Your chronotype defines how much sleep you are able to get during the week and on weekends. I am, for example, a rather late chronotype. That means that any alarm clock in the morning would limit my sleep duration. And if I was (or you are) an early chronotype? Then any social activities in the evening would limit how much sleep I can get. As I would regardless wake up at my normal morning time. But let’s take a step back and start at the beginning.
What are chronotypes? Your chronotype is the expression of your sleep-wake cycle and of all other cyclical daily functions that happen in less apparent ways. Chronotypes are individual to each person—some people are earlier and some are later chronotypes—and follow a normal distribution, like nearly everything in nature.
How to find out your chronotype? Find out your chronotype by looking at your sleep pattern on your free days, when you are not driven by social commitments and when you don’t have to set an alarm clock. Note down when you fall asleep and when you wake up. Take the middle of these two times. This midsleep point is your chronotype.
Read on to get a full understanding of:
- What your chronotype is (and also what it is not)
- How you can find out your individual chronotype
- How your chronotype impacts your daily life
- Which factors impact your chronotype and which of these you can control
- How you judge your partner’s chronotype
- Why earlier chronotypes are praised in most cultures
- My personal experiences and your key takeaways
You will see that there are a lot of common misunderstandings about chronotypes in our cultures. And you will also get to know the full picture of why that is. The two key reasons are oversimplification and that we live in modern societies that still have a lot of folk wisdom and proverbs in their cultures.
What Are Chronotypes
What Are Chronotypes
To better understand what a chronotype is, let’s start with its meaning. Let’s start with where the name comes from. Chronotype is a combination of the Greek “chrónos,” which means “time”, and “type”. It is your “time type.” Which time you might ask? Great question: your internal time. Your chronotype is your “internal time” “type.” And the way your body expresses this.
In short, your body goes through a daily rhythm to optimize all your daily functions. This rhythm is based on your internal time and is called your circadian rhythm. Your “time type” or better your chronotype is the expression of this circadian rhythm.
Most notably, this means that your chronotype controls when you want to go to sleep and when you wake up thereafter. But your sleep-wake cycle is just one aspect. Even though it is the clearest expression.
Your chronotype also controls all the smaller changes that go along with your sleep-wake cycle. Through this process, different functions of your body have peaks and lows over different periods of time. For example, your hormone levels fluctuate during the day. Your genes are being activated at their specific times. Your body temperature changes cyclically. And also your physical and cognitive performances show regular daily fluctuations.
Sneak peek: If you are like the majority, then you need an alarm clock to wake up during the week. And you sleep longer during the weekend. Both because you are a rather late chronotype. But more about that later.
Let’s have a look at the most popular chronotype classifications next and then find out which one you are. (hint: you are probably neither of them)
Common Chronotype Simplifications
In many cultures and languages, chronotypes are named after birds. Like early birds and night owls. This suggests that your chronotype also falls in one of those two categories. So, are you an early bird? Or a night owl? Most likely, you are none of these two extremes. And your chronotype lies somewhere in the middle.
Let’s visualize this with another, more obvious, example: Imagine that you have to describe your body height as one of two categories. Are you a giant or a dwarf? Again, most likely, you are none of these two extremes. And your body height lies somewhere in the middle.
Your body generally doesn’t just fall into two categories. Body heights are continuous. And chronotypes are continuous too. It is just that their concept is a little more abstract and less obvious than your visible body height.
In 2016, Michael Breus popularized another classification of chronotypes. He grouped chronotypes into four categories. And he gave each of them an animal name.
If you were an early bird before then you are a lion now. If you were a night owl then you are a wolf. If your chronotype was anything in between then you are a bear. And if you don’t have a consistent chronotype (aka a regular sleep routine), then you are a dolphin.
For simplification and completeness purposes those four categories already work quite a bit better than the previous two. But let’s move on to give you the full picture.
Big Picture of Chronotypes
The Big Picture of Chronotypes
Ok, let me recap quickly. Your chronotype is the expression of your circadian rhythm. And your circadian rhythm is based on your internal time. Consequently, your chronotype is also the expression of your internal time.
