of day.”

[1] The authors of the Review are Dr. Sebastian Schmid, University of Lübeck, Germany; Dr Manfred Hallschmid, University of Tübingen, Germany; and Professor Bernd Schultes, eSwiss Medical and Surgical Centre, St Gallen, Switzerland.

Sleep Deprivation Increases Food Purchasing the Next Day

05 September 2013 Wiley

People who were deprived of one night’s sleep purchased more calories and grams of food in a mock supermarket on the following day in a new study published in the journal Obesity, the official journal of The Obesity Society.

Woman With Sleep DeprevationSleep deprivation also led to increased blood levels of ghrelin, a hormone that increases hunger, on the following morning; however, there was no correlation between individual ghrelin levels and food purchasing, suggesting that other mechanisms-such as impulsive decision making-may be more responsible for increased purchasing.

Researchers in Sweden were curious as to whether sleep deprivation may impair or alter an individual’s food purchasing choices based on its established tendency to impair higher-level thinking and to increase hunger.

“We hypothesized that sleep deprivation’s impact on hunger and decision making would make for the ‘perfect storm’ with regard to shopping and food purchasing-leaving individuals hungrier and less capable of employing self-control and higher-level decision-making processes to avoid making impulsive, calorie-driven purchases,” said first author Colin Chapman, MSc, of Uppsala University.

On the morning after one night of total sleep deprivation, as well as after one night of sleep, Chapman, along with Christian Benedict, PhD, and their colleagues, gave 14 normal-weight men a fixed budget (approximately $50). The men were instructed to purchase as much as they could out of a possible 40 items, including 20 high-caloric foods and 20 low-calorie foods. The prices of the high-caloric foods were then varied to determine if total sleep deprivation affects the flexibility of food purchasing. Before the task, participants received a standardized breakfast to minimize the effect of hunger on their purchases.

Sleep-deprived men purchased significantly

more calories (+9%) and grams (+18%) of food

than they did after one night of sleep.

 

Sleep-deprived men purchased significantly more calories (+9%) and grams (+18%) of food than they did after one night of sleep. The researchers also measured blood levels of ghrelin, finding that the hormone’s concentrations were higher after total sleep deprivation; however, this increase did not correlate with food purchasing behavior.
“Our finding provides a strong rationale for suggesting that patients with concerns regarding caloric intake and weight gain maintain a healthy, normal sleep schedule,” said Chapman.

Follow up studies are needed to address whether these sleep deprivation-induced changes in food purchasing behavior also exist under partial sleep deprivation, though. Additional research should also look into sleep deprivation’s potential impact on purchasing behavior in general, as it may lead to impaired or impulsive purchasing in a variety of other contexts.

Sleep Boosts Production of Brain Support Cells

30 August 2013 Society for Neuroscience (SfN)

 

Animal Study Shows Genes Involved In Brain Repair,

Growth Turned On During Slumber

 

 

Sleep increases the reproduction of the cells that go on to form the insulating material on nerve cell projections in the brain and spinal cord known as myelin, according to an animal study published in the September 4 issue of The Journal of Neuroscience. The findings could one day lead scientists to new insights about sleep’s role in brain repair and growth.

 

Scientists have known for years that many genes are turned on during sleep and off during periods of wakefulness. However, it was unclear how sleep affects specific cells types, such as oligodendrocytes, which make myelin in the healthy brain and in response to injury. Much like the insulation around an electrical wire, myelin allows electrical impulses to move rapidly from one cell to the next.

 

oliogodendrocyteIn the current study, Chiara Cirelli, MD, PhD, and colleagues at the University of Wisconsin, Madison, measured gene activity in oligodendrocytes from mice that slept or were forced to stay awake. The group found that genes promoting myelin formation were turned on during sleep. In contrast, the genes implicated in cell death and the cellular stress response were turned on when the animals stayed awake.

 

“These findings hint at how sleep or lack of sleep might repair or damage the brain,” said Mehdi Tafti, PhD, who studies sleep at the University of Lausanne in Switzerland and was not involved with this study.

