Myths about “night owls” and the more useful concept of social jetlag.

It’s my goal to help you enjoy your work and in this article I want to talk about sleep. Why sleep? Because you could have the best job in the world but if your sleep sucks, you’re not going to have many happy days at work. This is a long article that covers a decent amount of theory. If you don’t have time nor interest, you can skip to the practical tools by clicking here, I definitely won’t judge you for skipping. For those wanting to get nerdy, learn some new words, and look at graphs, let’s get into it 😀

Night owls and morning larks: What exactly are chronotypes?

You’ve likely heard of night owls and morning larks, the people who go to bed very late or very early, respectively. These are generally the two categories people put themselves into, which is odd, considering that night owls and morning larks put together make up only a small portion of the population. So what are the rest of the people? Well some of you may have heard the term “third bird” but actually, when you get into scientific literature, these 3 bird identities that people seem to love, do more damage than good. Before I get into that, let’s take a look at the non-bird terms our scientist friends use.

Unshockingly, people don’t fit into just a few categories, they fall somewhere on a normal distribution of sleep times. The time you naturally fall asleep and wake-up (without an alarm clock) is what the science-y folk call your chronotype. A database of almost 300,000 people’s sleep data gives us this nice chart of average bedtimes:

Frequency in the population (%) of different chronotypes by bedtime:

• Extremely early (7-9pm) = 1.2%
• Moderately early (9:30-10pm) = 5.9%
• Slightly early (10:30-11pm) = 22.3%
• Intermediate (11:30pm-12:00am) = 29.8%
• Slightly late (12:30-1am) = 21.0%
• Moderately late (1:30-2am) = 11.7%
• Extremely late (2:30-7am) = 8.2%

Now, I KNOW how tempting it is to immediately compare your own sleep times to this chart and validate yourself for being normal or feel smug about being unique. But hold up. You don’t have the full story yet and I haven’t talked about a VERY IMPORTANT aspect about chronotypes. Yes, everyone has a genetic predisposition to when they naturally wake up, but your genetics are far from the only piece of the equation.

Chronotypes are not identities

Let me get back to why I hate these stupid bird labels of night owl, third bird, and morning lark (I’m mildly opinionated about it). And I swear to god if you bring up the bear, dolphin, and whatever other animals instead…

Okay, so here’s my beef with these animal labels. Last time I checked, I’d never heard of an owl turning into a lark as it aged. There’s something very static about an animal, and chronotypes are not static, they are a state of being. You should speak about chronotypes in a similar way you might speak about weight. You have some control over what your chronotype is, unless of course you have certain medical conditions that affect your sleep. I won’t get into that cause I’m not a doctor, I’m just some dude on the internet. Beyond the control you have over your chronotype, nature is also at work and shifts your chronotype as you age. 

Below is a chart displaying the average chronotype in the population by age. Notice that around the age when menopause might typically show up, the difference in average sleep times disappears. A study of transmasculine (taking testosterone) and transfeminine (taking estrogen and antiandrogens) people showed their chronotypes shifted towards later and earlier chronotypes respectively, clearly showing the role hormones play in your chronotype [2]. 

What’s important to recognize here is that if you learned about night owls in your 20s, you might naturally take that on as a part of your identity. “Oh I go to sleep late and feel most productive at night, I must be a nightowl!”. If it helps validate the fact that you wake up late in the morning and that your boss is mean mean man for making you wake up early, that’s great. But if you hold onto that identity as you age, then you might not notice that your habits around sleep are starting to hurt you.

You could get into your 30s and 40s constantly feeling tired and paradoxically finding it difficult to fall asleep despite your exhaustion. Your night owl identity refuses to consider that maybe your bedtime has shifted closer to 11pm than what it used to be at 1am. Remember that you have control over your chronotype based on your habits, but nature is also busy doing its thing. You can definitely have habits in direct opposition to nature.

What is social jetlag?

There are three very important clocks for humans. 

