Monthly Archives: January 2016

Upcoming Articles

While trying to decide what article I’d like to write next I realised that I haven’t really introduced people to the basics of sleep science and why people like me get money to research it. I’ve already used terms which are familiar to most people, but there’s also been some which are probably less so. Hopefully, I’ve explained what these terms are in sufficient detail so far, yet I still think it makes sense to take a step back and examine why we sleep, how we measure it, and why its worth researching in the first place.

I will initially post these articles in a small, bit-sized, format so that they remain informative but also interesting. I’ll likely expand on these in the future, but their size should serve the purpose for the time being.

Thank you to everyone who has read and enjoyed these articles so far btw. These articles have really helped with my own research, and I hope they continue to interest you all!

Inquisitive Tortoise


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The Creature at the End of the Bed: What is Sleep Paralysis?

Sleep Paralysis

A fitting depiction of the sleep paralysis experience for many.

My limbs won’t move. I can’t scan the room or, more importantly, run if I needed to. This feeling in itself is terrifying, but I become aware of an evil presence in the room. It’s behind me and is waiting there. All I’m aware of is a jagged shadow which means me some ill. I’m desperate to move, to escape, to scream out and run from this figure watching me. Minutes pass and my focus is on moving, willing my failing limbs to spring into action. Suddenly they return back to life and I instinctively look towards the corner of the room where I felt a malevolent being was sizing me up. There’s nothing there but darkness and my old blue wooden wardrobe. Shaken and tired, I attempt to drift back to sleep and forget that the shadow could still be out there.

My first, and only, experience with sleep paralysis occurred when I was about 6 years old and coincided with my sleep-walking phase. It was a brief but terrifying experience and although I don’t remember it perfectly, the feeling of vulnerability and that shadow’s presence remain with me.  The experience of sleep paralysis differs from person to person but there are constants to everyone’s experience. There is the characteristic paralysis of voluntary muscles and often, but not always, this is accompanied by hallucinations which can leave the person frightened and disoriented. The hallucinations experienced by sufferers of sleep paralysis also appear deeply embedded in different cultures, literature and history (see sleep paralysis as a cultural phenomenon below).

These hallucinations can be grouped into intruder, incubus and vestibular hallucinations. The intruder hallucination, whereby there is a feeling that there is a being in the room with you, with the feeling of malevolent intent is the type I experienced as a young child. However, experiences of a great weight on your chest attributed to a demon-like creature and the feeling of floating can be identified as incubus and vestibular hallucinations respectively. These experiences are particularly distressing for those who are unfamiliar with their cause and has led some to wrongly believe they were suffering from psychosis.

Although a bizarre experience, it is not all that uncommon. A large systematic review (a comprehensive report which gathers all of the studies, in theory, ever conducted on a topic) of the prevalence of sleep paralysis found that “7.6% of the general population, 28.3% of the student population, and 31.9% of psychiatric patients experienced at least one episode of sleep paralysis” (Sharpless & Barber, 2011). It’s interesting to note that it should be so prevalent amongst student populations.

So, what is at the root of sleep paralysis episodes? It appears that sleep paralysis is linked to REM sleep and the transition to and from this stage of the sleep cycle. Interestingly, in a sleep disorder known as narcolepsy, characterised by sudden onsets of sleep, the prevalence of sleep paralysis is around 50%. This is considerably higher than the normal population, and it might be due to the sudden onset of REM sleep seen in individuals with narcolepsy. Moreover, narcolepsy is also associated with partial sleep paralysis. This is where there is some limited movement available to the individual but they are likely paralysed and experience the powerful and frightening hallucinations seen in sleep paralysis.

In my last article, I talked about how it is possible to induce sleepwalking in those with a genetic risk by sleep depriving them. It appears that the same trick can be useful in eliciting sleep paralysis episodes in students. A study by Takeuchi and colleagues (1992) showed that by waking students up at just the right time they were able to elicit sleep paralysis in their sample. More specifically, by waking up participants when they were just about to enter REM, they were able to manipulate it so that participants were more likely to go directly into REM sleep as they drifted off again. However, this technique is far from perfect in eliciting sleep paralysis as out of 64 successful REM interruptions, only 6 episodes of sleep paralysis were recorded in 5 out of 16 participants. This suggests that sleep onset REM is involved in sleep paralysis but there are likely other factors which play a role here. For example, stress and physical tiredness (beyond being woken up in a sleep laboratory) may also contribute to the likeliness of sleep paralysis occurring. This may explain why student and psychiatric populations are more prone to sleep paralysis episodes.

As I have already, hopefully, addressed with sleepwalking, there is a clear and long history of sleep paralysis as recorded in literature and historical medical reports. We have identified the different subtypes, linked it to a particular stage of sleep and started to identify some connections with other sleep disorders (e.g. narcolepsy). However, this is largely where our understanding of the phenomenon ends. It appears that problems in the REM stage of sleep are important in the production of sleep paralysis but more work is needed to understand what these are and why they are important.

