If this is your first time reading, please check out the overview for Poor Ash’s Almanack, a free, vertically-integrated resource including a latticework of mental models, reviews/notes/analysis on books, guided learning journeys, and more.
Sleep / Rest / Chronotypes Mental Model: Executive Summary
If you only have three minutes, this introductory section will get you up to speed on the sleep / rest / chronotypes mental model.
The concept in one quote:Sleep is not an optional lifestyle luxury. Sleep is a non-negotiable biological necessity. It is Mother Nature's best attempt yet at contra-death. - Dr. Matthew Walker Click To Tweet
The concept in one sentence: most Americans believe two theories that have been rigorously dismantled by science: 1, we can do without 8 hours of sleep (we can’t). 2, we can exert control over our circadian rhythm and choose what time to go to sleep and get up (we can’t.)
Key takeaways/applications: sleep is the health and productivity intervention that nobody’s talking about: simply getting a proper night of sleep carries zero opportunity costs while boosting immune function, improving learning and memory, preventing cancer, dramatically improving empathy and productivity, and a whole host of other benefits.
Three brief examples of sleep / rest / chronotypes:
Who needs a prefrontal cortex anyway? Business managers and anyone who’s undergoing a surgery, take note: a lack of sleep can cause the prefrontal cortex – the rational, logical part of our brain – to remain in an “offline, disabled state.” If you’re sleep-deprived – as 70% of Americans, or anyone who routinely wakes up with an alarm clock, is – you’re literally working without the help of the most powerful part of your brain. Is this the condition in which we want our executives – and surgeons – making decisions?
Drowsy drivers kill more people than drunk and drugged drivers combined. This is a frightening statistic, considering that public budgets to combat drowsy driving are approximately ~1% of that to combat drunk driving.
As I explore in the culture mental model, many professions enforce a completely unscientific “tough it out” approach to sleep – despite the fact that, as Dr. Matthew Walker explains in the phenomenal book “Sleep” (Sleep review + notes), there is no substitute for sleep: not willpower, not caffeine, not nothing.
What is something true that nobody else agrees with you on? Peter Thiel’s famous “secrets” question, explored in some more depth in “Zero to One” (Z21 review + notes), is one that, for a long time, I didn’t have a pithy answer to.
And then it struck me that I did: chronotypes matter. It’s the single most important true-but-unbelieved insight I have to offer to the world after years of reading, studying, and investing for a living.
What’s a chronotype? It refers to the midpoint timing of your natural sleep cycle – colloquially known as whether you’re an “early bird” (lark) or “night owl.” Both rigorous scientific research, and my terrifying personal experience, demonstrate that your chronotype is critically important to your health and capacity to make effective decisions, as we’ll explore.
If this sounds interesting/applicable in your life, keep reading for unexpected applications and a deeper understanding of how this interacts with other mental models in the latticework.
However, if this doesn’t sound like something you need to learn right now, no worries! There’s plenty of other content on Poor Ash’s Almanack that might suit your needs. Instead, consider checking out our learning journeys, our discussion of the cognition / intuition / habit / stress, multicausality, or local vs. global optimization mental models, or our reviews of great books like “ Onward” (O review + notes), “The Design of Everyday Things” (DOET review + notes), or “Deep Survival” (DpSv review + notes).
Sleep / Chronotypes: A Salient Story
If I had to pick the easiest mental model to internalize, I’d choose salience. Over and over and over again, wherever you look, you find a consistent theme: one death is a tragedy. A million deaths are a statistic. Did you know that it took a dead President to get doctors to believe in Germ Theory? True story. I discuss that in the salience mental model.
People learn more from stories than stats, so I’m going to depart from the usual format in this model and start with a rather lengthy story. Later, we’re going to talk about the millions of people who are being killed, in cruel and unusual ways, by a lack of sleep.
But first, we’re going to talk about one person who almost died thanks to a lack of sleep. Someone I know well.
Let’s call him “Sam.” (It’s a pseudonym, as we’ll get to.) If you want to skip to the statistics, feel free to ctrl+f for “Sleep Diplomat” – I won’t mind!
So. Our bravehearted protagonist, Sam, had always been an extremely bright and hard-working young man. He competed in the National Spelling Bee five times in elementary and middle school, placing second and third. He started dual-credit courses at a community college at 13, and graduated high school four years later at 17 with two and a half years of college credit under his belt. Three years after that, he’d completed an undergraduate degree and an MBA, the former magna cum laude and the latter with a perfect GPA, winning a national essay contest, acing the GMAT, getting the top score in the world on a finance test, and placing highly in several business case competitions along the way.
After his first year of “real” college – a college senior at 18 years old – Sam was bored. Classes weren’t very interesting. So he started writing for a well-known stock market website, and then applied for an editorial position.
The website was astonished that Sam was merely one person; based on his publication frequency, they’d assumed he was a team of people. Once an officially-minted editor, despite being the only person on the staff to also be a full-time student, Sam edited about twice as many articles as the average editor, and was much-beloved by the website’s contributors for forging relationships and soliciting feedback on how to improve the site.
Sam spent a year there, then moved on to a hedge fund, where he worked as an analyst. Spectacularly balancing school and work, Sam earned 100% of his possible performance bonus during his first year at the fund.