1. Our biological (circadian) clock: Essentially the chronotypes we just discussed. We’ll talk more in depth on the circadian clock later.
2. The solar clock: Which is the actual planetary time. This does not directly follow timezones as the solar time in Montreal (more west) would be slightly earlier from the solar time in Quebec City (more east) for example. In the extreme edges of timezones, this does make a difference in people’s felt experience.
3. Our social clocks: This is the time you see on your watch and that we collectively agreed as a society to set our appointments and schedules to. The social clock also refers to when you might start hearing your neighbourhood come to life in the morning and other social cues like that.

The more you can get those three clocks to be in agreement, the better you’ll sleep. 

When you have jetlag due to travelling, it’s because your circadian clock has been taken out of sync with the solar clock. It makes getting to sleep and waking up in line with the local social clock, very difficult. You may be familiar with this experience. However, you don’t need to travel to experience an out of sync circadian clock, you just need to make it out of sync with your social clock as opposed to the solar clock. When these two are out of sync, we call this “social jetlag”. So how does it happen? 

Let’s take a look at a concrete example. Timothy Youngman has to start work at 9:00am. To get to work on time and do his morning routine, Timothy wakes up at 7:30am with an alarm clock. Now little Timothy is 24 years old and his chronotype is quite late at the moment. Although his genetics pre-dispose him to be an early riser among his peers, his age and hormones still set his biological clock to fall asleep around 1am. With 8 hours of sleep time, this means his natural wake up time would be closer to 9:00am, not 7:30am. This hour and a half of space between when his alarm clock (social clock) wakes him up and when his biological clock would normally wake him up, is the amount of Timothy’s social jetlag.

Now Timothy can still get to bed at 11:30pm to try to get his full 8 hours of sleep, but he might find himself tossing and turning for a while. It means that every work day, he might be missing out on close to an hour of sleep. That’s a lot of sleep debt at the end of the week and he’ll likely make up for it by sleeping 9 or even 10 hours on the weekend. Throw in a party on Saturday night though, and it’s clear that Timothy is simply not getting enough sleep throughout the week because of his social jetlag. Do you know what happens when you consistently don’t get enough sleep? Quite often depression sets in and a bunch of other negative health effects [4].

Before you weep for our fictional character, I want you to know that there is still some hope to help him out of this dire situation.

The Circadian Clock

There’s something odd happening in cities. There’s a higher percentage of late chronotypes in the city than there is in the countryside [5][6]. Except, once you understand how your circadian clock works, it might not seem odd at all. 

Let’s start with the etymology of the word circadian. Circa- “close to”, dia- “day”, so it’s “close to one day”. More precisely it’s close to 24 hours or one rotation of the earth. Nature has created some phenomenal clock tech in our brains but it’s almost never exactly set to 24 hours in any given individual. What your brain thinks is a day might be 23.8 hours while my brain thinks it’s 24.3 hours for example. Because of these small timing errors, we also have some error correction tech to help us align our clock to the current solar clock. Honestly, this little error correction tool is badass because it lets us fly to another timezone and get used to their local time in a matter of days. 

How we think it works (please never assume neuroscientists are accurate), is we have our master clock tucked just behind our eyes and connected to the primary hormone center of the brain. When we see light, signals are sent to your master clock and it adjusts accordingly and your hormone schedule follows suit. The colors and light intensity of a sunrise versus those of a mid-afternoon sun are a part of those signals. A lot of different studies point to light being the most important and potent signal to your circadian clock. Our brains just don’t seem to care that much about the alarm clock sitting on your bedside table or when your shift starts at work. Light-dark cycles are key to your circadian clock.

So why are there more early chronotypes in the countryside? They spend more time outside than us city folk and an additional hour of time spent outdoors can correspond to a 30 minute earlier sleep time [7]. What’s also interesting is that the distribution of chronotypes gets tighter and tends toward earlier chronotypes the more people are getting sunlight. So are countryside people getting better sleep because of the sun? I mean, they also get to sleep to the sound of crickets. I’m definitely envious.
Black distribution is populations subject to strong signals (ex. the sun) to their circadian clocks. Hatched distribution is a population subject to weak signals (ex. indoor lighting) to their circadian clocks.

Okay, we made it! I left out a lot of details to try to keep things simpler but that was still a lot of theory. I hope you found it interesting but I’m more hoping it will give you some power over your sleep. Better understanding the tools I will now give you should make it easier to adjust them to your own life situation. Maybe we can save Timothy from his sleep deprivation along the way too.