Sleep Paralysis as a Cultural Phenomenon

S5765870281_a51d288e54_zleep paralysis occurs across a wide range of different cultures and there is historical evidence of it occurring throughout the history of medicine and literature. Folk terms such as the “old hag”, the “Pandafeche”, and visitations by demonic presences such as succubi and incubi have been attributed to sleep paralysis.
Many of these lay blame for experiences on paranormal or spiritual beings, with a focus on witch or ghost-like beings (old hag and pandafeche), and given the content of hallucinations experienced alongside sleep paralysis this is not surprising.

The painting, ‘The Nightmare’ by Henry Fuseli is commonly believed to be a depiction of sleep paralysis and a case study from the 1600s exists which describes sleep paralysis in vivid detail (Kompanje, 2008). Interestingly, the previous case study also highlighted how body position while sleeping might contribute to sleep paralysis and hallucinations experienced with it. There is some recent evidence which suggests that lying in a supine position (on your back, face up) may be associated with increased rates of sleep paralysis and associated hallucinations. The 17th century case study provided the earliest evidence of this facet of sleep paralysis.

Inquisitive Tortoise

Image Credits:

Header Image: Sleep-paralysis-pic 

Additional Info Image: Demon

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What Causes Sleepwalking?

Sleepwalking Image.jpg


“Jack… Jack? Jack…!” A flash of lights and the whizz of cars speeding past suddenly assault my senses. In the background, I’m dimly aware of my name being called. In a few more seconds I have woken more fully and, as if suddenly coming up from underwater, I hear the shouts and then realise why my name being called out in increasingly frantic tones. “Close the door! Jack…! Close it!”

The car door was halfway open and I had just taken off my seat-belt. I was, as I began to realise, a mere second or two from stepping out of the family car hurtling along the M6. Suffice to say, I wasn’t trusted with the privilege of a child-lock-free place in the car after that.

Sleepwalking can be considered to be one of a number of different but related disorders which come under the global title of ‘disorders of arousal’. Confusional arousal, sleep-related eating disorder and sleep-related abnormal sexual behaviours are all considered to be forms of, or to be related to, sleepwalking. These are behaviours of differing complexity, all of which are performed while an individual is asleep and of which they typically have little to no memory afterwards. Sleepwalking is typically classified by seemingly automated behaviours which may appear to serve some purpose.

It is not uncommon in childhood and, unlike my own experience, may cause a little distress and embarrassment but hardly have the potential for injury or death. In fact, sleepwalking during childhood occurs in as many as 17% of children at its peak age of 11 years old, and it is generally accepted that we grow out of this behaviour. Indeed, only around 1-4% of the adult population report sleepwalking episodes. Given that the brain and our sleep and bodily rhythms go through major changes during adolescence, this shift from a common phenomenon to relative rarity is far from surprising. Incidentally, as we will later see, the changes in the structure of sleep from childhood to adulthood may explain why we may remember the odd embarrassing sleepwalking episode as a child but not as an adult.

However, it is considered less than benign if sleepwalking becomes common in our adult lives. In both childhood and adult sleepwalkers, there is a relationship between sleepwalking and anxiety, psychosis and other parasomnias, such as night terrors. The main concern in adulthood is the risk of physical harm to the sleepwalker or others. All of us have probably been exposed to what sleepwalking is and what forms it can take. This can range from simply walking around the house to preparing food, having a conversation or even, in rare instances, driving. Given the range of complex behaviours which can occur during a period of sleepwalking, it should come as no surprise that some consider its occurrence in adults far from benign. Instances of murder, sexual assault and personal injury are purported to have taken place during a sleepwalking episode.

It should be stressed that this is far from the norm among adult sleepwalkers. These concerns are rare and although the sleepwalker may harm themselves or their bed-partner, it is typically the loss of sleep and subsequent daytime sleepiness which are of primary concern to doctors.


What Causes Sleepwalking?


So, what actually causes sleepwalking and why do some people seem to be prone to it whereas others don’t? First we need to have an idea of what happens as we fall asleep and what our brain is doing as we drift off.

The brain does not go to sleep in a unitary manner. Although we may feel ourselves start to drift into sleep as we steadily lose consciousness, the brain enters a sleep state in a progressive, region-specific manner. That is, brain regions which have been active over the course of the day or prior to sleep take longer to enter a sleep-like rhythm. As a result of this facet of sleep physiology, it is possible to observe certain regions of the brain as awake while others are technically asleep. Among those prone to sleepwalking, it is observed that motor regions of the brain may exhibit ‘wakefulness’ while areas responsible for higher cortical functions such as the prefrontal cortex are ‘asleep’. This may explain why someone can seemingly carry out complex actions but yet still be asleep, but it does not tell us how this occurs in the first place. Why is it that this pattern of localised wakefulness only results in sleepwalking in a small subset of adults and a larger subset of children? It seems the pattern of sleep in sleepwalkers sheds some light on this question.