 

Additional analysis revealed that the reproduction of oligodendrocyte precursor cells (OPCs) — cells that become oligodendrocytes — doubles during sleep, particularly during rapid eye movement (REM), which is associated with dreaming.

 

“For a long time, sleep researchers focused on how the activity of nerve cells differs when animals are awake versus when they are asleep,” Cirelli said. “Now it is clear that the way other supporting cells in the nervous system operate also changes significantly depending on whether the animal is asleep or awake.”

 

Additionally, Cirelli speculated the findings suggest that extreme and/or chronic sleep loss could possibly aggravate some symptoms of multiple sclerosis (MS), a disease that damages myelin. Cirelli noted that future experiments may examine whether or not an association between sleep patterns and severity of MS symptoms exists.

 

This research was funded by the University of Wisconsin-Madison Department of Psychiatry.

The Journal of Neuroscience is published by the Society for Neuroscience, an organization of more than 42,000 basic scientists and clinicians who study the brain and nervous system. Cirelli can be reached at ccirelli@wisc.edu. More information on myelin and multiple sclerosis can be found on BrainFacts.org.

A Primer For The Perfect Nap

Why Some Snoozing Sessions Leave You Groggy While Others Help

By Sumathi Reddy

Father and Baby Napping

 

There’s an art to napping.

Studies have found different benefits—and detriments—to a nap’s timing, duration and even effect on different people, depending on one’s age and possibly genetics.

“Naps are actually more complicated than we realize,” said David Dinges, a sleep scientist at the University of Pennsylvania’s Perelman School of Medicine.

 

“You have to be deliberative about when you’re going to nap, how long you’re going to nap and if you’re trying to use the nap relative to work or what you have coming up.”

A snooze on the couch on a Sunday afternoon may seem like the perfect way for a responsible adult to unplug. But at a time when roughly one-third of people report not getting enough sleep, more naps, albeit short ones, might make for a more functional workforce, researchers say.

How Long to Nap

Sleep experts break sleep down into several stages, which the brain cycles through roughly every 90 to 120 minutes.

These stages are broadly characterized into non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM is further broken down into stage one and two, which are considered light and intermediate sleep, followed by slow-wave sleep.

Awakening from slow-wave sleep, the deepest kind, results in what doctors call sleep inertia or sleep drunkenness: that groggy feeling that can take awhile to shake off. Finally, there’s REM sleep, often associated with dreaming.

Sara Mednick, an assistant psychology professor at the University of California, Riverside, said the most useful nap depends on what the napper needs.

 

 

  • For a quick boost of alertness, experts say a 10-to-20-minute power nap is adequate for getting back to work in a pinch.
  • For cognitive memory processing, however, a 60-minute nap may do more good, Dr. Mednick said. Including slow-wave sleep helps with remembering facts, places and faces. The downside: some grogginess upon waking.
  • Finally, the 90-minute nap will likely involve a full cycle of sleep, which aids creativity and emotional and procedural memory, such as learning how to ride a bike. Waking up after REM sleep usually means a minimal amount of sleep inertia, Dr. Mednick said.

Experts say the ideal time to nap is generally between the hours of 1 p.m. and 4 p.m. Napping later in the day could interfere with nighttime sleep. Siesta time for many cultures around the world bear out the benefits of a mid day nap.

The body’s circadian rhythms help people to expect to be awake in the morning and early in the night. “So if you take naps when your brain doesn’t expect to be sleeping, you feel kind of thrown off,” contributing to the sleep inertia effect, said Rafael Pelayo, a clinical professor at Stanford University School of Medicine’s Sleep Medicine Center.

A telltale sign of being very sleep-deprived, he said, is dreaming during a short nap. “Definitely in a 20-minute nap you should not be dreaming,” he said.

Ilene Rosen, an associate professor of clinical medicine at Penn’s Perelman School of Medicine, said the ideal duration of a nap is still being debated, but generally speaking the “10-to-20-minute nap is really the optimal time in terms of bang for your buck.”