It was during the second year that everything fell apart. It was weird – Sam had expected to feel better when he was finally done with school and had more time to relax. Instead, the opposite happened. He felt worse… and worse and worse and worse.
Sam had struggled with depression and anxiety in high school, but he’d never been this miserable. His brain was foggy – he couldn’t think for much of the day; it was like his brain was offline. He never got any work done before 3 PM, mostly just sitting at his computer pretending to work, then making it up at night when he got home (after taking a nap at the office as soon as his boss left.)
He was exhausted, all the time. Every day, he woke up groggy, and punched the snooze button until he literally barely had time to get on his clothes and get in the car.
Sam tried everything: more caffeine, less caffeine. More exercise, less exercise. Warmer room, colder room. Sleeping in a ski suit, sleeping butt-naked. Reading before bed, playing video games before bed, talking to his mom before bed. Breathing exercises. Counting sheep. Nothing really helped. He lay there in bed, awake, night after night, miserable. He was exhausted, but he couldn’t fall asleep until 2 or 3 AM, no matter what he tried, unless he took enough Benadryl to “tranquilize a horse,” as Sam’s doctor quipped.
Sam felt better on the weekends, when he frequently slept until 2 in the afternoon. It didn’t take a hedge fund analyst to see the connection. Sam asked his boss if he could work from home, or come into the office late. Sam had no coworkers and his work was not time-sensitive – if it got done today or next month, it didn’t matter.
The hedge fund didn’t trade much. It didn’t ever really trade at all, in fact. Sam’s role was sort of honorary, like he was a very expensive office accessory. Sam only talked to his boss for 15 or 20 minutes a day. Sam was a young man whose job was to read things on the internet and write reports about them. It didn’t require sitting in an expensive, ergonomic office chair at any specific time.
Sam’s boss said no. You have to come into work at 9:30, at the latest. Sam’s boss’s assistant – an extreme early bird, herself, who woke up before dawn to go running – judgmentally muttered something about “adult” this, that, or the other.
Sam shrugged and went aon. He usually showed up at 9:45 or 10:00, to his boss’s chagrin. It didn’t help. His health began to deteriorate, both physically and mentally. He was frequently sick. His body hurt all over. Some days he couldn’t control his body temperature; he’d shiver uncontrollably, even if it was bright and sunny outside. Every small, minor setback – or even loud noise – set off an amygdala hijack. Sam was basically terrified of his own shadow. Sam became convinced, for no apparent reason, that a very nice, friendly yoga instructor in a coffee shop was plotting to murder him. (Sam later learned that was called a “panic attack.”)
Sam was 21 but felt like he was 81.
He didn’t want to see his friends. He was too tired. He had trouble remembering people’s names even if they’d just introduced themselves three minutes ago. He gained a lot of weight, and not the kind that looks good in the mirror. He hated the job that he’d once been so excited and eager to go to. He hated his life. He hated himself.
He especially hated himself because nothing in his life was going right, and he was trying so very hard to do his best. But his best was never good enough. He didn’t seem to be able to make any new friends. He snapped at his family, even though they were nice, wonderful people.
His performance in his personal portfolio – and that of his family – which had once been a point of pride, went south, in a really bad way. He couldn’t think straight. He got involved in some really bad investment decisions – then doubled down, and doubled down again, as they got worse and worse.
Every time he walked down the fifth-flour hall to the bathroom, passing the balcony overlooking the atrium below, he thought about jumping.
He was sensible enough to know that wasn’t the answer. But it was a temptation.
One day, he just couldn’t take it anymore.
He was at the gym. He was trying to lift weights. He couldn’t. In fact, he couldn’t do much of anything. He sat down on the hardwood floor and cried, tears streaming down his moisture-wicking shirt onto his exposed knees.
He’d struggled before, but he’d never not been able to rise to a challenge. There was nothing Sam couldn’t do. Sam was Batman. Sam had no limits.
Sam realized, sitting there, that he did have limits. This was his limit, this right here.
Sam had been homeschooled, so for much of high school – other than the occasional debate tournament or early dual-credit class – he’d stayed up until 3 or 4 AM and woke up at 10 or 11 or noon (much to his mother’s chagrin). For much of college, he’d scheduled his classes so that they were no earlier than 10.
In other words, never before in Sam’s life had he had to wake up at 8:30 AM five days a week.
Sam read about chronic sleep deprivation. The symptoms fit him to a T. And, demonstrably, Sam was getting no more than 6 hours of sleep each weeknight – if he was lucky. This had been going on since he started working for the fund. The website editor job, that was remote – he got to sleep in, then. Now he didn’t.
Ah. There’s the difference. Sam could do anything… as long as he slept alright. Wake him up before he’s ready, though, and you might as well hire a mentally-challenged goldfish. A really ugly mentally-challenged goldfish with a bad temper, that too.
The next day, Sam struggled through his morning at work. Now his goal was just to make it to the end of the year so he could get his vested bonus, and leave.
At lunch, he sat outside in the pretty courtyard under the shady trees and read Megan McArdle’s wonderful “The Up Side of Down” (UpD review + notes). It was a book about failure. It resonated with Sam. Sam, at that moment, understood what Megan McArdle was talking about. Sam felt like a complete, total, irredeemable failure.
