Sleepio blog

Ask the Sleepio Expert: Is polyphasic or monophasic sleep more beneficial?

Rosie — Fri, 11 May 2012 11:00:52 +0000

Thanks to Helen for submitting this question to Prof Espie – it seems that many aspects of sleep might be considered to be polyphasic.

Got a question about sleep? Post a comment below or on the Sleepio YouTube channel and each month sleep expert Prof Colin Espie will answer a selection.

Ask the Sleepio Expert: How do frequent awakenings affect REM sleep?

Rosie — Thu, 10 May 2012 08:39:34 +0000

Thanks to Jenny for submitting this question to Prof Espie –although the stages of sleep may be disrupted by frequent awakenings, a ‘rebound effect’ on following nights may compensate for any REM sleep lost on previous nights.

Related Expert articles from the Sleepio Library:

What is REM sleep?
Is there a link between ‘dream time’ and sleep length?

Got a question about sleep? Post a comment below or on the Sleepio YouTube channel and each month sleep expert Prof Colin Espie will answer a selection.

The Sleepio Research Bulletin – May 2012

Rosie — Thu, 03 May 2012 12:20:39 +0000

Welcome all to the first ever Sleepio Research Bulletin!

We’re committed to evidence-based research into sleep. So, on a monthly basis, Sleepio will examine the latest research publications in the area of sleep, and provide you, the sleeper, with brief summaries on a selection of interesting scientific articles.

We hope you find it helpful, and we’d love to hear your views and questions. So please leave a comment below, or tweet us at @Sleepio.

Dr Simon Kyle

This month’s contents:

‘Cyberloafing’ and lost sleep
Sleep pattern disruption may increase risk of diabetes and obesity
What happens in the brain during lucid dreaming?
‘Off-label’ prescriptions commonly used to treat insomnia
Insomnia sufferers display heightened attention as they fall asleep
Could sleep apnoea be affecting your memory?

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‘Cyberloafing’ and lost sleep

We all do it: check personal emails during the working-day and visit websites not directly related to our work (e.g. the news, facebook, etc.). This so-called ‘cyberloafing’ can hinder our performance and productivity, costing employers millions each year.

In a recent article published in the Journal of Applied Psychology, David Wagner and colleagues sought to determine whether sleep was associated with cyberloafing. They performed two experimental studies, the first of which made use of data from Google Analytics, reflecting the number of internet searches for ‘entertainment-related’ topics (e.g. Youtube, Facebook, ESPN) as a proxy for cyberloafing during work hours. Taking into account previous research revealing that shifting in and out of daylight saving time (DST) can disturb our body clock and result in reduced sleep time, the researchers analysed the percentage of entertainment-related internet searches that occurred on the Monday directly after the clock-change relative to the previous and the following Monday. Analysing data from 203 metropolitan areas in the United States, for the years 2004-2009, they found that entertainment-related internet searching increased by 3.1% relative to the week before DST; and by 6.4% compared with the Monday following the week of DST. The conclusion was that DST, through effects on sleep, could lead to increased cyberloafing.

Next, the authors wished to directly test whether sleep has a role in enhancing cyberloafing, recruiting 96 undergraduate students to watch a 42 minute video-recorded lecture and provide feedback on the lecturers’ performance. Unbeknown to the participants, software was installed on the computer which could quantify how long they spent searching internet sites while they were supposed to be concentrating on the recorded lecture. The night before testing, participants wore an actigraph watch, which measures movement during the night and therefore acts as a proxy for sleep (no/little movement is interpreted as sleep). It was found that those with less sleep, as well as more interrupted sleep the night before, tended to spend more time searching websites unrelated to the task at hand (cyberloafing). Interestingly, interrupted sleep had a stronger relationship with increased cyberloafing, if an individual also scored low in conscientiousness relative to those who scored high on a scale measuring conscientiousness.