Sleeping WomanLeon Lack, a psychology professor at Flinders University in Australia, found in a 2006 study in the journal Sleep that among shorter breaks, 10-minute naps packed the most punch.

The study compared naps ranging from 30 seconds to 30 minutes, testing 24 participants at each of several intervals. After each nap the individuals were tested on a variety of mental-processing tasks. The sharpness of the 10-minute nappers became apparent “right away,” Dr. Lack said, and remained apparent for about two to 2 1/2 hours.

Those who took 20- and 30-minute naps tended to feel groggy immediately after the nap for up to about 30 minutes. From there, they showed mental sharpness similar to what researchers saw from the 10-minute nappers, with that sharpness lasting a bit longer.

Jonathan Brandl is a Newton, Mass.-based consultant who works from home. Up at 5 a.m. to hit the gym, he finds himself fading around 2 p.m. His solution is a fast snooze in a comfy chair in his den. His trick for waking up: He holds a pen or pencil in his hand, which usually falls about 10 to 15 minutes into his nap, waking him up.

“After the nap, I feel totally refreshed and then power through the rest of the day,” the 56-year-old Mr. Brandl said.

Though napping at work often remains taboo, experts say growing scientific evidence of its benefits has led select workplaces to accept it.

Christopher Lindholst, chief executive and co-founder of New York-based MetroNaps, has installed specially designed sleeping pods for Google, Huffington Post, an Iowa construction company and the Arizona Diamondbacks baseball team. The chairs retail for $8,995 to $12,985. ( I’m guessing most of us won’t be sleeping in 13K specialty chairs, and most companies will most likely put up with drooling on the desk rather than pop for these high tech sleep aids).

The 60-minute nap may not be kosher in most workplaces, but it also has its pluses.

Man Sleeping at Work on KeyboardIn a 2012 study in the journal Neurobiology of Learning and Memory, researchers split 36 college-aged students into three groups. Each group learned a memory task, pairing words on a screen with a sound. Afterward, one group had 60 minutes to nap, another 10 minutes. The final group didn’t sleep.

Upon retesting, the napping groups fared better, as expected, said Sara Alger, lead author of the study and a postdoctoral research associate at the University of Notre Dame.

More interesting, she noted, was that on further testing, including a week later, the 60-minute group performed far better than the 10-minute group, which now performed as poorly as the non-napping group. The researchers concluded that slow-wave sleep—only experienced by the 60-minute nappers—is necessary for memory consolidation.

Researchers continue to explore why some individuals don’t seem to benefit from naps. Dr. Mednick said ongoing studies are looking at potential genetic differences between habitual and nonhabitual nappers.

 

Sweet DreamsKimberly Cote, a professor of psychology and neuroscience at Brock University in St. Catharines, Ontario, said individuals who don’t normally nap tend to slip into the deep stages of sleep more quickly than those who do. Studies have found through monitoring brain waves that regular nappers are good at maintaining a light sleep when they nap and show better performance improvements than their non-napping counterparts.

“We’re not sure what those individual differences are,” she said, “if that’s something that they’ve learned to do over time or if there’s something biologically different that allows them to nap like that.”

Another trick to waking up perky after a short nap is to drink a cup of coffee before sleeping. Caffeine won’t hurt such a short break and should lessen the effect of sleep inertia.

Dr. Dinges recommends sleeping partially upright to make it easier to wake up. Studies, he said, have found that not lying totally flat results in avoiding falling into a deeper sleep.

“A lot of people say, ‘I only need four hours of sleep a night.’ There’s a few of them around but not very many,” he said.

Write to Sumathi Reddy at sumathi.reddy@wsj.com

A version of this article appeared September 3, 2013, on page D1 in the U.S. edition of The Wall Street Journal, with the headline: A Field Guide to the Perfect Nap.

See Related:

A Good Night’s Sleep Increases Cardiovascular Benefits Of A Healthy Lifestyle

Go Ahead, Hit The Snooze Button

Sleep Disturbances Associated With Work Disability

5 Things You Probably Don’t Know About Sleep — But Should

Extra 30 Minutes Sleep Gives Teens A Boost

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