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Pandabook Club #6: Why We Sleep

By Petra Gönczi | July 2021

Our choice for June's Pandabook Club was Why We Sleep: The New Science of Sleep and Dreams, by Matthew Walker. This title found its way onto the list as the Pandable team share a general interest in the topic of maintaining both physical and mental health, and the activity of sleeping provides the perfect intersection.

Our choice for June's Pandabook Club was Why We Sleep: The New Science of Sleep and Dreams, by Matthew Walker. This title found its way onto the list as the Pandable team share a general interest in the topic of maintaining both physical and mental health, and the activity of sleeping provides the perfect intersection. We all know that we should be practicing good 'sleep hygiene', part of which involves getting proper, efficient sleep, but Walker’s book provides arguments and data to prove how important sleep really is. The book also contains some fascinating facts about our circadian rhythms, the effects of caffeine on the body and the animal kingdom’s surprising sleeping rituals.

Let’s start with an important message: this book is not an easy read. We struggled to power through the pages in the midst of all the sometimes-deeply-scientific talk. Saying that, we also found some remarkably interesting bits we were all equally fascinated with.

Being completely honest, (which we feel we can be as the author gives their permission in the book), we did feel the urge to fall asleep almost every time we dived in to a chapter. This was most likely due to the power and complexities of the topic (try not to nod off whilst reading about sleep experiments, probably the most relaxing type of experiments in the world) and possibly because we read it in bed before going to sleep.

Walker is a good, enthusiastic writer, obviously in love with his field, but we have to say: you have to be really devoted to this topic to truly appreciate it. You’ll need more than your average biology text book to keep up. Naturally, this doesn’t take any merit away from the book, but we felt the need to be transparent about this, and to give a fair warning to the ‘average’ hobby reader, as is the majority of people on our team.

🛌 The risks of not sleeping well and not sleeping enough

Sleep takes 25-30 years from our lives — when you put it like that, it seems excessive for a second, right? As it turns out, sadly, we don’t really strive to reach this average, as more than a third of adults in many developed nations fail to obtain the recommended 7 to 9 hours of nightly sleep.

This is a serious risk that many of us knowingly or unknowingly take every day. Walkers explains the associated risks in detail, but here is our summary: if you routinely sleep less than 6 hours a night, it not only weakens your immune system, but increases your risk of certain forms of cancer, of developing Alzheimer’s disease, cardiovascular disease, stroke, and congestive heart failure. Even if you reduce your sleeping time moderately for just a week, it disrupts your blood sugar levels to such an extent that you would be classified as pre-diabetic.

A serious red flag for (almost) all of us. In short: get your sleep. If sleep feels like a burden to you, re-read the above paragraph and remind yourself that it is one of the key areas in life you should be prioritising.

😴 Circadian rhythm and sleeping leaves

Circadian rhythm, known also as the internal body clock, is something that mammals, birds and reptiles biologically have in common. Dictating our sleeping patterns, blood pressure and blood sugar as well as our overall sense alertness. This internal clock is greatly influenced by our environment and can be disrupted by things like lighting, food, mood disorders, napping, and irregular work schedules.

Walker uses the example of an experiment conducted in 1729 by French geophysicist Jean-Jaques d'Ortous de Marian to demonstrate that a living organism is able to keep its own time and not necessarily according to the sun’s commands. The experiment looked at leaf movements depending on plant species, the plant which intrigued the geophysicist the most was called Mimosa pudica. It was recorded that the plant opened its leaves in the daylight and closed them at the end of the day, but through further experimentation, de Marian showed that it does the same when put in a sealed box, away from sunlight. Therefore, proving that Mimosa pudica can actually have a self-generated rhythm, not just a simple circadian rhythm. Charles Darwin later went on to call this process 'sleeping leaves'.

Interestingly, over 200 years later in 1938, it was discovered in Mammoth Cave, Kentucky, during an experiment lasting 6 weeks in which a Professor and his research assistant (Kleitman and Richardson) took a trip to one of the deepest caverns on the planet to see how the body would react to being cut off from the natural cycle of light and dark. The experiment showed that humans were also able to adapt to the lack of sun movements and changes in light and dark cycles, and proved the same argument as de Marian's sleeping leaves: we can generate our own circadian rhythm as well.

We also learned from the book that our circadian rhythm changes throughout our lives. One particularly contentious period is during the teenage years, when parents and their children fight over what time they should go to bed. Walker suggests approaching this situation with caution: the teenager is not fighting about not wanting to go to bed at 9pm because they don’t want to, they simply cannot. To be more specific: their circadian rhythm is different from that of their parents in their more mature adult years, and even if they went to bed at the requested hour, they likely wouldn't be able to fall asleep until later at night because they are literally programmed not to.

Parents are, of course, only trying to be responsible adults, knowing that the alarm clock will go off early in the morning regardless, but perhaps knowing this will reduce the amount of bedtime agro. We know all too well that today's modern habits and society don't wait for those who sleep in.

⏰ Sleep efficiency and sleep patterns: The war of biology and culture

The levels of efficiency when it comes to sleeping time also differs depending on what stage we are at in life. The sleep efficiency of a teenager, for example, is around 90% or above, while those in their much senior years (80's) see a decline in sleep efficiency, closer to 70-80%. This might not seem like too much of a jump, but in reality this equates to spending at least 1-1.5 hours awake every night in your older age. This is without the consideration of sleeping pills, caffeine or other drugs that can disturb our body's natural ability to function, often with long-lasting effects (more on this in the next section).

Our biology and the so-called 'modern cultures' and societies we have adopted around the world, have been battling against each other for a long time now, and this fight even has an influence on our sleeping patterns. We know all too well that today's culture doesn't wait for those who sleep in. Walker discusses that today we follow a something called a 'monophasic sleep pattern': we sleep once a day and in one long stretch at night. However, we have a deeply rooted biological 'biphasic pattern' that instinctively also directs us to sleep (sometimes) in the afternoon as well.