The authors conclude by recommending increased emphasis be placed on the relationship between sleep loss and productivity in the workplace:

“Global productivity losses from a spike in employee cyberloafing are potentially staggering. More generally, when employees are low on sleep, they will engage in more workplace cyberloafing. In the push for high productivity, managers and organizations may cut into the sleep of employees by requiring longer work hours. This may promote vicious cycles of lost sleep, resulting in less time spent working, which could result in more frantic pushes for extended work time. Managers may find that by avoiding infringement on employee sleep, they will get more productivity out of their employees”

The Sleepio view:

“This is a creative and well-designed study, revealing how alterations in sleep timing, continuity and length may impact productivity through increasing the tendency to engage in cyberloafing. Future work should consider experimental manipulations of sleep time in healthy populations to further characterise the role of role of sleep, as well as consideration of costs in terms of lost productivity” - Dr Simon Kyle

Original paper:

Wagner, D., Barnes, C., Lim, V., & Ferris, D. (2012). Lost sleep and cyberloafing: Evidence from the laboratory and a daylight saving time Quasi-experiment. Journal of Applied Psychology.

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Sleep pattern disruption may increase risk of diabetes and obesity

The list of consequences of a poor sleep pattern and disrupted sleep quality on our health is ever-growing and the following research does nothing to dispel these theories. The health implications of a disrupted body-clock appear to be significant but, reassuringly, may be counteracted once standard sleeping patterns are reinstated.

Several studies have suggested a possible link between poor health and alterations in ‘normal’ sleep timing and duration. Our brain and bodies have evolved to be active during the day and sedentary during night-time, and daylight helps to regulate this circadian rhythm (or body-clock). Indeed our main (master) body-clock is located in a part of the brain called the hypothalamus, which helps to synchronize other mini (or peripheral) clocks located in other parts of our body. Research suggests that altering the timing of light exposure and subsequently the timing and duration of sleep, for example in the case of night-shift workers, impacts the body-clock and may have detrimental effects on health.

Buxton and colleagues, in the journal Science Translational Medicine, recently conducted one of the longest controlled experiments into the effects of restricted sleep and altered timing of sleep. Twenty-four healthy participants recorded their sleep pattern at home for 3 weeks, spending approximately 10 hours in bed each night. They were then invited along to the specially-designed sleep laboratory at the Brigham and Women’s Hospital in Boston, where they were assigned 5.6 hours time in bed each night for three weeks. This 5.6 hour time in bed changed each night, so that sleep occurred at different times, simulating a rotating shift worker with day length modified to 28 hours (instead of the usual 24). So as not to re-set circadian rhythms, light levels were kept to a minimum in the controlled sleep lab, and there were no time-cues. After this 3 week period subjects were then ‘re-entrained’ to their normal baseline schedule.

During this restricted sleep and circadian disruption phase, the team of researchers measured glucose levels, insulin production and metabolic rate. They found that compared with baseline assessments, insulin secretion decreased by 32%, in response to a standardized meal, in parallel with dysregulated glucose regulation, with levels for some individuals being high enough to be considered ‘prediabetic’. They also measured resting metabolic rate, a measure of energy use, which was found to decrease by 8%. Over a year, it was estimated that this reduction in metabolic rate may result in increased weight gain of approximately 6 kilograms. These negative alterations to physiology, due to sleep and circadian disruption, returned to normal after participants were permitted to sleep at their normal bed and rise times.

The authors conclude that prolonged sleep restriction and circadian disruption, similar to the changes experienced by rotating shift-workers, may increase the risk of developing diabetes and obesity.

The Sleepio view:

“This work further highlights that the impact of combined sleep and circadian disruption extends beyond commonly-assessed measures of impaired cognition, to major public health issues like obesity and diabetes. The type of shift-work rotation examined in the present study would not mirror the average shift worker, but the results help demonstrate a causal role for sleep and circadian dysregulation in contributing to adverse health states” – Dr Simon Kyle

Original paper:

Buxton, O., Cain, S., O’Connor, S., Porter, J., Duffy, J., Wang, W., Czeisler, C., & Shea, S. (2012). Obesity and diabetes adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Science Translational Medicine, 4 (129).