All Sam had ever wanted to do was make his parents proud and, as their only child, support them in their retirement – while making enough money that he could be someday a great dad to his kids, both as a provider and as a presence in their lives.
Sam had no fucking clue how he was going to do any of that now. Sam didn’t want to swear unnecessarily, but he didn’t have the emotional control to stop himself.
Sam had always been able to accomplish things with ease that other people only dreamed of – but Sam couldn’t accomplish the one thing that everyone assumed wasn’t even an accomplishment. Getting up on time to show up for work.
But what an accomplishment it was. Getting up at 8:30 A.M. day after day after day was the hardest thing Sam had ever done in his life. Nothing in his life had prepared him for that. It felt horrible, at 21, a once-budding workforce superstar, to feel like all the doors that had once seemed open were now slammed totally, completely, cruelly, irrevocably shut.
Because who the hell’s gonna hire a brilliant, hardworking kid who can’t show up at 9 AM? Nobody. Goddamn nobody, that’s who.
Everyone knows the workday is 9 to 5. It’s inflexible. It’s written in stone. It’s a rule handed down from the gods. If we started the workday at 10 – god forbid, 11 – planes would fall out of the sky. Children would die of horrible diseases. The entire moral fabric of our society would unravel and leave us screaming in agony in a postapocalyptic doomsday. There would probably be cannibalism.
Sam closed McArdle’s wonderful, wonderful book. He finished his personal pizza and can of Coca-Cola. He walked back up to the office, and – tearfully – told his boss he couldn’t do it anymore. That he couldn’t do anything anymore. That he needed to sleep. Sam told his boss he could cut his pay – anything – just let me sleep.
Sam went home and slept.
After a few days, Sam started to feel a lot better. Working from home and getting up at 10 or 11 or noon every day after a full night of sleep, he got more research done in the next month than he had in the previous ten months of the year. At a conference that month, a team of executives said he was the first investor who’d ever “gotten” their story. They were astonished to learn he was only 21. Their stock, by the way, went up by 6x over the next three years. (Sam eventually bought their stock – just not enough of it, much to his dissatisfaction.)
Sam’s boss fired him anyway. Well, not technically. Sam quit before the boss could fire him. But that’s what would have happened, had Sam not quit.
Sam wasn’t feeling any stress. It’s hard to worry about trivial stuff like that when you’re getting nine hours of sleep a night and feeling like you own the world. Sam went on – as he’d been planning to do for some time – to start a hedge fund. That hedge fund delivered phenomenal performance over the next two and a half years, and Sam was recognized by tenured industry professionals as a uniquely insightful and thoughtful investor.
Sam lost twenty pounds while gaining a bunch of muscle. Sam caught a cold maybe once every six or nine months, rather than once every six weeks. Sam was happy – very happy. He was one of the happiest people he knew, in fact. The depression was completely gone. Occasional, modest bouts of anxiety faded over time via self-applied cognitive behavioral therapy.
While running his fund, mentoring aspiring value investors, carrying stupidly heavy backpacks up stupidly tall mountains, and learning to cook, Sam put together a half-a-million-word website synthesizing the lessons from the hundreds of books he’d read with all that newfound focus, energy, and cognitive power.
Sam was back to being Batman. Sam, once again, had no limits.
Except sleep. Sleep was a limit. Sam preferred to call sleep his superpower. It’s a pretty cool superpower.
It, among other things, cures cancer, enhances cognition, and makes you more attractive to people of your preferred gender.
Wouldn’t you like to have that superpower?
The good news is you can. We all can. It’s everyone’s birthright.
Sam, of course, is someone I care about very much. If you didn’t pick up on it by, like, the second line: Sam’s me. If you’re on this website, hopefully you care about me, too.
That’s my story.
Let’s explore the science behind it.
Dr. Matthew Walker the “Sleep Diplomat”: Meet Sleep’s Scientific Superhero (And His Sidekick)
Superheroes do exist, it turns out. Dr. Matthew Walker – who calls himself the “Sleep Diplomat” – is a superhero. And his superpower, it turns out, is being phenomenally good at translating rigorous scientific research on sleep into an accessible format that non-PhDs like you and me can understand.
Walker wrote a book called “Why We Sleep” (Sleep review + notes) – available in both hardcover and paperback, as well as Kindle and audiobook – that I think is the most important book of the century. No hyperbole.
I bought copies for all Askeladden clients to celebrate the launch of Poor Ash’s Almanack. I feature his book, and a quote from his Talk at Google, in my email signature. I can’t recommend highly enough that you buy the book – multiple copies, please. Give them to your friends for Christmas. Give one to the mailman. Give one to your dog, I mean seriously, it can’t hurt.
A fuller version of the quote that started this model, from Walker’s Google Talk, is as follows:
”Sleep is not an optional lifestyle luxury. Sleep is a non-negotiable biological necessity. It is Mother Nature’s best attempt yet at contra-death. The decimation of sleep throughout industrialized nations is having a catastrophic impact on our health, our wellness, and the safety and the education of our children.
I believe it is now time for us to reclaim our right to a full night of sleep, without embarrassment, and without that terrible stigma of laziness. And in doing so, we may finally remember what it feels like to feel awake during the day.”
