Tag: sleep

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

Rough Night? Perhaps Skip the Coffee, Study Suggests

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Depending on coffee to get through the day after a night of poor sleep isn’t always the answer, suggests a new study from Michigan State University.

Researchers from MSU’s Sleep and Learning Lab, led by psychology associate professor Kimberly Fenn, assessed the effectiveness of caffeine in counteracting the negative effects of sleep deprivation on cognition. It turned out that caffeine only helps up to a point.

The study assessed the impact of caffeine following a night of sleep deprivation. The study recruited over 275 participants who were asked to complete a simple attention task as well as a more challenging ‘placekeeping’ task where tasks had to be completed in a specific order without skipping or repeating steps.

Asst Prof Fenn’s study is the first to investigate the effect of caffeine on placekeeping after a period of sleep deprivation.

“We found that sleep deprivation impaired performance on both types of tasks and that having caffeine helped people successfully achieve the easier task,”  said Asst Prof Fenn. “However, it had little effect on performance on the placekeeping task for most participants.”

She added: “Caffeine may improve the ability to stay awake and attend to a task, but it doesn’t do much to prevent the sort of procedural errors that can cause things like medical mistakes and car accidents.”

The US population has a pervasive lack of sleep, a problem that has intensified during the pandemic, Asst Prof Fenn said. Having inadequated sleep impacts not only cognition and mood, but can eventually weaken immunity.

“Caffeine increases energy, reduces sleepiness and can even improve mood, but it absolutely does not replace a full night of sleep, Fenn said. “Although people may feel as if they can combat sleep deprivation with caffeine, their performance on higher-level tasks will likely still be impaired. This is one of the reasons why sleep deprivation can be so dangerous.”

Asst Prof Fenn said that the study has theoretical and practical implications.

“If we had found that caffeine significantly reduced procedural errors under conditions of sleep deprivation, this would have broad implications for individuals who must perform high stakes procedures with insufficient sleep, like surgeons, pilots and police officers,” she concluded. “Instead, our findings underscore the importance of prioritising sleep.”

The study can be found online.

Source: Michigan State University

Study Explores the Circadian Rhythm Control Centre

Woman sleeping with an alarm clock on bedside. Photo by cottonbro from Pexels

Researchers in Japan have offered new insights into how the brain’s circadian rhythm control centre regulates behaviour.

Circadian rhythms are a force in the background that shapes many human behaviours such feeling tired and falling asleep, as well as influencing our health. Michihiro Mieda and his team at Kanazawa University in Japan are researching just how the brain’s circadian rhythm control centre regulates behaviour.

The control centre, known as the superchiasmatic nucleus, or SCN, contains many types of neurons that transmit signals using the molecule GABA, but little is known about how each type contributes to our bodily rhythms. In this most recent study, the researchers focused on GABA neurons that produce arginine vasopressin, a hormone that regulates kidney function and blood pressure in the body, and which the team recently showed is also involved in the regulation of the interval of rhythms produced by the SCN.

To examine the function of these neurons separate to all others, the researchers first deleted a gene in mice which was needed for GABA signaling between neurons, but only in vasopressin-producing SCN neurons. “We removed a gene that codes for a protein that allows GABA to be packaged before it is sent to other neurons,” explained Mieda. “Without packaging, none of the vasopressin neurons could send out any GABA signals.”

Thus, these neurons could not use GABA to communicate with the rest of the SCN anymore. The mice showed longer periods of activity, beginning activity earlier and ending activity later than control mice, a simple enough result. It might seem that losing the packaging gene in the neurons disrupted the molecular clock signal but the result was not so simple. Closer examination deepened the mystery as the molecular clock seemed to progress unhindered.
Using calcium imaging, the researchers examined the clock rhythms within the vasopressin neurons. They found that while the rhythm of activity matched the timing of behaviour in control mice, this relationship was disturbed in the mice with missing GABA transmission in the vasopressin neurons. The rhythm of SCN output, ie SCN neuronal electrical activity, in the modified mice had the same irregular rhythm as their behaviour.

“Our study shows that GABA signaling from vasopressin neurons in the suprachiasmatic nucleus help fix behavioral timing within the constraints of the molecular clock,” concluded Mieda.

Source: News-Medical.Net

Journal reference: Maejima, T., et al. (2021) GABA from vasopressin neurons regulates the time at which suprachiasmatic nucleus molecular clocks enable circadian behavior. PNAS. doi.org/10.1073/pnas.2010168118.

Sleep Doctors are Concerned Over CPAP Negative Evaluation

Sleep doctors are concerned about a draft report casting doubt on the clinical benefits of continuous positive airway pressure (CPAP), the clinical gold standard for sleep apnoea.

Reviewers from the Agency for Healthcare Research and Quality (AHRQ) found that studies of continuous positive airway pressure (CPAP) have consistently failed to show improvements in non-sleep-related outcomes linked to obstructive sleep apnea (OSA), such as stroke, heart attack, diabetes, and depression.

The report concluded that the published evidence “mostly does not support that CPAP prescription affects long-term, clinically important outcomes,” and it highlighted research gaps and methodological weaknesses in the available studies, along with significant CPAP compliance issues, which have all contributed to the failure to show long-term benefits for the treatment.

OSA specialists who spoke to MedPage Today about AHRQ’s research review agreed that CPAP remains by far the most effective treatment for sleep-related symptoms of OSA. They worried that the report could be misinterpreted as meaning that the treatment has no value. 
The US offers coverage for CPAP therapy under Medicare for patients with OSA, amounting to hundreds of millions of dollars per annum.. One recent study of Medicare recipients 56% were at high risk for OSA and possible candidates for treatment.