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What happens in the brain during lucid dreaming?

We all dream, perhaps nearly every night, although we won’t always remember our dreams in the morning and, up until very recently, it would not even have been possible to measure the brain activity associated with these dreams and their content. However, new research using ‘lucid dreamers’ and brain imaging recordings, has made this possible for this first time, with some interesting results.

We tend to have our most vivid dreams during REM sleep and are more likely to remember these dreams if we wake up during or close to this phase of sleep. Research into brain activity has revealed the brain to be as ‘metabolically active’ during REM sleep as it is during wakefulness. When considering regional changes in the brain, studies have revealed that specific brain areas related to arousal (brainstem, thalamus), emotion (e.g. amygdaloid complexes, anterior cingulate), and perception (extrastriate temporo-occipital cortices) demonstrate increased activity; perhaps reflecting the emotional intensity and perceptual (auditory/visual) aspects characteristic of dreams. On the other hand, brain imaging studies have demonstrated reduced activation in areas involved in attentional and executive abilities (dorsolateral prefrontal, orbitofrontal cortices, precuneus), which may account for our inability to be self-aware during a dream or exert control over dreamed events.

There are however, some people with the rare ability to be aware that they are in a dreamed state and can subsequently influence actions that occur during their dreams. This is known as ‘lucid dreaming’ and may comprise features of both wakefulness and sleep with the individual being categorically asleep (in REM sleep) according to objective polysomnographic sleep recordings, but able to access memory and control the content/events of the dream. Indeed a recent study indicated that, when entering a dream during brain imaging recordings (fMRI, EEG), lucid dreamers can communicate to experimenters by a) initiating a pre-determined pattern of eye-movements; and b) ‘clenching’ their right and left hand in a pre-defined manner (Dresler et al., 2011, Current Biology). As muscle tone is lost during REM sleep, this ‘clenching’ only occurs within the dream. However, the experimenters were able to record the brain response of the dreamed clenching, by activation demonstrated in the sensorimotor cortex corresponding to either the left or right hand. This was the first demonstration that we might be able to observe the nature of specific dreamed actions through brain imaging recordings.

In a follow-up report, currently in press for publication in the journal SLEEP, Dresler and colleagues extended this work by analysing brain activity during periods of lucid dreaming and contrasting it with brain activity that occurred during non-lucid dreaming. Four healthy participants, who reported the ability to lucid dream were evaluated using combined functional magnetic resonance imaging (fMRI) and electroencephalography (EEG), allowing the researchers to look at their brain activity. Lucid dreams were confirmed when the subject carried out pre-determined left-right-left-right eye-movements and through dream reports on awakening. Only one subject successfully met the criteria for lucid-dreaming (rendering this a single case report). Brain activity observed during this defined phase of lucid-dreaming REM sleep was then compared with adjacent non-lucid REM sleep. The main findings were that, in contrast to non-lucid REM sleep, lucid REM sleep was associated with increased activity in brain regions associated with several reflective cognitive abilities, permitting the dreamer to become self-aware during their dream state, access memory, and experience agency.

In light of the findings, the authors also allude to the potential use of lucid dreaming to successfully treat nightmare disorders, in which emotional brain responses have been hypothesized to be exaggerated during REM sleep. Harnessing of lucidity during dreaming may help exert control over the experience of intense nightmares however, further work is required to test these hypotheses.

The Sleepio view:

“Although essentially a case report study, this work helps to define for the first time the brain correlates of lucid dreaming, and how this state differs from non-lucid REM sleep. ” Dr Simon Kyle

Original paper:

Dresler, M., Wehrle, R., Spoormaker, V., Koch, S., Holsboer, F., Steiger, A., Obrig, H., Sämann, P., & Czisch, M. (2012). Neural correlates of dream lucidity obtained from contrasting lucid versus non-lucid REM sleep: a combined EEG/fMRI case study. SLEEP.