We all know that feeling, right around the time when you feel sleepy after lunch, or a couple of hours later when an unexplainable drowsiness consumes you, and you find yourself yawning away at your desk. This urge is absolutely natural and there are only a few remaining siesta cultures in the world: in South America and Mediterranean Europe where people give in to that need to rest (and even there, it’s mostly explained (or excused) by the rising heat, rather than our natural biphasic sleep pattern).

In our modern-day societies, we have all but said goodbye to this biphasic pattern of sleep and as Walker reminds us, we don’t even notice that midnight is no longer the 'middle-of-the-night' either. The average 21st century worker usually goes to bed at this time (12am), and considers it the start of the night. The problem is that we haven't shifted our daily habits around when we start our days in relation to this. The result of which means we have formed a habit of going to bed (sleep) very late and waking up just as early as if we were going to bed at 9am, meaning that we're simply not getting enough sleep.

☕ Caffeine, its effect on humans… and spiders

In case you were wondering, Walker doesn’t recommend you to turn to any artificial substances when it comes to improving your sleep or extending your waking hours, as these will influence your natural cycles.

In the book, Walker points to the fact that caffeine has an average half-life of 5-7 hours: this is how long it takes for the body to remove just 50% of its concentration, and this is only the average half-life time. This can vary greatly based on how your body reacts to caffeine (it is removed by an enzyme in your liver, the process of which is different from person to person due to genetics).

This explains why some of us cannot drink a cup of coffee early afternoon, not unless we want spend the night counting the corners of the room unable to fall asleep. So, if it takes 5-7 hours on average for half of the caffeine dose to leave your body, imagine how long it takes for its full effect to wear off, and what happens to you (and your precious sleep) if you drink more than one cup of coffee a day. Coffee is a beautiful plant and drink, but be responsible when drinking it, or consuming caffeine in any other form, for your own sake. Many of the team at Pandable only drink decaf coffee, all of the flavour and none of the anxious shakes!

Walker also mentions a strikingly interesting experiment from the 1980's conducted on this subject; a powerful example from the animal kingdom. NASA's scientists exposed spiders to a number of different drugs and monitored the effects on their web spinning abilities. When given caffeine, the spiders were absolutely incapable of constructing anything resembling a normal or logical web that would be of any functional use. Caffeine produced, by far, the worst results in the experiment, even compared to other potent drugs that were tested, which included LSD, speed and marijuana. Need we say more?

🐦 🐬 Animals are better at sleeping and dreaming than humans

Many species of animal seem to be considerably better performers when it comes to either sleeping hours or the ways of sleeping.

  • Guinea pigs sleep for an average of 9.4 hours, squirrels 15.9 hours, opossums 18 hours and the brown bat 19 hours per day. Granted, our daily duties might differ from theirs, but these are some good pointers for all of us, considering that many people don’t even scratch the surface of the recommended daily 7 hours of sleep, which is the bottom line for the average human.
  • Dolphins can uncouple the two sides of their brains, with one side remaining awake and one snoozing away, this is known as unihemispheric sleep. In this state, dolphins are capable of some movements and vocalised communication. Birds are also capable of unihemispheric sleep, but they use it in a slightly different way to dolphins. Whilst one side of their brain sleeps, birds are able to keep one eye (the eye that corresponds to the side of the brain that remains awake) open to look out for danger. This is imperative to maintaining vigilance to environmental threats whilst also getting their much-needed rest. For example, when a flock is sleeping in a line, they have two guarding birds on both ends utilising this way of sleeping: one bird has one side of the brain switched on and the bird on the other end mirrors this, ensuring they have panoramic protection. At some point they switch, allowing the other half of their brains to sleep whilst the other is awake and the corresponding eye watches over them.
  • Some animals also endure sleep deprivation much better than we or other species do. Take killer whales as an example: birth or 'calving' normally takes place away from their familial environment, or pods, and upon their return to safety neither the mother nor the calf get any sleep due to the dangerous ocean journey back to their families.
  • Birds in transoceanic migration perform similarly, and were shown to power through their journeys with periods of sleep lasting only for seconds.

💤 REM and NREM Sleep - what are they and what's the difference?

The book also discusses everything there is to know about NREM and REM sleep. NREM sleep solidifies memories, and REM sleep takes what we have learned and applies it to our experiences stored in our memory.

Interestingly, while REM sleep is operating a sort of cherry-picking algorithm, mixing our preexisting knowledge and new experiences, our bodies become paralysed. This is a sort of intervention from Mother Nature, her way of keeping safe and stopping us from acting out anything that happens in our dreams.

Why We Sleep is filled with interesting facts like this about sleeping and dreaming, so many in fact that it would be impossible to cover all of them in a single review article.

If you pick up the book, you’ll also learn about the connections between sleeping and creativity and the stories of how Paul McCartney literally dreamt up the song ‘Yesterday’, or how the same happened with Keith Richards and the song ‘Satisfaction’. You also get a glimpse into what Walker describes as the next possible step of evolution: lucid dreamers, those who are aware of their dreaming, capable of communicating with the outside world while asleep.

The world of sleeping and dreaming is absolutely fascinating. If you're interested in the human body, and you're not afraid of a few bamboozling facts and some science talk, then this book is definitely for you.

If we can give you just one key takeaway from this book, it's this: whatever big decisions are ahead of you in the future, don’t forget to ‘sleep on it’ - as Walker points out, this saying is used in many languages across the globe and now we certainly know why.

Our Pandabook for July: Dan Heath: Upstream: How to solve problems before they happen