“The big fear that I have, and many of my colleagues have, is that the way this report is worded could easily be misinterpreted as saying that prescribing CPAP doesn’t improve these (long-term) outcomes, so we shouldn’t be paying for it,” said David Rapoport, MD, who directs the sleep medicine research program at the Icahn School of Medicine at Mount Sinai in New York City.

He said that it is widely recognised that CPAP is the most effective treatment for improving OSA symptoms, such as snoring and daytime sleepiness.

“Nothing else even comes close,” he said. “CPAP is really a remarkable treatment for addressing the breathing disorder associated with obstructive sleep apnea. But it has to be used, and compliance remains a big issue.”

The AHRQ review included data from 47 long term (≥6 or 12 months) randomised clinical trials for OSA.

Investigators noted that the studies used “highly inconsistent” definitions of measures such as respiratory events, as well as the Apnoea-Hypopnoea Index (AHI) metric.

“No standard definition of this measure exists and whether AHI (and associated measures) are valid surrogate measures of clinical outcomes is unknown,” the report states.

Elise Berliner, PhD, of AHRQ, told MedPage Today that addressing the inconsistencies and limitations of the existing studies should be a top priority of the sleep research community. She added that definitions should be standardised.

“I do think the community needs to get together and figure out how to do better studies,” she said. “We need larger and longer studies, and there is also the issue of compliance. In most of the studies, people were not using these devices all night long.”

The report found that the existing randomized controlled trials provide low strength of evidence that CPAP affects all-cause mortality, stroke and myocardial infarction risk, or other cardiovascular outcomes. Researchers also concluded that insufficient evidence exists showing an impact for CPAP on the risk for automobile accidents, depression, and anxiety and hypertension.

Sanjay Patel, MD, of the University of Pittsburgh, agreed inconsistency and poor CPAP compliance in sleep studies have made it difficult to assess its  impact on mortality and most other long-term outcomes.

But he, like Dr Rapoport, expressed concern that some will interpret the findings to mean that CPAP is ineffective.

“The thinking in the field has been that treatment may help prevent diseases like diabetes and heart disease that are related to sleep apnea,” he told MedPage Today. “This report says we don’t have good evidence on this, but it doesn’t really distinguish between outcomes where we do and do not have enough research to say definitively that treatment with CPAP isn’t beneficial.”

Dr Patel served on the writing committee for the American Academy of Sleep Medicine’s (AASM) latest clinical practice guidelines for OSA treatment with CPAP. He observed that the guidelines differ from the AHRQ findings, in that CPAP has been shown to lower blood pressure in hypertensive OSA patients.

The AHRQ analysis was also restricted to 6 month follow-ups or longer, while the AASM’s writing committee considered studies with shorter follow-up times.

“The effect [of CPAP] on blood pressure can be seen at 1 month,” he said. “Multiple studies with 3 months of follow-up show improvements in blood pressure, but AHRQ did not look at those studies.”

While CPAP is still considered the most effective treatment for OSA, Dr Rapoport said there is a growing recognition within the sleep medicine field that it’s not for everyone, given the ongoing issues with compliance.

“In the past, other treatments such as mandibular advancement devices have been marginalized,” he said. “These treatments don’t work nearly as well as CPAP in terms of lowering AHI, but they do work well for many patients, and people who are prescribed them actually use them. Until recently, there wasn’t much acceptance that this was good enough. But there is now greater recognition that we should maybe be prescribing treatments that aren’t perfect if people are more likely to use them.”

Source: MedPage Today

Sleep Apnoea Treatment May Reduce Risk of Dementia

Older adults receiving positive airway pressure therapy for obstructive sleep apnoea (OSA) may have a lower risk of developing Alzheimer’s disease and other kinds of dementia, according to a new study.

In a nationally representative study, Researchers from Michigan Medicine’s Sleep Disorders Centers analysed Medicare claims of over 50 000 Medicare beneficiaries 65 and older with OSA. They sought to find out whether people using positive airway pressure therapy had less risk of receiving a new diagnosis of dementia or mild cognitive impairment over the next 3 years, compared to those not using positive airway pressure therapy.

“We found a significant association between positive airway pressure use and lower risk of Alzheimer’s and other types of dementia over three years, suggesting that positive airway pressure may be protective against dementia risk in people with OSA,” said lead author Galit Levi Dunietz, PhD, MPH, an assistant professor of neurology and sleep epidemiologist.

The findings stress the impact of sleep on cognitive function. “If a causal pathway exists between OSA treatment and dementia risk, as our findings suggest, diagnosis and effective treatment of OSA could play a key role in the cognitive health of older adults,” said principal investigator Tiffany J. Braley, MD, MS, associate professor of neurology.

Obstructive sleep apnoea is a condition where there are episodes of complete or partial collapse of the airway with an associated decrease in oxygen saturation or arousal from sleep. This disturbance results in fragmented, nonrestorative sleep, and is associated with a variety of other neurological and cardiovascular conditions. Many older adults are at high risk for OSA. Dementia is prevalent as well, with roughly 5.8 million Americans currently living with it, said Prof Braley.

Source: Medical Xpress

Journal information: G L Dunietz et al, Obstructive Sleep Apnea Treatment and Dementia Risk in Older Adults, Sleep (2021). DOI: 10.1093/sleep/zsab076