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‘Off-label’ prescriptions commonly used to treat insomnia

It is common knowledge amongst medical practitioners and clinical researchers that a wide range of medications are prescribed ‘off-label’, meaning that the drug in question has not been approved by a regulatory body to treat a particular condition. The extent to which this occurs has been hard to determine due to measurement limitations but, as off-label prescribing in certain illnesses has been shown to be related to the occurrence of adverse events and side-effects, it remains an important area of research.

When prescribing, it is often the case that the illness does not have to be coded (registered) in order to link it with the medication prescribed. In a recent article by Dr Eugale and colleagues, published in the Archives of Internal Medicine, the authors took advantage of a relatively new electronic health record system which asks physicians to record what drug they have prescribed and for what illness. They were then able to quantify the level of ‘off-label prescribing’ for various conditions and the factors that are associated with it.

The study took place in Quebec, Canada, over 5 years and included 113 physicians, giving out over 250,000 unique prescriptions. Off-label prescriptions accounted for 11% of all prescriptions and, according to standard criteria, nearly 80% of these off-label prescriptions were given out without strong scientific evidence for a certain condition. Drugs that target the central nervous system (e.g. anti-depressants, analgesics, anti-epileptic medication) were found to be the most commonly-prescribed medication off-label (26% of all off-label prescriptions) and that physicians who tended to endorse greater levels of evidence-based practice were less likely to prescribe ‘off-label’. It was also found that patients with co-morbidities (greater number of health problems) were less likely to be prescribed medications off-label, and that drugs approved for use in several conditions (3 or 4) tended to be less likely to be prescribed ‘off-label’ for other conditions relative to drugs that were approved for just one or two conditions.

Insomnia was one of the top ten conditions commonly given off-label prescriptions with approximately 44% of over 10,000 prescriptions for insomnia being considered off-label. The three most common off-label prescriptions for insomnia were oxazepam, trazodone and clonazepam.

The authors note that the introduction of electronic recording systems helps identify illnesses where off-label prescribing is common, paving the way for rigorous controlled research to be conducted on these medications that physicians like to use, but that are currently not indicated.

The Sleepio view:

“Off-label prescribing is particularly common for insomnia. Physicians clearly feel, based on clinical practice and experience, that certain (off-label) medications can be effective or might have less side-effect potential. The recording system, investigated in the above study, helps identify what these medications are and encourages enhanced research focus on determining their safety and effectiveness. The results also suggest a need for physician education around evidence-based medicine” – Dr Simon Kyle

Original paper:

Eguale, T., Buckeridge, D., Winslade, N., Benedetti, A., Hanley, J., & Tamblyn, R. (2012). Drug, patient, and physician characteristics associated with off-label prescribing in primary care. Archives of Internal Medicine. doi:10.1001/archinternmed.2012.340

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Insomnia sufferers display heightened attention as they fall asleep

It’s likely that you will have experienced a time when you weren’t sure if you were awake or asleep but had no objective way of knowing for certain. This discrepancy between objective and subjective sleep is a relatively common finding in individuals with insomnia and a number of studies have shown that some people with insomnia tend to think they have slept less than they have (according to objective measurement with Polysomnography).

This phenomenon has shown to be the case for the period taken to fall asleep, with patients experiencing wakefulness despite objective recordings categorically demonstrating sleep. Individuals with chronic insomnia, often find their attempts to initiate sleep to be interfered by racing, intrusive thoughts, and attention to random environmental noise. This can lead to increased focus on, and active attempts to initiate, sleep; making it even harder to fall asleep!

