Why We Sleep

If you are lucky enough to live to 79 (the global average lifespan) you will have spent around 25 of those years (roughly one third of your entire life) asleep.

It comes as no surprise therefore that from antiquity till today, thinkers and philosophers have pondered on the reason and meaning of this periodic state of rest and inactivity our species engages in.  Aristotle himself noted that, “With regard to sleep and waking, we must consider what they are: whether they are peculiar to soul or to body, or common to both; and if common, to what part of soul or body they appertain: further, from what cause it arises that they are attributes of animals, and whether all animals share in them both, or some partake of the one only, others of the other only, or some partake of neither and some of both….” (On Sleep & Sleeplessness, Aristotle c.350BCE)

Even contemporary philosophers such as Henry W. Johnstone. Jr ponder how, “…we do not normally think of sleep as necessary to human life. To be sure, it is a biological necessity, but it does not seem necessary in the way, for example, in which language is necessary. A being in whose life no language of any sort had a place could not be a human being; but can we not imagine human beings in whose life sleep has no place? Sleep seems accidental to man in a way in which language does not. Perhaps a pill can be developed that will eliminate man’s need for sleep, but no pill could be developed to eliminate man’s need for language, because if it did that, it would also eliminate his humanity…” (Toward a Philosophy of Sleep, Philosophy and Phenomenological Research, Vol. 34, Sep, 1973)

Scientific advances over the past quarter of a century have created a renaissance in sleep research, giving us greater insights into the role and importance of sleep in our lives.   To learn more, I spoke to Dr. Matthew Walker, Professor of Neuroscience and Founder & Director of The Center for Human Sleep Science at the University of California, Berkeley.

Q: Why do we sleep?

[Dr. Matthew Walker]: Even just 20 years ago we used to ask the question, ‘why do we sleep?’ It was one of the last great scientific mysteries; and the crass answer (at that point) was that we slept, to cure sleepiness. Much like saying we eat to cure hunger, however, this tells us nothing of the physiological functions that food and nutrition provide.

Today, we now have over 30,000 studies revealing a vast constellation of nighttime benefits that sleep provide. So much so, that we’re now forced to ask the question, “is there is anything that sleep does not improve?”. The answer seems to be, “no”. Every single process in the body, and every operation of the brain, is powerfully enhanced when we get sleep, and demonstrably impaired when we don’t get enough sleep.

Q:  When did it become uncool to sleep?

[Dr. Matthew Walker]: Sleep has an image problem, we have a machismo attitude that means that not only do we fail to get enough sleep, but we actually feel as though we want to wear our badge of sleep deprivation like a lapel pin that we’re proud of.  There’s a terrible stigma around getting enough sleep, some people think it’s lazy …and that’s strange; none of us would look at an infant sleeping during the day and say, ‘what a lazy baby…’ we understand that sleep is vitally important at that time of life. But soon after, we abandon the notion that sleep is essential, and instead, may even chastise others for getting enough. We even know from the research that this sleep neglect is being passed on to younger and younger people, and has impact on health and wellbeing well-into adult life.

I’ve tried to understand why sleep has this image problem, and there’s a number of reasons.  Perhaps top of the list; status.  A lot of people in society understandably want to feel important, and one of the ways you do this is to show people how busy you are… and one of the ways you show people how busy you are is to describe how little time you have for sleep… ‘I’m just so busy, I’ve got so much to do, I don’t have time to sleep….

Q: What is the impact of not sleeping enough?

[Dr Matthew Walker]:  Limiting sleep to just 4-5 hours for one single night will drop levels of critical anti-cancer fighting cells, called natural killer cells, by 70%. That’s a rather alarming state of immune deficiency, and it happens after just one night of short sleep. You want a virile set of those immune assassins at all times, and if you don’t sleep enough, you simply will not have them.  

Sleep deprivation also impacts you at a genetic level.  One study took a group of otherwise healthy adults, and limited them to 6 hours of sleep a day for a week. There were two critical findings. First, a sizable 711 genes were distorted in their activity, relative to when these same individuals were getting at least 8 hours of sleep.  This is extremely relevant, since we know that almost 50% of all adults in developed nations are struggling to survive on 6 hours or less of sleep.  Second, about half those distorted were increasing in their activity, while the other half were decreased. Genes that were decreased in activity were those associated with the immune system. Genes that were increased, or over-expressed, were those linked to the production of tumors, those associated with chronic-inflammation, and several associated with stress and cardiovascular disease.  Lack of sleep is like a broken water pipe in your home, it leaks water into every nook and cranny, and erodes the fabric of your DNA nucleic alphabet that spells out your daily health narrative.