Chronobiologists are those researchers who study your internal time and your chronotype. And what they are most interested in is your sleep pattern. This is because the other cyclical activities in your body largely follow your sleep. And because your sleep is relatively simple to observe.
Your sleep pattern also helps to find your chronotype. So let’s continue with your sleep pattern.
Firstly, your sleep has two main qualities:
- Sleep timing: when do you fall asleep and when do you wake up
- Sleep duration: for how long do you sleep
And those two major sleep qualities are independent of each other. That means that when you normally go to sleep does not automatically lead to how long you normally sleep.
So, to determine your chronotype, which of your sleep points would you use?
- When you fall asleep?
- When you wake up?
- Or even for how long you sleep?
The answer is neither of these. And all at the same time. Let me explain.
To determine your chronotype, chronobiologists use the concept of midsleep. And your midsleep is just as it sounds: the middle of your sleep.
Say, you go to bed at midnight, sleep for eight hours, and wake up at 8 am. Your midsleep point is simply the time in the middle. In this case, your midsleep point would be 4 am.
In their 2007 landmark paper, leading chronobiologist Till Roenneberg and colleagues studied the sleep patterns of more than 55,000 people.
On the left, you can see the distribution of chronotypes based on midsleep. And on the right, the distribution of average sleep duration.
Just like in nature
What does the data say about our early birds or lions? Only less than half a percent are early birds with a midsleep point between 1:30 am and 2:00 am. Assuming an average sleep duration of eight hours, that would mean that only less than half a percent fall asleep between 9:30 pm and 10:00 pm (four hours earlier than the midsleep point). And naturally wake up between 5:30 am and 6:00 am (four hours later). There are even earlier chronotypes, but their numbers are much smaller yet.
And what does the data say about our night owls or wolves? About four percent have such a late midsleep point between 7:00 am and 7:30 am. This means that they would fall asleep between 3:00 am and 3:30 am and wake up between 11:00 am and 11:30 am (again assuming a sleep duration of eight hours). Combined, even more people are later chronotypes. Even though their individual representation (the height of their respective bars) is smaller.
With those data points, it is much easier to see how the most common chronotype categories only reflect the extremes, right?
Which chronotype does the bulk of the population describe? Over sixty percent have a midsleep point between 3:30 am and 5:30 am. Meaning that they—and most likely you—fall asleep between 11:30 pm and 1:30 am and wake up between 7:30 am and 9:30 am (again with the assumption of eight hours of sleep).
And the majority of any half-hour-chronotype section? Slightly more than fourteen percent have a midsleep point between 4:30 am and 5:00 am. With the same eight-hour-sleep assumption as before this would mean that they fall asleep between 0:30 am and 1:00 am and wake up between 8:30 am and 9:00 am.
What about the average sleep duration?
- About sixty percent sleep between 7.5 and 8.5 hours (the three highest bars in the graph on the right).
- Nearly twenty-five percent sleep around 8 hours.
- More people sleep less than 8 hours than more than 8 hours.
- And a tiny part needs either less than 5 hours or more than 10 hours of sleep.
And as I mentioned beforehand, your chronotype (as identified by your midsleep point) is independent of your average sleep duration. Till Roenneberg summarized it best:
“There are just as many short and long sleepers among early chronotypes as there are among late chronotypes; or turned around, there are just as many early and late chronotypes among the short sleepers as there are among the long sleepers.Till Roenneberg
Thus, the notion that people who get up late sleep longer than others is simply wrong. This judgment presumes that all people go to bed at the same time, which we know isn’t true—certainly not in the world we live in today.”
What have we seen from this overview? Chronotypes vary a lot. And they follow a continuous normal distribution, just like nearly everything in nature. The bulk of chronotypes varies around the middle. And there are many more late chronotypes than early ones.
And one thing that I didn’t mention so far? The extreme ends of chronotypes are as far apart as twelve hours. Those people could theoretically share a bed without ever sleeping together.
With this general overview of chronotypes in mind, let’s get more specific. And have a look at what really matters. Let’s have a look at your specific chronotype.
