Why We Write About Sleep

In Why we sleep (2017) Matthew Walker, a neuroscientist investigating sleep, writes about the importance of sleep for our health, mental well-being and daily functioning. Walker gives some interesting examples of empirical research on the positive effects of getting enough sleep, and the negative effects of not getting enough of it. Some of Walker’s ideas seem a bit odd, however. For instance, he writes about the shift in the circadian rhythm of older people, which makes them feel tired earlier in the evening and wake up earlier in the morning compared to younger adults. Having explained this shift, Walker recommends that older people wear sunglasses when going outside during the morning, and that they take off their sunglasses during the afternoon, in an effort to ‘push back’ their internal clock. It’s not clear why they should do that, though. Why can’t they just let their circadian rhythm run the way it does? Waking up early is not exactly a serious health hazard, is it?

While this suggestion is merely a little odd, dome of Walker’s ideas may even sound a little disturbing. In the last chapter, Walker discusses what could be done to promote healthy sleeping habits. In light of the recent discussions about big data and privacy, some of Walker’s suggestions may remind you a little too much of Big Brother, who is always watching you. For example, Walker suggests that health insurance companies could track your sleep hours and, given the health benefits of healthy sleeping, offer you a discount on your insurance fees if you slept enough hours each night. Do we really want insurance companies – or any company – to know about something as personal as our sleep habits? It may be a brave new world, in which we all live and sleep happily and healthily, but, frankly, I’d rather not live there.

In addition, the distinction between correlation and causality is not always as clear as it could be. Walker sometimes writes about longitudinal or epidemiological research, and draws conclusions from them that would require an experimental manipulation. For example, he writes about an association between insufficient sleep and an ‘overactive’ sympathetic nervous system (SNS). Walker will say that a lack of sleep will ‘over-activate’ your SNS. As you may remember, the SNS is involved in the stress reaction in your body – the so-called fight-or-flight reaction (for example: Kalat, 2012). It could be that some of the people who fail to get enough sleep are in a stressful situation – a scary deadline or exam coming up, for instance – and it is this stressful situation which keeps them awake at night, as well as activating their SNS.

Walker makes more of these errors. In one of the chapters, Walker writes about Fatal Familial Insomnia (FFI). This condition is related to Creutzfeld-Jakob disease (also known as the mad cow disease). In FFI, prions – a kind of misfolded proteins – severely and progressively damage your brain, ending in death. One of the first parts of your brain to be affected by FFI is the thalamus, which is also involved in the regulation of sleep and wakefulness. The name Fatal Familial Insomnia is no coincidence: sleep, for people with this inherited condition, will become increasingly fragmented, and during the last months of their lives, patients may get no sleep at all. Walker presents this condition as ‘evidence’ that not sleeping really ’kills.’ However, an alternative conclusion could be that having a disease which damages the entire brain – including sleep regions – kills.

Even if Walker’s conclusions aren’t always completely right, your parents were probably right in telling you about the importance of sleep, when they sent you to bed as a child. Yet Walker’s claims may sometimes seem a little too bold. While reading the book, you start looking for the salt, to take a pinch of two, or three. Readers who wish to learn about sleep may benefit more from a book that is a little more neutral and a little less zealous.

Being a professor of neuroscience and psychology, Walker really should know a thing or two about using references and yet, he rather often fails to use them. At some places, Walker’s failure to use references becomes rather problematic. One of the claims central to Walker’s book is that on average, we need eight hours of sleep. Yet nowhere does he describe any evidence showing why we need eight hours, rather than seven, for example, or nine. An argument as central to the book as this one really needs some empirical ground.

These eight hours might not be so undisputable as Walker claims they are. As another sleep researcher puts it: ‘just as it is no problem when you can’t eat a whole pizza, it is no problem if you need less sleep.’ (William Winter, in Beckers, 2019). Another researcher, Tony Fernando, puts it even more strongly: ‘That’s rubbish. You’re talking about epidemiological studies that say eight hours is important. You have to individualize it. Eight hours is fine if you’re an eight-hour person but many of us are not.’ (Raising the bar, 2019). Some people with an extremely rare gene variant can even get by on as little as four to five hours of sleep, without any negative effect on their health or functioning (Keulemans, 2019; Xing et al., 2019). So this ‘eight hour fact’ in Walker’s book is not really a fact after all.

Worryingly, there may be more of these false facts in the book. Indeed, some of the things Walker writes turn out to be plain wrong. One reviewer went on a fact-checking tour through the first chapters of the book. He looked up a number of the sources Walker mentioned but failed to refer to in his book, and found that some of their results are not quite as Walker presented them (Guzey, 2019). (Do bring your jar of salt along, as Guzey appears to have some funny ideas about ‘healthy sleep’ himself). For example, the World Health Organization (WHO) never declared a sleep loss epidemic, in spite of Walker’s claim that they did so. When asked about this discrepancy in an interview, Walker replied that, although the had not actually declared a sleep loss epidemic, a number of other declared public health concerns, such as cardiovascular disease or addiction are related to sleep. So really, sleep should be on their list, too (Awakin call editors, 2017)

One of the more odious factual errors occurs when Walker writes about sleep deprivation therapy in depression (Guzey, 2019). According to Why we sleep, thirty to forty percent of patients will feel better after sleep deprivation, but sixty to seventy percent of patients will feel worse. A meta-analysis (Boland et al., 2017) actually found approximately 45 percent of patients responded well to this treatment in RCTs, and funnily enough, Walker himself (2009) found a forty to sixty percent response rate in earlier research. The percentage of cases in which the depression worsens seems to be significantly lower than the one reported in Why we sleep: a review referred to by Walker himself in his 2009 article found this to be a mere two to seven percent of cases (Giedke & Schwärzler, 2002; Guzey, 2019).