Another experiment, performed on 1.6 billion people in 70 countries, each and every year looks at a loss of just 1 hour of sleep.  That experiment is called daylight savings.  In the spring, when we lose an hour of sleep, we observe a consequential 24% increase in heart attacks the following day.  In the Autumn, when we gain an hour, we see a corresponding 21% reduction in heart attacks.  It’s a clear bi-directional relationship. That shows how vulnerable we are to the loss of even 1 hour of sleep.  The same relationship has been observed with suicide rates; going up after the Spring 1-hour of sleep loss, and down in the autumn after the increase in sleep. An equivalent pater is seen with car crashes.

Q:  How can we cope with time zone changes?

[Dr. Matthew Walker]: You cannot cure jetlag, but you can treat it with these five hacks.

Firstly; upon arrival in the new time zone, take melatonin around 45 minutes before your desired sleep time. This will help your body regulate the timing of sleep.  Many cabin crew and pilots use this strategy.

Secondly; when you’re on a plane, in flight, you need to sleep at the right time.  If I’m flying from San Francisco back home to the United Kingdom, I’ll leave around 5pm Pacific Time and arrive around 10am London time.  Most people will probably only sleep in the last 2-3 hours of the flight (7-10am London time).  That won’t work; when you get to the UK, it’s as if you slept late until 10am, and when it’s time to go to bed later that evening at say 10-11pm, you won’t have built up enough healthy sleep pressure. As a result, you won’t feel tired enough to fall or stay asleep that first night—and the first night is key.  As a rule of thumb,  think about the time you want to go to bed in your new time-zone, and count back 12-14 hours.  You need at least that amount of sustained time awake before you sleep to have enough sleep pressure to fall asleep easily. In other words, I need to try and get a few hours of sleep in the first half of the flight, not the last half. Taking melatonin a few hours after taking off will help me advance my sleep schedule and fall asleep in the first half of the flight.

Thirdly; avoid alcohol and caffeine in flight (both of which are served liberally on planes), and for alcohol, in the first few days upon arrival. They will disrupt your body clock and make it even harder to reset to your new time zone.

Fourth; you need to get at least 30 minutes of daylight exposure, preferably before 10am, on the few days after you arrive.  Even a dull day is good enough.  If it’s a bright-day, wear sun screen or a hat, but *don’t* wear sunglasses at that time of the morning. You need the light to hit your eyes to help reset your body clock quicker.  Reverse this trick later in the day—make sure you put the shades on in the afternoon, and avoid caffeine after midday. Then get as much darkness in the evening as you can by dimming down half the lights around you, not looking at screens in the last hour, and don’t forget your melatonin dose if you have it.

Fifth; exercise and food. You need to make sure you eat meals at the same regular times as others in your new time zone.  Don’t just eat when you’re hungry, eat when everyone else does.  Regularized food intake is a powerful trigger for resetting your body clock.  Exercise also makes a difference. Try to exercise in the morning or early afternoon.

It takes around 1 day to produce a 1 hour shift in your biological clock.  If I’m crossing 8 hours of time zones from California to the United Kingdom for example, it will take about 8 days for my body to acclimate, though the above tricks can speed that up significantly.

Q:  What is the relationship between technology and sleep?

[Dr. Matthew Walker]: Over the past five years, we’ve seen the invasion of technology to our bedrooms. It certainly has had an impact in a variety of ways. But I’m not a prude in this sense. I realise that the genie of technology is out of the bottle, and it’s not going back in.  We need instead to look at how new technology can fix the ills of old technologies.

I like the idea of sleep tracking and self-quantified health.  In medicine, we have a saying: ‘what gets measured, gets managed…’ – I could ask you how you slept last night and you could easily tell me. But what if I asked you how you slept last Wednesday? Or three weeks ago on Tuesday? You will have no idea.  Sleep tracking helps us see patterns of activity, and identify problems in behavior, detrimental working profiles, physical or relationships issues that are impacting our sleep, even environmental triggers, such as temperature or light. If we can track and understand our sleep patterns, we have the chance to correct them.  We’re not quite there in terms of accuracy, but in 3-5 years, we will have laboratory-grade sensors and tracking in the palm of our hand.

I predict the connected home will be revolutionary for the sleep movement.  We are a dark-deprived society in this modern era, and we need darkness for the release of melatonin for healthy sleep.  Without melatonin, we will not sleep sufficiently.  Imagine that your smart home knows when you’re going to bed, and starts to desaturate the blue light from your smart bulbs 2 hours before. This makes sure you’re being bathed in dim yellow, not blue light.  Melatonin can be encouraged, not blocked. Society could start sleeping somewhat better.

Technology can also help us regulate our temperature, another big problem.  Constant internal temperature will prevent us sleeping and most people set their thermostat way to high.  Most people need their room to be at around 15-17C (60-65f) to sleep well, you need the cold because your body needs to drop core temperature by around 1C to initiate sleep.  That’s why you will always sleep more easily in a room that is too cold than too hot.