Find out Your Chronotype
How to Find out Your Chronotype
We have seen that your sleep pattern is the most direct expression of your chronotype. So, to find your chronotype, we have to look at your sleep pattern. To be more precise, we have to take your sleep timing and duration into account and calculate your midsleep point.
But, there is one more thing that I didn’t mention yet. Your sleep patterns are most likely different during the week and on the weekend.
During the week you can’t follow your internal time. You can’t fall asleep and wake up as would be ideal for your body (unless you are an early chronotype; in this case: congrats!). You have to follow something that is called social time.
Social time is the time you live by based on your environment and social commitments. During the week, this is especially present in the form of your work or study schedule. And your alarm clock to wake up in time.
And what is the key sign that your social time interferes with your chronotype? Yes, that you have to set an alarm clock at all (just like 85 percent of the population
Now, let’s move on to find out your chronotype. To start, we only have a look at your “free days.” Those days when you and your body can make your own sleep decisions (most likely your weekends). This means that you were able to go to sleep when you wanted to and wake up without an alarm clock:
- For each night, write down when you fell asleep.
- For each following morning, write down when you woke up.
- For each of your nights (or even days if you are an extremely late chronotype), take the middle point between when you fell asleep and when you woke up. This is called your midsleep.
- When you have enough midsleep points, simply take their average.
Let’s see how that would work out for me as an example:
|Asleep at:||11:30 pm||12:30 pm||12:00 pm||12:00 pm|
|Awake at:||07:30 am||08:30 am||08:00 am||08:00 am|
|Midsleep:||03:30 am||04:30 am||04:00 am||04:00 am|
In my example, I am averaging eight hours of sleep, go to bed around midnight and wake up around 8 am. Over those three recorded nights, my midsleep ranges from 3:30 am to 4:30 am. And as we have seen above, this puts me where the majority is as well. Slightly on the earlier side, but not by much.
If you haven’t done so, go ahead now and calculate your midsleep point. Remember to only use the nights when your body was able to self-select your sleeping pattern. Got it? Great!
Now you can compare yourself to the general population again in below graph. The horizontal axis, numbered from 0 to 12, is where you can note your midsleep point. Is your chronotype rather early, just around average, or rather late?
But, also take this result with a grain of salt. You might have interfered with your internal time and weakened your circadian rhythm (e.g., through not enough light exposure during the day and too much at night or through eating too late). This might then have pushed your chronotype further than it would normally be.
For a complete overview, I recommend you the following post about “How Your Circadian Rhythm Works: All You Need to Know.”
Impacts on Your Daily Life
How Your Chronotype Impacts Your Daily Life
Do you remember how I mentioned before that your sleep timing and duration are independent of each other? Meaning that your chronotype doesn’t influence how long you sleep on average?
Well, this is only true for your average sleep duration. Meaning that it is the average of your sleep duration during the week—when your schedule makes you set an alarm clock—and on weekends—when you can wake up by yourself—combined.
If we only have a look at your sleep duration during the week, then your average sleep duration does depend on your chronotype. Why? Because your chronotype determines when you are able to fall asleep. And your alarm clock determines when you have to wake up. The later your chronotype, the less sleep you get. And the more sleep you’ll have to catch up during the weekend.
Here is how this looks for late chronotypes (midsleep later than 3 am):
|During the week||On the weekends|
|Go to sleep||The later your chronotype, the later you fall asleep||The later your chronotype, the later you fall asleep|
|Wake up||You need an alarm clock to wake up||The later your chronotype, the later you wake up|
|Result||The later your chronotype, the less sleep you get||You catch up on sleep|
The later your chronotype is, the later you fall asleep. Your working hours, on the other hand, are (on average) the same for everyone. Independent on chronotypes. This means that the later your chronotype is, the less you sleep during the week. And it also explains why 85 percent of the population needs an alarm clock to wake up: their chronotypes are simply too early for their working hours.