Or, as one researcher quoted in Walker’s book puts it, given that all animals known to man (even worms) sleep:If sleep does not serve an absolutely vital function, then it is the biggest mistake the evolutionary process has ever made. - Dr. Allan Rechtschaffen Click To Tweet
As Walker’s book explores in an engaging and fascinating way, sleep is quite possibly the largest contributor to all-cause mortality that can be easily modified at a societal level with zero opportunity costs. The value of sleep has been proven beyond reasonable doubt by over 17,000 pieces of heavily-scrutizined scientific research. We just need to build a culture that appropriately values and recognizes sleep.
For a fuller understanding of the nuances of NREM vs. REM sleep and sleep’s role across our lifetime – and its implication in various conditions – you absolutely have to check out his book.
Here, we’re going to review some of the key findings in Walker’s book, integrating them with another book – Till Roenneberg’s wonderful discussion of chronotypes, called “Internal Time” (IntTm review + notes) – as well as research by Christopher Barnes (who needs to write a book already!) – and a number of other sources I’ve read.
In order, here are brief answers to the questions you never knew you had about sleep, in FAQ format. Think about my story above – I was astonished, reading Walker’s book, to find him mention almost literally every symptom of sleep deprivation that I personally experienced.
Who is sleep deprived?
The vast majority of teenagers, 70% of adults in industrialized nations, and anyone who routinely wakes up with an alarm clock or needs coffee to feel alert and personable upon waking up. Health authorities like the CDC and the WHO call sleep loss an “epidemic.”
What does sleep do for the human body?
Pretty much everything. Walker wasn’t kidding when he called it “Mother Nature’s best attempt at contra-death.”
Sleep is essentially the structural problem solving solution to damn near everything.
– it’s critical to the function of your immune system, including recognizing and killing cancerous tumors before they get too big
– it’s more important to health, ranging from cardiovascular to diabetes to everything else, than diet or exercise – in other words, do NOT get up at 5 AM for that boot camp. If it makes you feel like you’re dying, congrats – you’re right!
– it enables high-level rational cognition and improves judgment; without sleep, our prefrontal cortex – the rational part of our brain – can remain in an “offline” and “disabled” state
– it dramatically reduces the risk of suicide, dramatically reduces the severity of mental health challenges like depression and anxiety, and may, in fact, prevent them (as well as conditions like schizophrenia) from ever developing in the first place
– it prevents Alzheimers by removing toxic metabolites from the brain,
– it improves memory and learning by consolidating long-term memories,
– it enhances creativity by linking disparate knowledge,
– It improves our empathy as measured by our ability to assess emotional states (Walker) and our niceness vs. “jerk-ness” (Barnes)
– it improves our ability to regulate our emotional state by a factor of approximately 2.5x. This leads to behavior as diverse as healthier eating (Walker) and better self-control in the workplace (Barnes, incl the integration of unpublished research on role modeling discussed here)
– it dramatically reduces stress and dramatically improves mood and well-being,
– it improves muscle gain and promotes fat loss,
– It makes us more attractive and, if we’re male, increases the size of our testicles, our sperm count (~30%), and our testosterone levels. (Now I’ve got all the guys paying more attention.)
– It makes doctors 5x less likely to make (potentially fatal) errors when treating or operating on patients,
– Proper sleep would prevent more car accidents than if we entirely eliminated all drugs and alcohol from the world. Both Walker and Christopher Barnes cite research finding that even modest sleep deprivation can be equivalent to being legally drunk from an impairment standpoint.
– it makes us more attractive (Walker) and charismatic (Barnes), as well as more open tofeedback and inspiration (Barnes)
– it also improves ethics and integrity (see Christopher Barnes’ research)
But those are, like, small benefits, right?
Hell to the NO.
– First, on immune function: merely one night of bad sleep (four hours) can reduce the count of killer T cells – the soldiers in our immune system – by 70%.
– Second, on cognition – Walker cites research that found that when students’ high school start times were delayed by merely one hour, SAT scores improved dramatically. I don’t know why Walker didn’t translate it into percentiles, but I did it for you. Scores on math improved from the 90th to the 97th percentile, and reading from the 73rd to the 99th percentile. You’d be thrilledif an expensive prep course delivered those sorts of results – and you can get them just by giving your kid an extra hour of sleep per night.
– Third, on car accidents – again, starting high school one hour later can reduce teenage traffic collisions by 70%. Among adults, we have a “natural experiment” – an A/B test – called daylight savings time. Every year, on the day we get one more or one fewer hour of sleep, there’s a ~20% impact to cardiovascular incidents (heart attacks) and a ~10% impact to car collisions.
Well, I get by on 6-7 hours of sleep just fine.
I’ve got some good news and bad news. The bad news is that you’re delusional. The good news is that it’s not your fault.
Walker explains that there is a genetic mutation that allows some people to get by on six hours of sleep, but its prevalence is vanishingly small. In terms of base rates, you’re far more likely to be struck by lightning than you are to be able to do okay on 6 hours of sleep. In any sizable group of people, the number who can sleep 6 hours a night and be fine rounds to zero.
Furthermore, Walker explains that people who are sleep-deprived don’t know they’re sleep-deprived – a bit like drunks at the bar who insist they’re good to drive. Bring them into a sleep lab, though, and measurable impairments show up on tests.