I am hopeful that technology will reconnect us with natural sleep, combating the way that it has dislocated us from it with the first iteration… It was, in some ways, Thomas Edison that began this.  For the first time, with the Edison Light Company, human beings controlled when it was light and when it was dark on a large-scale societal level.  We used to be at the behest of the rotation of our planet around the sun. Edison did away with that.  Arguably, this is when our sleep problems with technology probably really began.  

Q: What is the impact of sleep deprivation to our society? 

[Dr. Matthew Walker]: It is a fallacy that less sleep = more productivity.  It wasn’t true during the industrial era, and it certainly isn’t true in the digital, knowledge era.  After being awake for 18-20 hours straight (e.g., just having 5-6 hours sleep), you are as cognitively impaired as you would be if legally drunk.  I can’t think of any employer saying, ‘I’ve got this fantastic employee, they’re drunk all the time!’ – but we laud the airport warrior who has just flown through 5 time zones, who is on email until 1am and back in the office at 5am.

In studies that we and other scientists have done, the data shows that under-slept employees (those getting 6 hours of sleep or less per night) select less challenging problems.  They are much more likely to passively check voicemails and emails, for example, rather than dig deep into meaningful project work.  They are also less creative, exert less effort when working in teams, and end up exhibiting behaviours we call social loafing (i.e., slacking off and letting others do the hard work).  We’ve also found that the less sleep an employee has, the more deviant and unethical they are—the more likely to lie, falsify data and misappropriate someone else’s work as their own.  It’s not just employees; we’ve found that a lack of sleep goes all the way to the top, affecting our business leaders. For example, the more or less sleep that a CEO has had from one night to the next, the more or less charismatic their employees rate that business leader from one day to the next- even though their employees know nothing about how much they have slept. It’s evidential in their behaviour.

The RAND corporation conducted a survey focused on the cost implications of a lack of sleep. They found that insufficient sleep lead to chronic exhaustion, poor performance, and higher healthcare burdens.  The cost of sleep deprivation to most developed nations was around 2% of GDP; which is non-trivial:  $411 billion in the United States, $50 billion in the UK, $138 billion in Japan.  In other words, if you solved the sleep deprivation crisis in the workplace, you could double education budgets in most developed countries, or half the healthcare deficit.

We also know employees who sleep 6 hours or less are 63% more likely to have diabetes, 190% more likely to develop hypertension, 110% more likely to suffer depression and will take (on average) more than 11.5 extra days of sick leave a year- that’s a staggering loss of productivity.

Sleep is the next frontier of health and wellbeing productivity but most organisations simply do not know enough about it.  People talk about exercise, diet and many other workplace health and wellbeing initiatives, but sleep is the neglected stepsister of the healthcare conversation.

I’ve recently established a new enterprise that performs comprehensive evaluations of over 40 key sleep/wake metrics across a company’s workforce. We anonymously map the sleep/wake features of individuals, and in doing so, developing an entire sleep atlas of a corporation. We perform statistical analyses that surface key insights. From these analytics, we create a personalised “sleep prescription” for each individual, and writ large, a set of actionable solutions at the company-wide level.

For any C-level individual, think of sleep as the very best form of physiologically injected venture capital that your business could ever wish for. To neglect it puts you at a strategic disadvantage.

Sleep is the tide that will raise all of those other performance and health boats. It is the one lever that if you pull it, all other levels are turned up as a consequence.  I used to say that sleep was the third pillar of health and wellness, alongside diet and exercise.  the data no longer supports that statement. Instead, sleep is the foundation on which those two other bastions of health sit.

Q: What would a world be like where everyone had enough sleep?

[Dr. Matthew Walker]: Resplendent. If we all slept the correct amount (7-9 hours a night) we would increase our lifespans.  A recent study showed that people who sleep 5 hours a night have a 65% increased mortality risk- in other words, they’re 65% more likely to die at any moment in time- which is striking.

Better still, if we slept more, we would not just increase our lifespans- we would increase our health spans.  We are living longer, but are doing so in poorer health. Sleep would be a solution to this mismatch.  Sleep is nature’s best effort yet at immortality. It is unwise to neglect it.

If we all slept enough? …our healthcare burden would plummet, we would have better mental health and fewer suicides… our business would be more productive, global economies would be healthier, our roads would be safer and our children would be smarter (they would develop their brains more completely in childhood).  We would lower our lifetime risks of common mortality issues, we would have happier relationships and healthier marriages physically and psychologically.

In Summary, sleep is the very best health insurance policy you could ever wish for- and for the most part, it is democratically and freely available universal healthcare plan; one that is rather painless yet extraordinarily effective.

This is my vision; and my fervent mission.

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