On the weekend, you then have the opportunity to catch up on sleep. The less sleep you get during the week the more your sleep debt is. And the more you sleep during the weekend. For some people, this even means sleeping through half of their free days to catch up on sleep.
This phenomenon is called social jet lag. Find out more in this post about “What Is Social Jet Lag and How to Overcome It.”
Here is how this looks for early chronotypes (midsleep earlier than 3 am):
|During the week||On the weekends|
|Go to sleep||The earlier your chronotype, the earlier you fall asleep||Social pressure makes you sleep later than your early chronotype|
|Wake up||You are ready and awake without an alarm clock||The earlier your chronotype, the earlier you wake up|
|Result||You get enough sleep||The earlier your chronotype, the less sleep you get|
If you are an early chronotype then the story is the other way round for you. You can fall asleep early enough during the week and get enough sleep. And you can wake up without an alarm clock.
But during the weekend, social commitments prevent you from falling asleep as early as you want to. Or better as early as your chronotype tells you to. But you then wake up you up as early as ever the next morning. And in this way, you don’t get enough sleep on your weekends.
As you have seen, your sleep duration during the week and on the weekend depends on your chronotype. And it is very different for early than for late chronotypes. This phenomenon is called “the scissors of sleep.”
Do you still remember your chronotype? The average midsleep point you calculated above? Great, cause in this graph you can see what that on average means for you.
Find your midsleep point on the horizontal axis and have a look at the corresponding vertical dots above. The interesting part is the difference between the white and black dots, indicating the sleep debt you build up. Either during the week if, your midsleep point is greater than three. Or during the weekend, if your midsleep point is smaller than three.
The data behind these “scissors of sleep” shows two key points on how your chronotype impacts your daily life:
- The later your chronotype (your midsleep point) the greater is the difference in your sleep duration during the week vs the weekend. And the more sleep debt you build up during the week.
- If you build up sleep debt during the week, then your wake up (aka work or school) times are too early. This is on average the case for everyone with a midsleep point later than 3 am. Which is about sixty percent of the population.
Why is this important for you? Because getting enough sleep has a significant impact on your daily performance. On and off the job.
In 2000, Williamson and Feyer compared the relative effects of sleep deprivation and alcohol on performance in a study with employees from the transport industry and the army. The result? Those participants that built up sleep debt had a reduced cognitive and motor performance. Even worse: when they had built up enough sleep debt, then their performance was worse than when they drank to the legal level of alcohol intoxication.
At this point you have two options: You can either align your social (aka work or study) commitments to your chronotype. Or you can try to influence your chronotype.
Let’s have a look at your second option now. For this, we need to see what influences your chronotype. And then find out which of these parts you can influence in your favor.
What Impacts Your Chronotype
What Impacts Your Chronotype
There are quite a few factors that influence your chronotype. Do you want to get a quick overview first? Sure, here you go:
- Your genes
- The season you were born
- Your age
- Your gender
- Your daily light exposure
- The current season
The ones that have the biggest impact are most notably your genes, your age, and your daily light exposure. And the one that you can influence and that will make the biggest difference for you? Hands down, that’s your daily light exposure! Let’s have a look at them next to get a big overview. One at a time.
Your Genes Impact Your Chronotype
Researchers found in twin studies that your genes explain a big part of your chronotype.
Also influenced by your genes is the way your body handles sleep pressure, which then influences your chronotype.
Late chronotypes have the ability to build up sleep debt during the week. And then sleep during the weekend to repay that sleep debt. This is how they handle having to wake up too early during the week. Remember the “scissors of sleep” example from above? This is the right part of its graph.
But early chronotypes don’t have that ability. They don’t just sleep longer when they go to bed too late. This is also why they often don’t get as much sleep on weekends as they get during the week. This is the left part of the “scissors of sleep” graph above.
The Season You Were Born
The Season You Were Born Impacts Your Chronotype
The light exposure during the first weeks after you were born also plays a role whether you are a rather late or early chronotype.
One possible explanation for this is that your body sets yourself up in those early weeks to receive as much light as possible. As an earlier chronotype, you also reach your circadian peak earlier. This helps you take advantage of the limited winter light. Whereas in spring and summer, it is advantageous for you to be a later chronotype, to reach your circadian peak later, and take advantage of all the light available.