I catch up on the weekends, though!
No you don’t. You can never fully “catch up” on sleep, Walker explains – many of its benefits, like memory consolidation, are a once-or-never opportunity. You have to get proper sleep every night; you can’t deprive yourself on weekdays and catch up on the weekends (or vice versa.)
I’ve gotten used to it.
That’s a bad thing. Walker:
“[Individuals] consistently underestimated their degree of performance disability. It was a miserable predictor of how bad their performance actually, objectively was. […]
With chronic sleep restriction […] that low-level exhaustion becomes their accepted norm, or baseline. Individuals fail to recognize how their perennial state of sleep deficiency has come to compromise their mental aptitude and physical vitality, including the slow accumulation of ill health.”
Well, it’s kind of leveled out.
No it hasn’t. Research by Walker and others demonstrates that sleep deprivation is cumulative; after 10 days of sleeping six hours per night, you’re as impaired as if you’d just pulled an all-nighter. You’re well beyond legally drunk at this point. And it gets worse: there is no known point at which the detrimental effects of sleep deprivation stop accumulating. Extrapolating, by the time I quit my job, I was probably the equivalent impairment point of having pulled 3-4 all-nighters in a row…
Isn’t too much sleep bad for me, too?
Not at all – this is a myth. Walker:
“No biological mechanisms that show sleep to be in any way harmful have been discovered.”
In other words, sleep is not dose-dependent. More is better. Walker does note in his Talk at Google that there might be a point at which too much sleep – like too much water – is bad, but science hasn’t managed to find it yet. He goes on to note that there’s a correlation vs. causation problem in mortality data associated with people who sleep a lot: many of the people who are sleeping a lot are seriously or terminally ill, and obviously we sleep more when we’re ill for a variety of reasons. That doesn’t mean that the sleep is the cause of the negative health outcomes; in fact, it’s the other way around.
Anecdotally, for example, one of my friends’ family members who is struggling with advanced multiple sclerosis (MS) is currently “sleeping about 12 hours a day.” Assuming she is representative of those with her specific condition, certainly a study that included subjects like her would find a correlation between length of sleep and higher mortality, but it’s very difficult to tell a plausible story in which the sleep is the cause of her health issues – rather, it’s the other way around.
So: if you’re sleeping 16 hours a night, see your doctor. If you’re sleeping 9 or 10, congratulations – that’s awesome.
We can willpower our way through sleep deprivation.
Nope, nope, and nope again. Research demonstrates conclusively that neither willpower nor caffeine nor any other substance or technique known to man can replace the need for sleep. In fact, a lack of sleep degrades our willpower: see Barnes’ interview here, for example. Walker also notes that sleep-deprived study subjects:
“showed well over a 60 percent amplification in emotional reactivity […] without sleep […] the strong coupling between [the prefrontal cortex and amygdala] is lost.
We cannot rein in our atavistic impulses – too much emotional gas pedal (amygdala) and not enough regulatory brake (prefrontal cortex). Without the rational control given to us each night by sleep, we’re not on a neurological – and hence emotional – even keel.”
“Sleep deprivation degrades many of the key faculties required for most forms of employment.
Why, then do we overvalue employees that undervalue sleep?
[…] there remains a contrived, yet fortified, arrogance in many business cultures focused on the uselessness of sleep. It is bizarre […]
He cites lots of evidence about medical errors:
“Residents working a thirty-hour-straight shift will commit 36 percent more serious medical errors [… and make…] 460 percent more diagnostic mistakes in the intensive care unit than when well rested.
Through the course of their residency, one in five medical residents will make a sleepless-related medical error that causes significant, liable harm to a patient. One in twenty will kill a patient due to a lack of sleep.”
“McEvoy’s story of relentless work and sleep deprivation reminded me of the worst moments of my own internship and residency […]
subconsciously, I found myself minimizing the severity of a symptom or assuming that an aberrant laboratory result was an artifact rather than a sign of a serious problem.”
Willpower, similarly, cannot change our chronotype.
Chronotype? What’s a chronotype? Isn’t getting up early just a matter of discipline?
I’m SO glad you asked. No. No, it isn’t. Remember I mentioned Walker has a sidekick? I was sort of fibbing; I’m not sure that he and Till Roenneberg have ever actually met – but Till Roenneberg is an awesome guy. He is pictured at right.
The mechanism of chronotypes is a bit technical, but basically our internal rhythms are not naturally 24 hours – they’re usually longer or shorter by a little bit. They “synchronize” to a 24-hour cycle via exposure to daylight. A mathematical equation determines that those with shorter cycles become early birds, and those with longer cycles become night owls. In other words, if you put a night owl in complete darkness, their internal wake-sleep cycle might be over a ~25 hour period. If you put an early bird in complete darkness, their cycle might be over a ~23 hour period.
You can find various stats on it, but the majority of people in modern societies are “late” chronotypes… it follows a quasi-normal-ish distribution with a definite skew toward lateness. See Roenneberg’s book for more.
I explore chronotypes in some more detail in the trait adaptivity mental model, which explains why they evolved and how they got sort of knocked off-kilter. We are supposed to wake up and fall asleep with the sun, with some modest variation in either direction, but the problem is that our bodies synchronize to light, and modern lighting is basically “perpetual twilight” from our bodies’ point of view.