Calculate your social jetlag (how much earlier your alarm clock wakes you up than natural)

The text in parentheses are for those who skipped the theory bits. Don’t be shy about not knowing the terms chronotype and social jetlag, it won’t affect your ability to follow the instructions below or get value from the advice that follows.

If you’re missing out on sleep and use the snooze button consistently, you already know you need to make adjustments. This tool will give you a sense of how bad things might be, but ultimately your felt-experience is where I suggest you put your focus, ‘cause that’s what matters right?

The following tool is an ultra condensed version of the Munich Chronotype Questionnaire developped by Till Roenneberg and his team in 2003 [7].

A positive social jetlag means you are likely missing that much sleep every single workday (or day that your alarm clock wakes you up). So a 30 minute social jetlag means you might be missing over 2.5 hours of sleep by the time you get to the weekend. But as Matthew Walker explains in his book Why We Sleep, you can’t quite make up 100% of lost sleep.

If you have a negative social jetlag, it could mean you are actually going to bed too early! This little tool is very bare bones and far from telling the whole story though. If you’re curious about the full questionnaire and going over your results together, feel free to reach out and become my client 😉

How to Reduce Social Jetlag

**important note: I’m not a doctor.  I spent four weeks studying this stuff, not years. This is not medical advice and serious sleep issues should be addressed with a licensed professional. Thanks for taking care of yourself properly.

Communication (without adjusting circadian clock)

With your boss: If it’s possible to start work later (i.e. not shift work) then talk to your boss about social jetlag and ask to start later in the morning. You’ll be a more productive and happier employee and they tend to like that. I’ve had clients in session that didn’t realize they could have these kinds of conversations with their superiors at work and just assumed the answer would be no. Make a proper case for yourself and try it out. If you ask to start later in the morning just “because I’m tired” then obviously your boss will likely respond with “go to bed earlier then…”.

With your partner: If you have social jetlag because you’re going to bed too late to match your partner’s bedtime, maybe talk to them about it. A well rested partner has a better capacity for emotional regulation, more energy to do their share of housework, and more energy for other activities in bed beyond sleep 😉. It might be worth having quiet hours in the house so everyone can sleep properly and benefit.

Respect the Light-Dark Cycle

A study published in the journal Sleep Medicine [8] aggressively got people to immediately start going to sleep and waking up 2 hours earlier than their regular sleep schedule. The result? Less depressive symptoms and participants that were more alert and less sleepy during the day. Here’s the protocol they used in the study and what I also recommend to my clients.

1. Go outside first thing in the morning. Send the right light signals to your brain that the day has started. Indoor lighting is just not the same, but super worst case at least sit by your brightest window in the morning.
2. Dim the lights at night. If it’s dark outside, it shouldn’t be too bright inside. This seems easy enough until you realize that your phone and your tv screen are actually the brightest things in your place. You look directly at the light source and it seriously sends mixed messages to your circadian clock. Give yourself at least an hour of proper dim lighting before you go to bed, aka no phones before bed. I know it’s hard, but it’s even harder being unhappy the next day (which only makes you crave your phone more).
3. Don’t eat right before bed. In the study they optimized for not eating 3 hours before bed time, but I know most schedules just don’t allow for that much. Do what works for your schedule, but if you are consistently eating less than an hour before bed, it may be time to seriously question your schedule.

Good Sleep Hygiene

• Bed time alarm: I really encourage my clients not to use alarm clocks to wake up and instead use them to go to bed at the right time (if it’s possible, obviously). This is in line with respecting the light-dark cycle. Have an actual alarm on your phone that tells you it’s time to start turning off screens and dimming the lights. You can also use software tools that will signal bedtime by tinting screen colours red or going grayscale, and blocking certain websites like your favorite streaming sites.
• Reduce Urgency at Night: Cortisol and melatonin are the two hormones connected to sleep. Cortisol is a stress hormone and general motivator that should be at its lowest at night and highest early in the morning. Want a great way to spike your cortisol just before bed? Check your e-mail to find out what new emergency you’ll have to deal with tomorrow. If you can’t fix something till the morning, don’t bother finding out what the problem is at night. It’ll only mess with your sleep and make you less capable of solving the problem in the morning.
• !!!Don’t keep your phone by your bed!!!: “I need an alarm clock and that’s on my phone!”. Buy an alarm clock separate from your phone and don’t use that excuse. I’m ready to fight you on this one because I care for both your mental and physical health. Sleeping with your phone charging beside you is incredibly common and incredibly awful for you in so many ways… Real self-care looks like keeping your phone out of your bedroom.