During a typical night’s sleep, we progress through cycles which see us move from light sleep to deep sleep and back again about 4-5 times. Each of these cycles lasts about 90-110 minutes and marks our shift from non-rapid eye-movement (NREM) sleep to rapid eye-movement (REM) sleep. NREM sleep consists of 4 separable stages and dominates the first half of the night, whereas REM sleep is where we typically dream and dominates the latter half of the night. These stages can be tracked using a technique called polysomnography, whereby electrodes are placed on an individual’s head and the underlying neural activity is recorded while they sleep.

Researchers are interested in the function of these different stages of sleep (NREM is made up of four distinct stages) and how they might serve memory consolidation, daytime functioning and even mental health. How does sleepwalking fit into all of this then? Well, research seems to point to the deepest stage of NREM sleep, known as slow wave sleep (SWS), as a potential culprit.

When you compare individuals with a history of sleepwalking against those without in the sleep laboratory, you find some interesting differences. Namely, those with the history of sleepwalking episodes tend to show a fragmentation of their slow-wave sleep compared to the controls. It seems that sleepwalkers are more prone to waking up, albeit very briefly, during SWS sleep, and it is this occurrence which may precede a sleepwalking episode. Moreover, sleep deprivation over 24 hours and experimentally induced awakenings during NREM sleep can induce sleepwalking. However, there’s an important caveat to this: these findings are only found in those already prone to sleepwalking episodes (i.e. a recorded history of adult sleepwalking). Individuals who did not report sleepwalking did not start sleepwalking purely because they were deprived of sleep, or woken up at just the right time.

Problems during SWS fits with our earlier identification of sleepwalking as being commonly found in childhood. The percentage of the sleep cycle taken up by SWS is increased in childhood and decreases as we grow older. As we have already identified, sleepwalking can occur during any stage of NREM sleep but it is during SWS that it is most commonly ‘found’. The next question we’re presented with then is what might lead an individual to be prone to these ‘micro-arousals’ during SWS? The short answer is that we’re still not quite sure. The evidence available suggests that genetic factors play an important role in leading someone to be prone to sleepwalking episodes. For example, you are more likely to have a disorder of arousal such as sleepwalking if another relative also suffers from it.

Other factors beyond genetics have been identified as being linked to sleepwalking. A review last year identified sleep deprivation (which we have covered), stress, forced arousal during sleep (such as needing to go the toilet or a loud noise nearby), an unfamiliar sleep environment and medications (such as those used to treat schizophrenia) as potential triggers for an episode of sleepwalking and other arousal disorders. Interestingly, what all of these factors seem to have in common is that they influence SWS –by either deepening or fragmenting this stage of sleep. This seems to fit with the neural activity characterisation of sleepwalking. Other research groups have identified alcohol as a trigger for sleepwalking, but the evidence is less convincing here. It should be noted that the above factors, bar sleep deprivation, have not been studied in any detail in the sleep laboratory. Anecdote does not science equal but, hopefully, it will provide a springy launch-pad for future research.

So, returning to the beginning and my story of my own sleepwalking episodes as a child. Sleepwalking, like sleep itself, is a puzzling but fascinating phenomenon. It may be that children are more likely to experience sleepwalking briefly as a facet of normal sleep architecture development. This likely explains my own, admittedly hair-raising, experience. However, a definite answer for what may cause sleepwalking in adults is less certain. Further research of known triggers and improvements in eliciting somnambulism in the sleep lab will help clarify these issues. Regardless, we already have some useful clues and it is likely that slow wave sleep problems will lead us in the right direction.

No doubt sleepwalking will remain of interest to scientists, playwrights, artists and anyone who has had even a brief brush with embarrassing or benign breaks in sleep. FYI, the story I decided to share with you is the least embarrassing sleepwalking episode I could think of.

Inquisitive Tortoise

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Fresh Beginnings

210_SLEEP Heart and Brain

It has been a long time since I’ve posted anything here but I feel it’s time for me to come back at long last. For a start, I’ve finally managed to snare funding and thus I have recently (last September) started a PhD at the University of Manchester to study sleep loss in individuals with mental illness. This project is so fascinating but there is so much I feel I need to learn in order to make a worthwhile contribution. So, as part of my research, I have started answering basic sleep questions which I think will help inform my own studies and thinking. I’ve written these so that they’re accessible to everyone as I feel that’s the best way for the work to stick in my head, and also potentially make these articles useful to someone besides me.

Although I have no idea how many people will read this (if any), I will still get some benefit from educating myself more about sleep, sleep problems and the impact of both of us on our daily functioning through writing these articles. If a few people were to read and enjoy them though, I would be overjoyed (simple academic, that I am)! As a disclaimer, nothing I post here will be set in stone – medically speaking – but will be the product of my own research, conversations and (in the future) own experiments within this field. I will likely touch common sleep problems such as insomnia and sleep apnoea in the near future, and although  what I write will be as as truthful as I can manage with the available materials, this blog will be no substitute for seeing a doctor about your own concerns.

I’m looking forward to exploring sleep in more detail and answering some of the questions I had before even starting on this PhD. However, on that note, if there are any questions which people have about sleep, I am would be more than happy to give it my best go to give you a satisfying answer.

Expect the first article shortly!

Inquisitive Tortoise

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