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Sleep Pressure

Sarah-Louise Waters • Feb 14, 2021

There are two main biological drives for sleep. The first (in no particular order), our circadian rhythm, has been explained in a previous blog post (see below for a link to this post). The second is called sleep pressure (also known as sleep drive or the sleep homeostat). This blog post is all about sleep pressure, how it works and how we can work with it to get the most from our night’s slumber.


Interesting Point:

“Sleep Pressure” is nothing to do with the pressure you put on yourself when you know you should be sleeping but you can’t. However, this kind of performance anxiety surrounding sleep can be a real problem. If you believe you suffer with this type of insomnia, please contact me for more information about how sleep coaching can help you.


In simplistic terms, our circadian rhythm determines at what point in the day (when) we sleep and our sleep drive controls how much sleep we need. In this way, sleep is to sleep pressure what food is to hunger - it satiates an essential need within us. In terms of this same analogy, our circadian rhythm would be our regular daily meal times. 


We get our best, most balanced sleep when both of these biological drives align, i.e. when we are both driven to sleep because we are “hungry” for it and because it is our usual bedtime. One drive can over-rule the other, and when this happens the quality of our sleep tends to suffer as a result. 


Jet lag is a good example of when our circadian rhythm overrules our sleep pressure - it may be bedtime in our new time zone and we may have built up a lot of sleep pressure by spending a full 16 hours awake travelling, but we are wide awake and unable to sleep even in the dead of night. The reverse of this would be when we ignore high levels of sleep pressure, stay up all night studying or partying and build up so much sleep pressure that it allows us to fall asleep even in the middle of the following day. 


Sleep pressure is due to the build up in the brain of a chemical called adenosine. From the moment we wake up, the amount of adenosine within us increases hour on hour. When there are low levels of adenosine in the brain we feel alert. When adenosine levels are high, we feel sleepy. Therefore, the longer we are awake, the greater our drive/need/desire for sleep is, in the same way as the longer it is since we have eaten, the hungrier we are. 


If adenosine levels are very high, we can become disorientated, have hallucinations and experience micro-sleeps (when our eyes close and we fall asleep for a split-second). In most circumstances these tiny instances of sleep are harmless, but if they occur whilst you are driving they can be deadly. Micro-sleeps account for around 20% or one fifth of all road traffic accidents in the UK.


During sleep your brain degrades and removes the day’s build up of adenosine. Therefore, when we have sufficient good quality sleep at the end of a day, we release all of that sleep pressure overnight and can begin again with a level of zero the next day. If we don’t have enough sleep or the sleep we get is not of a good quality, we only release some of that sleep pressure and retain the rest. This left over sleep pressure will then build up again during the day and roll over night after night, leaving you with chronic fatigue and all the health problems related to sleep deprivation.


When we retain sleep pressure we wake up feeling tired, groggy and struggle to stay alert. On those days most people will reach for an extra dose of caffeine. This is because caffeine blocks the effects of adenosine on the brain meaning that you can continue to feel alert even with the presence of high levels of adenosine. In another blog we will take a deeper look into the sleep-damaging effects of caffeine and how easy it is to get caught in a “caffeine=sleep deprivation=more caffeine” cycle. 


As stated earlier, we obtain the longest good quality sleep when our circadian rhythm is in synch and we have sufficient sleep pressure. Apart from allowing ourselves enough time between rising and our next bedtime, we can also encourage the build up of sleep pressure by engaging in physical and mental activity. The more active we have been in a day, the greater our levels of adenosine and sleep pressure and therefore the more tired we feel. Imagine the difference in how quickly and easily we fall asleep after a full day of working in the garden or your first day on a new job, as opposed to a duvet day watching movies in your pyjamas.


There is also a seemingly innocent habit that some people fall into that can have both positive and negative impacts on our levels of sleep pressure and how it affects us - napping. If you have not managed a full night’s sleep and are feeling tired during the day, you may feel better if you release the unusually high level of sleep pressure in your system by taking a short nap. In fact it has been shown that quick bursts of sleep can improve your concentration and productivity at work immensely.  


However, if you find it difficult to fall asleep at night or if you suffer with prolonged nighttime awakenings, napping during the day (and even falling asleep in front of the TV in the evening) may be contributing to this. By releasing your built up sleep pressure with a nap, it may be that you do not then build enough of it up again in order to feel sleepy at bedtime or to ensure that you fall into the deeper levels of sleep and achieve consistent slumber.


Top Tip:

If you do need to nap, ensure that you only sleep for a maximum of 20 minutes and that you are awake again at least 5 hours before your bedtime.


Our bodies and brains are remarkable machines that work best when all of our systems are in balance and harmony. If you are struggling either to be alert during the day or asleep at night (or vice versa if you’re working night shifts) and would like some help to regain your balance, please contact me for more information on how sleep coaching could help you.