Unfortunately, few reviews were as critical of Why we sleep as Guzey (2019). In fact, the book got some skyrocketing reviews. ‘It’s probably a little too soon to tell you that it saved my life, but it’s been an eye-opener.’, one reviewer (O’Connell, 2017) wrote. Why we sleep even became an international bestseller (claims the book cover). But not everyone was as happy about the book. That’s why Darian Leader wrote Why can’t we sleep? (2019). When it comes to Walker’s book, Leader has a few interesting points to make.

One of his points is that emphasizing the negative consequences of not getting enough sleep, is not exactly helping if you are already having a hard time getting enough sleep. As Leader (2019) writes: ‘won’t the pressure to sleep correctly actually get in the way of our sleep?’ The idea that anxieties and worries surrounding sleep may play a part in insomnia is endorsed by sleep scientists (other than Walker; see for example Beckers, 2019). As one sleep researcher puts it: ‘If you wake up in the middle of the night what you do not want to do is tell yourself “Go to sleep. You have a lecture tomorrow. Go to sleep. If you don’t sleep you will not perform well. If  you do not perform well, you will get sacked. If you get sacked, you will be homeless. If you’re homeless, you’re dead.” ’ (Tony Fernando, in: Raising the bar, 2019). So worrying about getting enough sleep may actually make it harder to get the sleep you need.

Indeed, you might wonder if Walker’s rather alarming warnings about the negative consequences of not getting enough sleep, are actually harming – rather than helping – sleep. One podcast (Insomnia Coach; Reed, 2019) interviews ‘Scott,’ who, so the podcast claims, ‘slept well his entire life until he listened to a podcast that led him to worry about how much sleep he was getting and the health consequences of insufficient sleep’ The person Scott believes he might have heard in this podcast is… Matthew Walker (Reed, 2019). Whether or not Walker truly was the person on this podcast, this story does demonstrate how a pressure to sleep enough may cause exactly those worries about sleep which could keep you awake at night.

Another interesting point made by Leader is that there’s something of a norm in the message that you need to get a specific number of sleep hours. In present-day society, many of us are striving to be ‘the best version of ourselves.’ We may feel pressure to be successful, or happy, or try to improve ourselves (see for example: van den Breemer, 2018; van Hintum, 2016). In emphasizing the importance of sleeping eight hours, this effort to improve ourselves now extends to our sleeping hours, as well as our time awake.

Some of Leader’s ideas, however, may seem a little odd themselves. One point Walker and Leader agree on, is that the sleep pattern in pre-industrial societies differed from our modern hours of extended sleep during the night. They even agree on the fact that these societies had a ‘biphasic’ sleep-pattern. But curiously enough, they don’t agree, at all, on what this biphasic pattern looked like. According to Walker, bi-phasic refers to a nap in the afternoon, and a longer period of sleep during the night. Leader defines biphasic sleep as two blocks of sleep during the night, with a few hours of wakefulness in between. (It’s hard to imagine such a pattern of sleep and wakefulness during a time when people lit their houses with (oil lamps) or candles, which may have been expensive for many people). Walker does not believe in this two-blocks-each-night sleep pattern. According to Walker: ‘anthropological studies of pre-industrial hunter-gatherers have also dispelled [this] popular myth about how humans should sleep. (…) The fact that no pre-industrial society to date demonstrates a similar nightly split-shift of sleep suggests that it is not the natural, evolutionary programmed form of human sleep.’ It’s just a pity that he, again, fails to refer to these anthropological studies that dispelled the myth, to back up his claim. Now we just have to take his word for it – and his word does not seem to be particularly reliable.

Leader does a lot better than Walker when it comes to references, although it’s not always clear which references refer to which facts. Unfortunately, Leader does not discuss a lot of empirical research in his book, and thus presents very little evidence for his claims. Leader is a psychoanalyst and many of the ideas he discusses, several based on Freud, are also psychoanalytical in nature. Some of these ideas and theories may seem overly complicated and far-fetched. If you are looking for a book with some (empirical) ‘facts’ about sleep, there’s very little to be found in Why can’t we sleep. If, however, outlandish theories and ‘alternative’ explanations of fairy tales are really your thing, then this book might still interest you.

There are many myths about sleep. For example, did you hear about the Dual Core, Everyman, Uberman, Dimaxion or Spamayl sleep schemas (Kemps, 2019)? In one of these sleep patterns, people are believed to get by on as little as two hours of sleep each day (don’t try this at home). Even without any evidence, you can imagine how such a ‘myth’ might really be harmful. But, as the story of Scott demonstrated, the myth that everyone needs eight hours of sleep can do harm, as well. Meanwhile, as Leader (2019) writes, sleep has also become big business. Companies claim to help you fall asleep by selling you the latest sleep app, a special sleep technology pillow, an audio wave headband, a relaxation course (Green, 2017), or a fancy mattress (Leader, 2019). According to Green (2017), sleep has even become a status symbol.

Sleep is probably best served by a neutral and down-to-earth summary of what we do know from empirical research. We need to debunk the theories that threaten our sleep, whether these myths are that each of us needs eight hours of sleep, or that we can make do with a mere two. Why we sleep seems to create myths around sleep, rather than explaining the empirical evidence. Why can’t we sleep is a good step towards debunking some of the more harmful myths Walker created. Unfortunately, lacking much empirical evidence, this book has some limitations of itself. This is why we need to keep writing about sleep. <<