Your Age Impacts Your Chronotype
Another big factor that influences your chronotype is your age.
Here is how your chronotype changes across your lifetime:
- You started as a very early chronotype as a child.
- And then you gradually became a later chronotype.
- During puberty and adolescence, you became a true late chronotype.
- But then, around the age of twenty (ok, around nineteen if you are a woman and around twenty-one if you are a man), you reached a turning point and started to become earlier again.
- This process of becoming an earlier and earlier chronotype will continue for the rest of your life.
Below graph visualizes this process:
One thing you can already spot here is the difference in chronotypes between men and women. So let’s look at this one next.
Your Gender Impacts Your Chronotype
As you can see in the graph above, there are gender differences for chronotypes. Even though they are quite subtle. Still, your chronotype is most of the time slightly different depending on whether you are a woman (in which case you would be slightly earlier) or a man (slightly later).
This chronotype difference starts around the end of puberty. One reason we have seen above is that teenage boys delay their chronotypes until about the age of twenty-one while teenage girls already reach their turning point at around nineteen years of age. Over time, this chronotype difference then becomes smaller and smaller. Before it largely vanishes at the age of around fifty, coinciding with the age of menopause.
Your Daily Light Exposure
Your Daily Light Exposure Impacts Your Chronotype
One of the biggest factors influencing your chronotype is your light exposure. The expression of your chronotype is strongly connected to your light environment. As is your circadian rhythm in general.
In short, we tend to get too little light exposure during the day. And too much during the evening and night. That means that during the day, your body does not get a strong enough light signal to set yourself up for a strong circadian rhythm. And during the evening and night, when your body doesn’t expect any light anymore, it gets too strong of a light signal to prepare you to sleep.
The consequence? You become a later chronotype. And your circadian rhythm becomes weaker, which means that your body cannot optimize your daily functions as it should.
Light is the biggest factor that influences your circadian rhythm – and hence your chronotype. But there’s more. Find out all about how you can strengthen your circadian rhythm and chronotype in this post: “How to Get Your Circadian Rhythm Back on Track“
The Current Season
The Current Season Impacts Your Chronotype
Because of your light exposure, your chronotype also depends on the season.
In summer, however, you tend to become an earlier chronotype again. Thanks to more natural light exposure. And less time spent indoors with relatively dim indoor light intensities.
If you want to read more about how light impacts your circadian rhythm and your chronotype, find out all you need to know in this post about “How Does Your Circadian Rhythm Work.”
Your Partner’s Chronotype
Your Partner’s Chronotype
If you live together with a partner, do you know which chronotype she or he is? Theoretically, it would be easy to find out through their sleep pattern, right?
Practically, however, it depends on whether you are a man or a woman. Why?
Because men tend to adapt to their partner’s chronotype. They adapt to the sleeping habits of their partner. They tend to go to bed at the same time as their partner. But when their partner is not home, men revert to their own sleeping patterns. Which in most cases means that they go to bed later.
Women on the other hand always tend to adapt to their partner’s chronotype. They rather go to sleep based on their own chronotype. No matter if their partner is around or not. So their reference point for their partner’s chronotype is their own chronotype
Now back to judging your partner’s chronotype: Can you already see where we are heading? Yes!
If you are a woman then you tend to think that your partner’s chronotype is similar to yours. And the later your own chronotype is the later you judge your partner’s chronotype to be. Simply because you might not have any other reference points.
And if you are a man then you tend to judge your partner’s chronotype more realistically. Because you know when you would go to bed when you are alone. And you know when you go to bed when you are with your partner. You have a more realistic reference point for when your partner goes to bed.
Chronotypes and Culture
Why Early Chronotypes Are Praised in Many Cultures
When you think about proverbs in your culture about sleeping, what comes to mind? Let’s have a look at a few together to see if there is any common wisdom:
- United States: “The early bird catches the worm.”