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Additional Reading


Circadian Rhythm https://www.fromsoultosole.co.uk/circadian-rhythm

Sleep Cycles https://www.fromsoultosole.co.uk/sleep-cycles

How reading before bed improves sleep

By Sarah-Louise Waters • 30 Jan, 2022
Reading is an amazing way of escaping from your own reality. When we become absorbed in a story that is not our own, whether that be via a book or a movie, we put aside our own moods, worries and emotions. The more empathic we are, the more we are able to put ourselves into the shoes of the characters and let go of our own personal narrative. The benefits of doing this before settling down to sleep, especially for us highly-sensitive empaths, are immense. The ease by which we can fall asleep, the depth of that sleep and its length are all governed by how "safe" our brains feel at the time. If we are stressed, currently going though an emotional or practical upheaval, or are generally finding it difficult to switch off from the day, then our brain is going to want to keep us awake in order to continue its processing. Annoying as it is, this is simply your subconscious' way of sifting through data, resolving problems and (hopefully!) finding solutions. While nothing will ever truly be a better option than dealing with whatever is stressing you out in daylight hours, it would be ridiculous to think that there will never be a time that you go to bed with something on your mind, and this is especially true for highly sensitive, empathic individuals. Reading a book (even for a short space of time) can offer you the distraction that you need to put this issue to one-side and drift off. There are however some rules to remember when it comes to pre-sleep reading, particularly with regards to the content of what you read... 1) The topic should be interesting enough to capture your attention and stop you thinking about your worries. A text book may work, but only if you can actually concentrate on what you are reading without your brain wandering off on a tangent. 2) Reading about something you find emotionally disturbing (murder, rape, child abuse etc) will raise your blood pressure and heart rate, both of which are detrimental to sleeping well. 3) Reading a thrilling page-turner may lead you to still being awake at 2am because you just want to finish the next chapter, and the next, and the next (you get the idea!). 4) Picking a favourite book that you've already read can be a great idea - it will give you all the feels and distraction, without the need to continually page-turn as you already know what's coming. 5) If you find reading difficult because you are sight-impaired, dyslexic or have another form of reading difficulty, or simply because reading reminds you of an academic past you would rather forget, listen to an audiobook instead. You're still getting all of the sleep advantages of reading, but without the discomfort. 6) Never read anything related to your work just before bed. Reading should be about distancing yourself from stress, not inviting it in. 7) Be aware that reading on an electronic device means subjecting yourself to additional cues that now is not the right time for sleep (i.e. blue light exposure). Kindles don't smell or feel as good as a proper book either! If you are finding it difficult to fall asleep and would like some further help in the form of some sleep coaching sessions, please click on the button below and I will get back to you as soon as possible. 

Caffeine & Sleep

By Sarah-Louise Waters • 03 May, 2021
“Caffeine is the most widely used (and abused) psychoactive stimulant in the world.” (Walker, Why We Sleep, 2017) Introduction 80% of the world’s population consume caffeine in one form or another and coffee is the second most traded substance in the world, second only to oil. Our love affair with caffeine stretches around the globe and has done for centuries. Most people will have a basic understanding that caffeine has a negative effect on sleep, but this blog post has been written to better inform readers about how caffeine works and to try to help individuals reassess their current “need” for caffeine. Before I begin I would just like to clarify that I am not judging anyone for their use of caffeine. This blog post is not an attempt to guilt you into giving up something that you enjoy. What it is asking you to do is to reassess your current use and the reasons why you use caffeine. If you actually “need” caffeine to get you through the day then you should probably come clean and admit to yourself why. Mostly people use caffeine to bolster low energy levels and they have low energy levels because they have not slept well enough or for long enough the night before. If this is the case for you then I would recommend that you sort out your sleep issues first rather than simply papering over the cracks with another cup of coffee. What is caffeine? Caffeine is a psychoactive drug classified as a stimulant because it speeds up the central nervous system and increases neural activity in the brain. Other psychoactive stimulant drugs include amphetamine (speed), cocaine and nicotine. Caffeine is a naturally occurring chemical present in cocoa, coffee, cola and most teas. Below I have listed the most common foods and drinks that contain caffeine and their caffeine content. For the sake of easy comparison, I have adjusted them so that they are all per 100ml or 100gm. However, please remember that we do not always consume 100ml/gm of a product and therefore the amount of caffeine you are ingesting will vary depending on the size of the mug/chocolate bar/can etc. For example, a Starbucks Grande coffee is nearly half a litre (473ml) and contains 330mg of caffeine! Interesting Fact Plants use caffeine as a natural pesticide as it is highly toxic to most insects. It is also worth noting that the caffeine content of tea and coffee will vary greatly depending on how long you leave the drink to brew. In the table below, the tea was left to brew for one minute. If you prefer a stronger cup, the amount of caffeine in that drink will be higher.
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