This means that early birds (“larks”) get earlier, and night owls get later.
This is a genetically deterministic outcome (and you know I don’t usually believe in determinism – see agency). Our chronotype is no more under our volitional control than our skin color, our sexuality, or any other biological trait.
In other words, telling someone – whether your teenager or employee – that they could get up earlier without feeling groggy if they “just tried harder” is like telling a dark-skinned woman that she can be white if she “just tries harder,” or telling your nephew that he can stop being gay and learn to appreciate the female body if he “just tries harder.”
Any sensible parent (or manager) would view the latter two statements as bizarre, unscientific, and frankly unethical: there’s wide agreement in modern society that it’s not okay to discriminate against people on the basis of their skin color or sexuality. Chronotypes, just like skin color and sexuality, are biological traits – but as a society, we’ve (errantly) come to believe the myth that they’re a matter of effort, and thus blatantly discriminate against late chronotypes, as I explore in the culture / status quo bias mental model.
“I am often asked whether we cannot get used to given working hours merely through discipline and by confining our sleep habits to certain times. The assumption inherent in this question is that the human body clock can synchronize to social cues.
I tend to find that any such questioner, who usually also displays a somewhat disdainful tone toward the weakness of late chronotypes, is an early type – someone who has never experienced the problems associated with the scallop-shaped sleep-wake behavior of late chronotypes.”
“When a night owl is forced to wake up too early, their prefrontal cortex remains in a disabled, ‘offline’ state. Like a cold engine after an early-morning start, it takes a long time before it warms up to operating temperature […]
Sadly, society treats night owls rather unfairly on two counts. First is the label of being lazy […] night owls are not owls by choice. They are bound to a delayed schedule by unavoidable DNA hardwiring. It is not their conscious fault, but rather their genetic fate.
Second is the engrained, un-level playing field of society’s work scheduling, which is strongly biased toward early start times that punish owls and favor larks. Although the situation is improving, standard employment schedules force owls into an unnatural sleep-wake rhythm…”
Most unfortunately, owls are more chronically sleep-deprived [than larks]. […] greater ill health caused by a lack of sleep therefore befalls owls, including higher rates of depression, anxiety, diabetes, cancer, heart attack, and stroke.”
In addition to these productivity consequences, there are dramatic health consequences. A substantial body of research has demonstrated that controlling for all other factors, shift workers (those who have to get up and sleep at unnatural times) have meaningfully higher incidence of pretty much all important mortality-causing health conditions.
Shift work has been labeled a “probable carcinogen” by health authorities – one level down on the scale from cigarettes and HIV. How’s that for contextualization?
Chronotypes are an area where empathy is important – because it is impossible to emotionally understand the perspective of a night owl if you are an early bird. Conversely, early birds deserve a little empathy too – if night owls stay up late with their friends, they have no problem sleeping in the next day, and they’ll feel pretty fine after a good night of sleep. Early birds, however – if they stay up past their bedtimes – tend to have a very hard time “sleeping in,” so they need to be in bed at the proper time if they want to get sufficient sleep.
As such, Roenneberg points out in “Internal Time” (IntTm review + notes) that early birds tend to be sleep deprived on the weekends (when there’s social pressure from night owls to stay up or out late), while night owls tend to be sleep deprived during weekdays (when early birds enforce unreasonably early work and school start times on night owls). Obviously early birds have the much better end of the stick, but don’t pick on your early-bird friends if they don’t want to stay up (or out) late with you. They’re not boring – they’re just tired, and they need their sleep!
But Benjamin Franklin said the early bird gets the worm, and (insert business book here) champions getting up at 5 AM!
First is that the early-bird proverbs, as Roenneberg explains, totally made sense in a pre-Industrial era. But that was before artificial light – we don’t work in the fields anymore; even if we do, sundown no longer means we lose our chance to work. Indeed, our chronotypes have gotten later and later as we’ve been using more and more lights (particularly blueish lights and computer / electronic device screens), but culture / status quo bias has kept work hours the same. This results in a strange situation: Roenneberg observes in “Internal Time” (IntTm review + notes) that:
“In view of the lateness of most people in our modern societies, one could argue that a majority of the workforce is scheduled in a permanent early shift when they work from nine to five.”
So let’s change that old proverb a little bit.The early bird doesn't get the worm. He gets cancer - and Alzheimer's, depression, a beer belly, and a disabled pre-frontal cortex - if he's fighting his night-owl chronotype, according to 17,000 rigorous studies. Click To Tweet
Second is that given the way trait adaptivity and selection pressure work, Roenneberg hypothesizes that the earlyness of the professional world *selects for* people who are early birds – in other words, many people who rise up the ranks of corporations tend to be early types, which isn’t surprising if they’re getting to use their prefrontal cortex while the night owls aren’t.
Think of me as an example – clearly I have all the necessary qualities to work my way up the corporate ladder and become an executive somewhere. Except for one: there’s no way I’d be happy or productive showing up at 9, 8, or even earlier.
So the corporate environment, by virtue of its early start times, selects against me – and anyone like me – notwithstanding our level of talent and drive, and selects for early birds, even if they’re inferior on every other useful trait. That leads to a feedback cycle – it’s intuitive, but also empiric. Research by Christopher Barnes (unpublished) indicates that leaders in organizations basically role-model and perpetuate their own preferred sleep behaviors.
