Tag: sleep

Prompts During Sleep Boosts Recall of Names and Faces

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Hearing names repeated during deep sleep may help bolster recall of names and faces, according to new research from Northwestern University.

The researchers found that people’s name recall improved significantly when memories of newly learned face-name associations were reactivated while they were napping. Uninterrupted deep sleep was key in this improvement.

“It’s a new and exciting finding about sleep, because it tells us that the way information is reactivated during sleep to improve memory storage is linked with high-quality sleep,” said lead author Nathan Whitmore, a PhD candidate in the Interdepartmental Neuroscience Program at Northwestern University.

The research is reported in the Nature partner journal npj Science of Learning.

The three main stages of the experiment of Whitmore et al. (2022). First, participants learned 80 face-name associations. Next, they slept while EEG was monitored to determine sleep stage, and 20 of the spoken names were presented softly over background music during slow-wave sleep. Finally, memory testing showed superior memory due to memory reactivation during sleep, but only when sleep was undisturbed by sound presentations. Credit: Nathan Whitmore, a Ph.D. candidate in the Interdepartmental Neuroscience Program at Northwestern University.

The results also highlighted the importance of adequate sleep: for study participants with EEG measurements that indicated disrupted sleep, the memory reactivation had no effect and may even be detrimental. But in those with uninterrupted sleep during the specific times of sound presentations, the reactivation helped participants recall just over 1.5 more names.

The study recruited 24 participants, aged 18-31 years old, who were asked to memorise the faces and names of 40 pupils from a hypothetical Latin American history class and another 40 from a Japanese history class. When each face was presented again, they were asked to recall the associated name. After the learning exercise, participants took a nap while the researchers carefully monitored brain activity using EEG measurements. When participants reached the N3 “deep sleep” state, some of the names were softly played on a speaker with music that was associated with one of the classes.

When participants awoke, they were again tested on recognising faces and recalling their names.

According to the researchers, the finding on the relationship between sleep disruption and memory accuracy is noteworthy for several reasons.

“We already know that some sleep disorders like apnoea can impair memory,” said Whitmore. “Our research suggests a potential explanation for this—frequent sleep interruptions at night might be degrading memory.”

The lab is currently exploring the reactivation of memories and deliberately disrupting sleep in order to learn more about the relevant brain mechanisms.

Source: EurekAlert!

Melatonin May be The Culprit for Nocturnal Asthma

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Why patients with asthma find their condition worsens at night has remained largely unknown, but now researchers have found that the sleep hormone melatonin may be the culprit.

In ‘nocturnal asthma’ , patients with asthma often experience a worsening of asthmatic symptoms at night. More than 50% of asthma deaths occur at night, showing a link between nocturnal asthma symptoms and asthma deaths. Though numerous triggers that explain the pathogenesis of nocturnal asthma have been described, the precise mechanisms regulating this asthma phenotype remain obscured until now. Now, a study published in the American Journal of Physiology Lung Cellular and Molecular Physiology may have explained the relationship via melatonin.

Asthma patients suffer from bronchoconstriction which may be eased with a bronchodilator. However, melatonin, which is often prescribed for insomnia, favours a state of bronchoconstriction and weakens the relaxing effect of a bronchodilator through the activation of the melatonin MT2 receptor.

To elucidate this, the research group identified the expression of the melatonin MT2 receptor in human airway smooth muscle. They observed that the activation of the melatonin MT2 receptor with higher doses of melatonin or melatonin receptor agonist ramelteon greatly potentiated the bronchoconstriction. In addition, melatonin attenuated the relaxing effects of the widely used bronchodilator β-adrenoceptor agonist.

“Although serum concentration of melatonin did not significantly induce the airway constriction, greater doses of melatonin, which is clinically used to treat insomnia, jet lag, or cancer, worsened asthma symptoms and impaired the therapeutic effect of bronchodilators,” said study leader Kentaro Mizuta from Tohoku University Graduate School of Dentistry .

First author Haruka Sasaki added, “The pharmacological therapy that blocks the melatonin MT2 receptor could inhibit the detrimental effects of melatonin on airways.”

Source: Tohoku University

Alcohol Triggers AF – But Not Caffeine or Other Likely Culprits

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Researchers have found that, out of possible triggers they tested, only alcohol use was consistently associated with more episodes of atrial fibrillation (AF). The study, published in JAMA Cardiologydid not find that the other triggers, caffeine, sleep deprivation and sleeping on the left side, to be associated with the common heart condition.