Want to nerd out even more? 

For the hardcore nerds, here’s the terminology you’ll need to read some of these research papers. I’ve also added an * to the papers that are a bit easier to read or that I find particularly relevant.

• Dim-light Melatonin Onset (DLMO): Melatonin is the hormone that makes you feel sleepy. The DLMO refers to when melatonin starts to ramp up in your brain during your circadian cycle.
• Midsleep on free days (MSF or MSF_sc): Because sleep duration isn’t consistent between people, scientists found it more relevant and consistent to use the middle time of sleep. They’ve also come to use the sleep patterns on non-work days as this tends to better correspond to people’s natural chronotype. The little sc you might come across is to say that they’ve done a correcting calculation using the participants’ social jetlag to get a better approximation of their chronotype.
• Phase Shift and Entrainment: When a stimulus changes your chronotype it is called entrainment as your circadian clock is being trained towards a new schedule. The amount and direction (earlier or later) it shifts your chronotype is referred to as the phase shift.
• Suprachiasmatic Nucleus (SCN): This little guy is your master clock. It’s a part of your brain that sits behind your eyes and is a part of your hypothalamus. Your optic nerves from your eyes cross just below it and this setup is part of the error correction technology I spoke about in the circadian clock section of the article.
• Zeitgeber: This is any stimulus that can affect your circadian rhythm.

References:

*[1] Roenneberg, T., Pilz, L. K., Zerbini, G., & Winnebeck, E. C. (2019). Chronotype and Social Jetlag: A (Self-) Critical Review. Biology, 8(3), 54. https://doi.org/10.3390/biology8030054

[2] Morssinkhof, M. W. L., Zwager, A., van der Tuuk, K., den Heijer, M., van der Werf, Y. D., Stenvers, D. J., & Broekman, B. F. P. (2024). Chronotype changes after sex hormone use: A prospective cohort study in transgender users of gender-affirming hormones. Chronobiology International, 41(5), 658–668. https://doi.org/10.1080/07420528.2024.2339989. 

[3] Roenneberg, T., Kuehnle, T., Juda, M., Kantermann, T., Allebrandt, K., Gordijn, M., & Merrow, M. (2007). Epidemiology of the human circadian clock. Sleep Medicine Reviews, 11(6), 429–438. https://doi.org/10.1016/j.smrv.2007.07.005

*[4] Wittmann M, Dinich J, Merrow M, Roenneberg T. (2006). Social jetlag: misalignment of biological and social time. Chronobiol Int. 23(1-2):497-509. https://doi.org/10.1080/07420520500545979. 

[5] Carvalho FG, Hidalgo MP, Levandovski R. (2014). Differences in circadian patterns between rural and urban populations: an epidemiological study in countryside. Chronobiol Int. 2014 Apr;31(3):442-9. https://doi.org/10.3109/07420528.2013.846350.

*[6] Borisenkov MF, Perminova EV, Kosova AL. (2010). Chronotype, sleep length, and school achievement of 11- to 23-year-old students in northern European Russia. Chronobiol Int. 2010 Jul;27(6):1259-70. https://doi.org/10.3109/07420528.2010.487624.

[7] Roenneberg T, Wirz-Justice A, Merrow M. (2003). Life between Clocks: Daily Temporal Patterns of Human Chronotypes. Journal of Biological Rhythms. 2003;18(1):80-90. doi:10.1177/0748730402239679

*[8] Elise R. Facer-Childs, Benita Middleton, Debra J. Skene, Andrew P. Bagshaw (2019). Resetting the late timing of ‘night owls’ has a positive impact on mental health and performance, Sleep Medicine, Volume 60, Pages 236-247, https://doi.org/10.1016/j.sleep.2019.05.001.