So you have to use Bayesian reasoning and filter that sort of advice through the science, and what you know about your own body. I am not anti-mornings: I’m not suggesting everyone be a night owl, or everyone wake up at noon and start work after lunch, like I do. If you are a lark and you do your best work at 5 or 6 AM, absolutely please get up then.
Just don’t force the rest of us to conform to your schedule and call it universally superior or ‘moral.” (I cite Christopher Barnes’ research on institutionalized bias against late types in the culture mental model. See also Barnes’ TED Talk.)
What’s Walker’s recommendation for how businesses should operate, based on the actual science?
“everyone would be present during a core window for key interactions – say, twelve to three p.m. Yet there would be flexible tail ends either side to accommodate all individual chronotypes.
Owls could start work late (e.g., noon) and continue into the evening, giving their full force of mental capacity and physical energy to their jobs. Larks can likewise do so with early start and finish times.”
Well, okay, but my teenager’s just lazy and if he wouldn’t stay up so late playing video games and ma-
Hey, keep it PG-13. Okay, listen. Both Roenneberg and Walker address the fact that teenagers’ chronotypes are biologically the latest of any period in their life. No matter our chronotype, we tend to be earlier as little kids, much later as teenagers, and then gradually earlier as we age (which explains 5 PM senior specials, if you were wondering.) Teenagers, in fact, display symptoms of narcolepsy if you wake them up at school start times and bring them into a sleep lab (from Roenneberg’s book.)
Roenneberg and Walker thus both spend a lot of time discussing the tragic and terrible impact that early school start times are having on your teenager’s health, learning, and emotional stability. (Barnes talks about it too.)
“Asking your teenage[r] to go to bed and fall asleep at ten p.m. is the circadian equivalent of asking you, their parent, to go to sleep at seven or eight p.m.. No matter how loud you enunciate the order, no matter how much that teenager truly wishes to obey your instruction, and no matter what amount of willed effort is applied […] the circadian rhythm of a teenager will not be miraculously coaxed into a change.
Furthermore, asking that same teenager to wake up at seven the next morning and function with intellect, grace, and good mood is the equivalent of asking you, their parent, to do the same at four or five a.m.
[…] teenagers’ sleep patterns [… are] non-volitional, non-negotiable, and strongly biological. We parents would be wise to accept this fact […] and praise it, lest we wish our own children to suffer developmental brain abnormalities or force a raised risk of mental illness upon them.”
Walker goes on to note that it’s a myth that teenagers have always gotten up this early for school:
“Our children didn’t always go to school at this biologically unreasonable time. A century ago, schools in the US started at nine a.m. As a result, 95% of all children woke up without an alarm clock.
Now, the inverse is true, caused by the incessant marching back of school start times – which are in direct conflict with children’s evolutionarily preprogrammed need to be asleep during these precious, REM-sleep-rich morning hours.”
Here’s my takeaway: current school start times are essentially legalized and societally-condoned child abuse that would be wildly unacceptable to me as a parent. I was already planning to homeschool my kids; this is just one more reason to do so…
I’m a night owl working for a company that is entrenched in early-bird culture. What do I do?
A few options here.
First, take the time to understand the underlying mechanisms of chronotype entrainment (which I, unfortunately, had neither the energy nor knowledge to do when I was suffering.) Roenneberg’s book “Internal Time” (IntTm review + notes) provides all the information you need.
One of the most fascinating discussions in his book was a mention of some research in which people went camping (for science) and all of a sudden, they all woke up and fell asleep as nature intended – with the sun. There was still variation, but it was substantially more modest than is seen in the modern world.
I see this myself as an avid backpacker – whenever I’m hiking and camping, I’m pretty well able to get up 30 minutes to an hour after dawn, which is perhaps not early but certainly not 11 am or noon (which is my usual time in digital-era lighting.)
Summarizing some of the technical stuff, one of the signals for sleep onset is a hormone called “melatonin.” If you get a lot of light early in the day, that helps compress your clock, and you’ll feel sleepy earlier.
But conversely, if you get a lot of light late in the day, that extends your clock, and you’ll feel sleepy later, and not be able to fall asleep. And, frustratingly and paradoxically, research demonstrates that it’s damn-near absolutely impossible to fall asleep right before you’re supposed to fall asleep – that’s actually the hardest window in which to snooze (other than right after you wake up from a full night of sleep, for obvious reasons).
Finally, be aware that it’s not *all* light – but only blue light – that entrains the circadian rhythm. So if you can avoid blue light and look at red light instead, that helps you not delay melatonin onset. You can do this by several methods – one is to use your device’s settings to have a “night light” – Windows 10 ships with this and so does my smartphone; I believe there are also third party apps. Failing that, a pair of cheap red-tinted drugstore sunglasses would probably help a bit.
On top of all that, melatonin is often helpful for people with DSPD (“delayed sleep phase disorder” – not actually a disorder; just the medicalized term for “hi, my name’s Sam and I’m a night owl.”) I take melatonin myself; Walker claims it’s all placebo effect, but I don’t think his position is internally consistent, nor is that view consistent with the underlying causal mechanism of circadian rhythms and sleep onset, nor is it consistent with the research cited by Roenneberg on children with Smith-Magenis syndrome (where what were thought to be behavioral problems were actually caused by sleep deprivation due to an inverted melatonin rhythm – fixable by beta-blockers and melatonin at the right times.)