A surprising finding was that, although most of the things that participants thought to be related to their AF were not, those in the intervention group still had less arrhythmia than the people in a non self-monitoring control group.

“This suggests that those personalised assessments revealed actionable results,” said lead author Gregory Marcus, MD, MAS, professor at University of California, San Francisco. “Although caffeine was the most commonly selected trigger for testing, we found no evidence of a near-term relationship between caffeine consumption and atrial fibrillation. In contrast, alcohol consumption most consistently exhibited heightened risks of atrial fibrillation.”

Although caffeine was the most commonly selected trigger for testing, we found no evidence of a near-term relationship between caffeine consumption and atrial fibrillation.

In a brainstorming session, patients had said researching individual triggers for AF was their top priority, giving rise to the I-STOP-AFib study, which enabled individuals to test any presumed AF trigger. About 450 people participated, 58% male and 92% white.

Participants used a mobile electrocardiogram recording device along with a phone app to log potential triggers like drinking alcohol and caffeine, sleeping on the left side or not getting enough sleep, eating a large meal, a cold drink, or sticking to a particular diet, engaging in exercise, or anything else they thought was relevant to their AF. While participants were most likely to select caffeine as a trigger, there was no association with AF. Recent research has similarly failed to show a link between caffeine and arrhythmias – on the contrary, investigators found it may have a protective effect.

The new study demonstrated that consumption of alcohol was the only trigger that consistently resulted in significantly more self-reported AF episodes.

The individualised ‘n-of-1’ testing method did not validate participant-selected triggers for AF. But trial participants did report fewer AF episodes than those in the control group, and the data suggest that behaviours like avoiding alcohol could lessen the chances of having an AF episode.
“This completely remote, siteless, mobile-app based study will hopefully pave the way for many investigators and patients to conduct similar personalised ‘n-of-1’ experiments that can provide clinically relevant information specific to the individual,” said Prof Marcus.

Source: University of California, San Francisco

A Daily Dose of Sunshine Improves Mood and Sleep Quality

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Getting a daily dose of sunlight can improve a person’s mood and sleep quality, a new study has found.

A research team led by Monash University PhD student Angus Burns and Associate Professor Sean Cain conducted a study published in the upcoming December issue of the Journal of Affective Disorders.

The study examined 400 000 participants in the UK Biobank programme, and found that a lack of daytime light exposure was a risk factor for depressive symptoms, poor mood, and insomnia.

Burns said that most light and health-related messaging focusses on avoiding light at night, as it disrupts the circadian rhythm, but this study highlights the importance of getting enough daylight to ensure our bodies function optimally.

“In this study, we observed that the greater time spent in outdoor light during the day was associated with fewer depressive symptoms, lower odds of using antidepressant medication, better sleep and fewer symptoms of insomnia,” Burns said.

“These results may be explained by the impacts of light on the circadian system and the direct effects of light on mood centres in the brain.”

Associate Professor Cain said a few small changes to a person’s daily routine could help improve their mood, sleep, and energy levels.

“People now spend most waking hours in intermediate, artificial lighting conditions, due to reduced sunlight exposure and relatively bright night-time light exposure,” he said.

“In this study, we observed that greater time spent in outdoor light was associated with better mood outcomes, better quality sleep, and ease of wakening.

“Insufficient exposure to daytime light could be a key factor contributing to poor mood and sleep outcomes in depressive disorders. My general advice for everyone is simple: when the sun is out, get as much light as you can, but after it sets, keep it dark. Your body will thank you.”

Source: Monash University

Study Links Poor Sleep to Arrhythmias

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A large observational study linked poor sleep to arrhythmias, although genetic risk factors for rhythm problems appeared to lessen the association.

The results, published in the American College of Cardiology, show that best self-reported sleeps (getting 7-8 hours etc) had a 29% lower risk of developing atrial fibrillation or flutter and a 35% lower risk of bradyarrhythmia compared with those with the worst sleep patterns (eg, being a night owl, sleeping too little, snoring, and having insomnia or daytime drowsiness).

The ventricular arrhythmia risk fell away after demographic, lifestyle, and genetic risk factors were accounted for.