In a study published this month in the journal SLEEP, Dr Corsi-Cabrera and colleagues investigate what happens in the brains of 10 patients with primary insomnia (poor sleep in the context of no additional medical, psychiatric or sleep disorder) as they transition between sleep and wake. The team from Mexico and Cuba conducted a fine-grained analysis of the electrical brain activity which occurred as insomnia patients fell asleep relative to good sleeping subjects. Specifically, they looked at the power of certain brain frequencies (known to be associated with arousal and attention) and how different brain regions interact with one another. Using a greater number of electrodes and analysing shorter durations of time (epochs) allowed the investigators to address the localised brain changes which occurred during this wake to sleep transition.

The authors found that insomnia patients, compared with normal sleepers, showed evidence of greater beta EEG activity just prior to sleep and during stage 1 of sleep. This activity has previously been associated with enhanced attention and sensory information processing, suggesting that patients with insomnia are hyperaroused or hypervigilant when initiating sleep. It was also found that patients had enhanced activity within a set of related brain regions subserving attention, during the wake to sleep transition, suggesting poor sleepers may have difficulty disengaging from their environment and internal thoughts.

The authors conclude from their exploratory study that “frontal deactivation and the disengagement of the brain regions involved in executive control and willed action, inner attention, planning future actions, retrieval of past experience, and self-awareness are impaired”, for patients with primary insomnia.

The Sleepio view:

“This exploratory work is very promising. Further study is required around how these functional brain alterations relate to objective versus subjective sleep discrepancies, as well whether successful treatment may modify or normalise this activity” – Dr Simon Kyle

Original paper:

Corsi-Cabrera, M., Figueredo-Rodríguez, P., del Río-Portilla, Y., Sánchez-Romero, J., Galán, L., & Bosch-Bayard, J. (2012). Enhanced frontoparietal synchronized activation during the wake-sleep transition in patients with primary insomnia. SLEEP, 35 (4).

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Could sleep apnoea be affecting your memory?

Over the past decade several studies have identified that normal, healthy sleep plays an important role in the reorganisation and consolidation of newly-formed memories. More recently this has opened up the question of whether the poorer quality sleep found in those with sleep disorders could have an impact on these processes.

Previous research into this subject has shown performance on tasks that involve the learning of motor skills (e.g. typing a sequence of letters on a keypad as quickly and as error-free as possible) to improve between two points in time (e.g. 10pm to 10am, or 10am to 10pm). This improvement tends to be much larger however, where people have slept rather than remained awake between these testing sessions. It therefore appears that the unique physiology of sleep states are likely to be important in the consolidation of procedural motor memories such as these.

In a recent study published in PLoS One, Dr Ina Djonlagic and colleagues, from the Division of Sleep Medicine at Harvard Medical School, sought to investigate whether fragmented, disturbed sleep might actually result in the impairment of this normal overnight enhancement of memory. To do this they compared 16 healthy control subjects with 15 patients with mild obstructive sleep apnoea (OSA), a sleep disorder which can result in several micro-arousals (very brief awakenings) during sleep, as well as intermittent hypoxia (reductions in oxygen supply) due to reductions in airflow.

The two groups slept at the sleep lab, completing a motor sequence task (MST) between 8 and 9pm, prior to sleep, and between 6.30 and 7.30 am the next morning post-sleep. The MST involved participants learning a number sequence (e.g. 2-4-1-3-2) by typing the digits on a keypad without looking at the keypad throughout the task. Their performance was assessed by comparing the number of times they correctly typed the sequence in a 30 second interval, both before and after the period of sleep.

The main finding was that healthy control subjects showed an average improvement of 15%, pre-to-post sleep, in the number of correctly typed number sequences. OSA patients, on the other hand, showed an average improvement of just 1%, being significantly more impaired than healthy subjects. Interestingly, the number of micro-arousals during sleep was the factor most strongly related to impaired overnight memory consolidation but both the stages of sleep and total time asleep did not differ between the two groups. Further tests used to probe attention and sleepiness, revealed no difference between the two groups, ruling out the possibility that memory performance differences were due to the effects of increased sleepiness and/or impaired attentional capacity.