I take the ones at right; note that you don’t need to take the whole tablet… I usually do about a quarter or a third of one. Be aware that, as I discuss in the margin of safety mental model, the time-release ones include B6, which can be neurotoxic at high doses. There seems to be a big buffer between the pill and a dangerous dose, but I choose to just take the fast-dissolve one without B6.
So, to review, if you need to get up earlier than you want for your job:
– get as much bright light as you can early in the day. (start an herb garden and water it, or go for a walk, or something.)
– avoid as much blue light as you can after sunset
– consider taking melatonin 30 minutes to an hour before bedtime
Are these going to turn you from a dedicated night owl into a bright-eyed, bushy-tailed lark? Nope. Are they cumbersome? Yes, sometimes. But is the extra 30 minutes or hour of sleep you’ll get because of them worth it? ABSOLUTELY.
There are also these lightbox things you can use, but they sound sort of torturous and I’ve never investigated them myself.
Best of all – if you can do what I did and find a job that lets you keep hours that are more suitable to your chronotype – please try to do so, for the sake of your health. Also know that research (by Christopher Barnes) demonstrates that, unsurprisingly, night owls tend to be unbiased toward any chronotypes, whereas early birds tend to be heavily biased against late chronotypes. So try to find a boss who’s a night owl.
I know these are not always tenable options and I am so, so sorry if you are in that position. Trust me, I know how you feel.
But know this. A fun fact is that I don’t make much money running ACM right now; way less than I did working as a hedge fund analyst. Building clientele takes time. And, certainly, I’m lucky in that I don’t have a family to support, and in fact have a family situation that allows me to synergize by sharing some costs that we’d otherwise be paying separately. And my family is much happier with me now, with less money, than they were with me when I was sleep-deprived, making lots of money.
But I will tell you that even if, at scale, I ended up making half the money I did working as an analyst, I would take that trade every time and make the decision to quit and start ACM over and over and over again. My health and happiness are not worth the incremental money – it’s an easy utility /opportunity cost calculation. There’s literally no amount of money that would make up for the pain and suffering I went through. None.
What about alcohol and caffeine?
Walker says no to both. Alcohol suppresses REM sleep; caffeine also reduces the quality of sleep. I’ve never drank anyway, but Walker recommends total abstinence. As for caffeine, I’ve gone down from 3 to 2 to 1 cups of coffee per day over time and it’s definitely helped my sleep. Walker seems to recommend abstinence here too, but I love my specialty coffee and I get plenty of sleep, so, you know, live a little.
How are naps?
Tricky. They are great at the right time – Walker’s a huge fan, and cites some evidence suggesting they are cardioprotective and can enhance learning and so on – but if you take them at the wrong time, you’ll just push your sleep onset at night farther off to the right. So, I don’t feel comfortable opining briefly – just keep that in mind as a topic to really study when you read the book. Soojung-Kim Pang talks about naps too (see reference below).
Personally, I don’t really nap much right now, unless I have to get up really early for something, or if I’m sick, or something. Sleep at night is fine for me. But I will say that naps were probably the only thing standing between me and a complete nervous breakdown when I worked at my job.
If I get enough sleep, then I can work the rest of my waking hours and be fine, right?
No, not that either. Rest while awake is also important. Alex Soojung-Kim Pang’s “ Rest” ( Rest review + notes) goes into this. Please note that Soojung-Kim Pang is one of those people who doesn’t understand the science and thereby falls for the “morning trap” – he advises everyone get up early, as I take him to task for in the notes on the book – but the fact that he’s brutally wrong on that issue doesn’t mean he’s wrong about much of the rest of his work.
Soojung-Kim Pang explores how we’re often more productive and creative when we’re not working all the time; I’m not sure I believe his exact numbers, but I’ve seen plenty of research suggesting that working 60 hours a week is generally no more effective than working 40 hours – because of the opportunity costs of fatigue and burnout.
Indeed, survival experts like Laurence Gonzales highlight the importance of rest in life-or-death contexts –
In less dire circumstances, as I discuss in the product vs. packaging mental model, many famous luminaries like Darwin and the scientists who built the atomic bomb (see “The Making of the Atomic Bomb” – TMAB review + notes) were the opposite of butt-in-chair types.
They walked around, took baths, and that’s where they came up with their best ideas. And those are often what are really important – mindless busyness, as Stephen Covey puts it in “ The 7 Habits of Highly Effective People” ( 7H review + notes), is like chopping down trees in the “wrong jungle!”
Further Reading on Sleep / Rest / Chronotypes
Uh, did you read any of the circa-9,000 words before these?
Because if you did, you’re already the proud owner of a brand-spanking-new (or gently, lovingly used) copy of Dr. Matthew Walker’s “Why We Sleep” (Sleep review + notes) and Till Roenneberg’s “Internal Time” (IntTm review + notes).
Click the pictures below to buy the books if you haven’t already; the picture to the right will take you to Christopher Barnes’ homepage, where you can explore some of his research.
And send Barnes an email and encourage him to write a book…