Together with previous research linking a healthy sleep pattern to reduced cardiovascular disease and heart failure risks, the findings, according to the researchers, “emphasise the importance of improving the overall sleep behaviours in the prevention of cardiovascular disease at an early stage among the high-risk populations”.

Being reversible, the findings support the idea of better sleep for arrhythmia prevention.

“However, rest assured, we must not yet lose sleep over their findings,” cautioned Alan Kadish, MD, and Jason Jacobson, MD, in an accompanying editorial. They drew attention to a number of limitations, making the findings more theoretical than currently practicable.

Despite the study’s more sophisticated approach, “a major limitation is that arrhythmia diagnoses were obtained from diagnostic codes,” they noted. Furthermore, arrhythmias are subject to significant variability.
Arrhythmia prevention doesn’t mean cardiovascular disease prevention, they added. “[N]ot all arrhythmias have the same significance, and many are the consequence (not cause) of cardiovascular disease,” they wrote. “Alternatively, sleep disorders and arrhythmias may both simply be indicators of declining health overall and not causally linked.”

The researchers proposed potential mechanisms of action including disrupted autonomic nervous balance of sympathetic nervous and vagal outflows and metabolic changes.

The editorialists pointed out the interesting finding that genetic predisposition to atrial fibrillation significantly modified the associations. Good self-reported sleep and low genetic risk together presented a 46% lower risk of atrial fibrillation than a poor sleep pattern plus high genetic risk.

Progressively poorer sleep health scores were associated with higher incidences of atrial fibrillation and bradyarrhythmias.

Sleeping 7 to 8 hours per day, infrequent or no insomnia, and no frequent daytime sleepiness were each linked to lower arrhythmia risk.

Source: MedPage Today

Men’s Sleep Affected by Phases of the Moon

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The phases of the moon may have a far greater effect on men’s sleep than women’s, according to a new study published in Science of the Total Environment.

Prior research has produced somewhat conflicting results on the link between the lunar cycle and sleep, with some reporting an association whereas others did not. There are several possible explanations for these discrepant findings, such as that some of the results were chance findings. However, a number of past studies investigating the link between lunar cycle and human sleep did not account for confounding factors, such as obstructive sleep apnoea and insomnia.

During the waxing period, the amount of illuminated moon surface as seen from Earth increases, and the time the moon appears highest in the sky gradually shifts to late evening hours. In contrast, during the waning period, the illuminated surface decreases and the moment that time the moon is highest gradually shifts to daytime hours.

“We used one-night at-home sleep recordings from 492 women and 360 men. We found that men whose sleep was recorded during nights in the waxing period of the lunar cycle exhibited lower sleep efficiency and increased time awake after sleep onset compared to men whose sleep was measured during nights in the waning period. In contrast, the sleep of women remained largely unaffected by the lunar cycle. Our results were robust to adjustment for chronic sleep problems and obstructive sleep apnea severity,” said Christian Benedict, Associate Professor at Uppsala University’s Department of Neuroscience, and corresponding author of the study.

One mechanism through which the moon may impact sleep is sunlight reflected by the moon around times when people usually go to bed. In addition, a recent study suggests that the male brain may be more responsive to ambient light than that of females.

“Our study, of course, cannot disentangle whether the association of sleep with the lunar cycle was causal or just correlative,” concluded Prof Benedict.

Source: EurekAlert!

Impacts of Sleep Deprivation Linger a Week Later

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A Polish study found that, after a week-long recovery from sleep deprivation, only reaction speed is restored to baseline levels while other functions are still lacking.

The negative impacts of sleep deficiency are well known, and include deficits in attention and memory, increased risk of car accidents, heart problems, and other medical issues. However, while some research has addressed recovery after chronic sleep deprivation, it has been unclear how much time is needed to fully recover from prolonged periods of deficient sleep.

To shed more light on this topic, Jeremi Ochab of the Jagiellonian University in Kraków and colleagues conducted a small study, published in PLOS ONE, with several healthy adults who underwent 10 days of purposeful sleep restriction followed by seven recovery days with unrestricted sleep. Participants completed the study in their normal day-to-day environments, wearing wrist sensors to track sleep and activity. Daily electroencephalography (EEG) monitored their brain activity, and they answered daily questions (Stroop tasks) to measure reaction times and accuracy.