In conclusion, the authors note:

“Concurrent with recent animal research, we suggest that increased arousals from sleep constitute an important predictor of sleep dependent memory processes presumably interrupting the transfer of labile memories from the hippocampus to the neocortex for long-term storage”.

The Sleepio view:

“This work highlights that increased micro-arousals, in the absence of gross impairment or alterations to sleep composition and duration, can have negative effects on the sleeping brain’s ability to consolidate motor memories. Further investigation with additional sleep-disordered patient populations is warranted” – Dr Simon Kyle

Original paper:

Djonlagic, I., Saboisky, J., Carusona, A., Stickgold, R., & Malhotra, A. (2012). Increased sleep fragmentation leads to impaired off-line consolidation of motor memories in humans. PLoS One, 7 (3).

Sleep patterns – what keeps us in sync?

Rosie — Fri, 27 Apr 2012 11:22:31 +0000

Dr Simon Kyle explains the processes that govern our daily sleep pattern.

Sleep is an automatic process meaning that it is out of our own direct or voluntary control. However, whether we are awake or asleep we are at the mercy of two biological processes: sleep homeostasis, commonly known as (1) ‘sleep pressure’; and (2) the circadian rhythm, otherwise known as the ‘body clock’. These two processes work in harmony to promote a healthy sleep pattern and good, consolidated sleep at night.

Sleep pressure
Sleep pressure can be thought of as the brain’s need for sleep, growing with increasing amounts of time spent awake and alert. In this way, the pressure to sleep is directly related to the amount of time that we have been awake. For example, when we wake-up in the morning after a good night’s sleep, we will have a very low sleep pressure or ‘need to sleep’. As we continue throughout the day, sleep pressure will begin to accumulate (a bit like an hourglass egg-timer) and, by bedtime, we will have a great amount of pressure to sleep. By going to bed and having another good night’s sleep, our sleep pressure will be reset for the start of the next day.

The body clock
The circadian rhythm is an internally generated biological rhythm that allows a number of processes to rise and fall over the twenty four hour period. Commonly, its effects are mostly realised with jet lag when one travels through many different time zones rapidly. This is when the circadian rhythm is out of synchrony with the new environment and can take a number of days to go back to normal. Similar, ‘out-of-sync’, patterns may be observed in circadian rhythm sleep disorders such as ‘delayed sleep phase disorder’, whereby individuals experience a chronic pattern of sleep disturbance due to changes or misalignment in the circadian timing of their sleep.

In a good sleeper, who is ‘in-sync’’ with the environment, the circadian rhythm will naturally rise in the early morning, promoting wakefulness and alertness – this is sometimes known as the alerting force. As the day continues, the circadian rhythm will promote wakefulness until it reaches a peak at about midday. After this time, the circadian rhythm will start to dip. This initial fall is known as the ‘post lunch dip’ (you may be familiar with greater feelings of sleepiness after lunch) and as a time for a siesta in other cultures. As we continue through the day levels of the hormone ‘melatonin’ rise and the circadian rhythm continues to fall, promoting less arousal than before. With the onset of bedtime and sleep, the circadian rhythm drops to the lowest level and helps to maintain sleep. In this way, sleep pressure is very high, while the alerting effect of our body clock is low, creating the optimal opportunity to sleep.

Read more about sleep and sleep disorders from Dr Simon Kyle in the Sleepio Expert Library.

Ask the Sleepio Expert: Why do I swing between good and bad nights?

Rosie — Thu, 26 Apr 2012 09:20:55 +0000

Thanks to Lesley for submitting this question to Prof Espie – It seems that the ‘pendulum effect’ of good and back nights is quite common but can be effectively addressed by a combination of cognitive behavioural techniques to improve poor sleep.