After 7 days of recovery, the participants had not yet returned to their baseline performance on most measures of functioning. These included several EEG measures of brain activity, rest-versus-activity patterns captured by wrist sensors, and accuracy on Stroop tasks. Only their reaction times had recovered to baseline levels.

While the researchers note that it is difficult to compare these results with other studies that employed different methods, the findings contribute new insights into recovery from chronic sleep loss. Future research could include more participants, investigate longer recovery periods, and determine in what order different functions return to normal.

The authors added: “The investigation of the recovery process following an extended period of sleep restriction reveal that the differences in behavioural, motor, and neurophysiological responses to both sleep loss and recovery.”

Source: SciTech Daily

Why REM Sleep is Important in Animals

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Researchers in Japan have discovered that capillary blood flow in the brain is increased in mice during the dream-active REM phase of sleep, possibly preventing a buildup of waste products.

Scientists have long wondered why almost all animals sleep, despite the disadvantages to survival of being unconscious. Now, researchers led by a team from the University of Tsukuba have found new evidence of brain refreshing that takes place during a specific phase of sleep: rapid eye movement (REM) sleep, where dreaming occurs.

Previous studies have seen conflicting results when measuring differences in blood flow in the brain between REM sleep, non-REM sleep, and wakefulness using various methods. For this study, the investigators used a technique to directly visualise red blood cell movement in the brain capillaries of mice during awake and asleep states.

“We used a dye to make the brain blood vessels visible under fluorescent light, using a technique known as two-photon microscopy,” explained the senior study author, Professor Yu Hayashi. “In this way, we could directly observe the red blood cells in capillaries of the neocortex in non-anaesthetised mice.”

The researchers also measured electrical activity in the brain to identify REM sleep, non-REM sleep, and wakefulness, and looked for differences in blood flow between these phases.

“We were surprised by the results,” said Professor Hayashi. “There was a massive flow of red blood cells through the brain capillaries during REM sleep, but no difference between non-REM sleep and the awake state, showing that REM sleep is a unique state”

The research team then disrupted the mice’s sleep, resulting in ‘rebound’ REM sleep, which is a stronger form of REM sleep to compensate for the earlier disruption. During rebound REM sleep, blood flow was increased even further, suggesting an association between blood flow and REM sleep strength. However, when the researchers repeated the same experiments in mice without adenosine A2a receptors (blocking these receptors makes you feel more awake after a coffee), there was less of an increase in blood flow during REM sleep, even during rebound REM sleep.

“These results suggest that adenosine A2a receptors may be responsible for at least some of the changes in blood flow in the brain during REM sleep,” said Professor Hayashi.

Given that reduced blood flow in the brain and decreased REM sleep are correlated with the development of Alzheimer’s disease, in which waste products are seen to build up in the brain, this increased blood flow in the brain capillaries during REM sleep could be important for waste removal from the brain. This study highlights the role of adenosine A2a receptors in this process, perhaps leading to the development of new treatments for Alzheimer’s disease and other conditions.

Source: University of Tsukuba

Sleep Deprivation Common in Surgeons, Impacting Performance

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New research has found that surgeons were sleep deprived prior to on-call shifts and afterwards even more so, and crucially, that sleep deprivation impacted surgical performance. 

The study is the first to focus on Irish surgeons and is published in the Journal of Surgical Research. A separate study found that short naps of 30 to 60 minutes do little to reduce sleep deprivation.

Focussing on the effects of being ‘on-call’, a frequent state for surgeons, the study explored subjective and objective metrics around sleep and performance using ‘on-call’ as a particular influencer for increased fatigue.

Surgeons frequently work 24 straight hours (or more) resulting in unavoidable sleep disturbance. This is partly due to historical associations of the Halstedian Era of Surgery to ‘reside’ in the hospital in order to properly learn, but also current staffing levels mandating surgeons to complete regular on-call work.

Participants were hooked up to electroencephalogram (EEG) machines and a validated modified Multiple Sleep Latency Test testing was used to objectively measure sleep on the morning of their on-call shift. The researchers also record other validated tests for subjective sleep and fatigue measurement. ‘Sleep latency’ refers to the time it takes to go from being fully awake to sleeping and is often an indicator of sleepiness. The surgeons in the study had early onset sleep latency before on-call, which was exacerbated further in post-call settings.

Performance was measured with standardised and validated tools. Technical performance of surgeons was assessed using the validated Simendo © surgical simulator, while cognitive performance was measured using the Psychomotor Vigilance Task (PVT) to assess objective alertness and reaction time, a known aspect of cognitive performance.

The study is the first to attempt to control for a series of confounding variables such as experience, quality and quantity of sleep, the influence of caffeine and circadian rhythm influences.

The study found that:

  • Surgeons had poor baseline sleep quality and were objectively sleep-deprived, even pre-call, when they should be in a ‘rested state’.
  • In all study participants, early onset sleep latency was seen in pre-call settings and worsened in post-call settings.
  • Early onset sleep latency was worse in trainees compared to consultants, though both groups experienced early onset sleep latency post-call.
  • As sleep-deprivation increased, diminished performance was seen in cognitive tasks and surgical tasks with greater cognitive components.
  • Higher levels of self-reported fatigue and daytime sleepiness were recorded post-call.

Technical skill performance was relatively preserved in acutely sleep deprived states but may be influenced by learning curve effects and experience in surgical tasks.

Existing models of surgical on-call were not conducive to optimising sleep for surgeons, the research found. But making changes for better sleep has challenges, such as loss of continuity of patient care, loss of trainee exposure, and reduced service delivery.

Dale Whelehan, PhD researcher in Behaviour Science at the School of Medicine and lead researcher commented: “The findings of this study tell us that current provision of on-call models preclude the opportunity for surgeons to get enough rest. Similarly, surgeons are sleep deprived before going on-call which further perpetuates the issue. The implications for performance suggest aspects of surgeons performance is diminished, particularly tasks which might be more cognitively demanding. 

“We need meaningful engagement from all stakeholders in the process, working towards the common goal of optimising performance in surgeons. This involves looking at the multifactorial causes and effects of fatigue. Part of that discussion involves consideration around how current models of on-call influence sleep levels in healthcare staff, and how it creates barriers to fatigue management in staff.”

Professor Paul Ridgway, Department of Surgery at Trinity, who supervised the study, said: “Our study is further evidence that the way we deliver emergency work alongside normal work in Ireland has to change. We need to learn from our colleagues in aviation who have mandatory rest periods before flights.”

Source: Trinity College Dublin

Dual Drug Therapy a First for Sleep Apnoea

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In a first, researchers have hit upon a combo of two existing medications to reduce the severity of sleep apnoea in people by at least 30 percent.

Millions of people around the world are affected by sleep apnoea, a condition where the upper airway from the back of the nose to the throat closes repetitively during sleep, restricting oxygen intake and causing people to wake as often as 100 times or more per hour.

Those with untreated sleep apnoea have a higher risk of developing cardiovascular disease, dementia and depression, and are two to four times more likely to crash a car than the general population. There are no approved drug therapies to treat the condition despite nearly three decades of research, and until now, the main therapy for sleep apnoea involves wearing a mask to bed, or Continuous Positive Airway Pressure Therapy (CPAP). However, many people find it uncomfortable and half the people that try it find it hard to tolerate. Second line therapies, such as mouthguards fitted by dentists, can be unpredictable and expensive.

Prior studies had shown that two classes of medication, reboxetine and butylbromide, were able to keep muscles active during sleep in people without sleep apnoea, and assist breathing ability.

Researchers used a multitude of recording instruments to measure whether reboxetine and butylbromide could successfully target the main causes of sleep apnoea.

This included balancing the electrical activity of muscles around the airway, preventing the throat from collapsing during sleep, and improving the regulation of carbon dioxide and breathing.

Results from the study, published in the Journal of Physiology, showed these medications did in fact increase the muscle activity around participants’ airways, with the drugs reducing the severity of participants’ sleep apnoea by up to one third.

Almost everyone studied had some improvement in sleep apnoea. People’s oxygen intake improved, their number of breathing stoppages was a third or more less. These new findings allow researchers to further refine these types of medications so that they have even greater benefit than what has currently been found.

Senior author Professor Danny Eckert, Director of Adelaide Institute for Sleep Health at Flinders University commented: “We were thrilled because the current treatment options for people with sleep apnoea are limited and can be a painful journey for many.

“Next, we will look at the effects of these and similar medications over the longer term. We will assess whether we can harness the benefits of one drug without needing to use them both.

“Equally, we will test whether these treatments can be combined with other existing medications to see if we can improve their efficacy even more,” he says.

Source: University of Flinders