- Germany: “Morgenstund hat Gold im Mund.” (“The morning hour has gold in its mouth”)
- Spain: “A quien madruga Dios le ayuda.” (“God helps those who get up early”)
- Russia: “Кто пораньше встает, тот грибки себе берет; а сонливый да ленивый идут после за крапивой.” (“Who gets up early takes the mushroom for themself, and the sleepy and lazy one goes after the nettles.”)
- France: “À qui se lève matin, Dieu aide et prête la main.” (“Whoever gets up in the morning, God helps and lends a hand.”)
- Italy: “Chi dorme non piglia pesci.” (“Who sleeps doesn’t catch fish.”)
Yes, it seems like folk wisdom praises those people who get up early. And there was a time and place when that used to make sense.
Just imagine that you are part of a rural community. There is no electricity or anything else modern that would help you. Your productivity hours are limited by the sun. And so are those of everyone else in your community. And the success of you finding food not only depends on where you find it but also on when you find it.
In such a scenario, you would benefit from getting up and looking for food earlier. In fact, if you were the earliest chronotype then you would benefit the most. This was likely the case not just for your rural community but for most preindustrial societies. And it also gave us those proverbs from above and many more similar ones.
Earlier chronotypes had an advantage in rural and preindustrial societies. Back when it was important at what time of the day a task could be done. Or better when you could only catch the worm/ get gold in your mouth/ get help from god/ pick up the mushrooms/ or catch the fish in the morning. In our modern societies, however, this is not the case anymore.
We can now be productive whenever we want to be. Literally 24/7. Not restricted to daylight hours. But even though this temporal benefit of the morning hours has vanished, the proverbs haven’t. They are still common and dominant beliefs in our cultures.
But at least you and I now know where they come from. And we have also seen the chronotype data above to know that they might not be that applicable to us as they used to be for rural or preindustrial societies.
My Personal Experiences
I roughly know my chronotype. Or better my midsleep point. And more importantly, I know how it impacts my daily life. Let me explain.
Firstly, I have noticed how my age has impacted my chronotype. Over time, it has become easier and easier for me to get up early. And at the same time harder and harder to sleep longer. The last one doesn’t sound too bad until you want to sleep in after a long night out. But your internal body clock just wakes you up, just as nothing happened the night before.
The bigger impact on my daily life, however, is that it has become easier and more natural for me to wake up early. While I never seemed to get enough sleep during the week and hated my alarm clock, I do now mostly wake up just by myself. Without any alarm clock.
At the same time, I do feel the sleep pressure building up more in the evenings. That results in me going to bed much earlier than I used to. At least for the majority of all nights.
And there is one key component that has helped me to live in line with my chronotype: light exposure. Natural light exposure and light intensities have a massive impact on my chronotype. I can tell a big difference between days when I spent enough time outside vs those when I was inside for too much. And that difference is my sleep quality.
When I get plenty of natural light during the day, then I have a much easier time falling asleep in the evening. Like almost immediately falling asleep. And my overall sleep quality is so much better that I mostly sleep less and wake up fully refreshed and ready to start the day. It is that much of a difference.
There was a time where I first realized this, without knowing too much about my chronotype or circadian rhythm yet. This was when I was running daily before work. With no issues of waking up fully energized, sometimes as early as 5 am. These days, running into the sunrise felt like the most amazing thing ever. Until I got injured and couldn’t run anymore.
The difference was like day and night. Without my daily morning run, I had trouble waking up for work, which was about two hours later than when I was running beforehand. And I felt way less energized both in the morning and during the day.
Back then I blamed the difference in the change of my daily sports. But this was only partially true. The by far bigger part was my morning light exposure that prepared my body to start the day. And that prevented me from getting too little light over a regular day thanks to my office job.
Now with that knowledge, I either run or cycle or walk in the morning sun. Or rain. And ever since I made this a daily habit, my sleep quality is consistently great. And I wake up quite early yet fully energized to start the day.
(Disclaimer: I also cut down on artificial light exposure from the evening on. And eat my last meal in the afternoon. Both of which help to set me up for an earlier chronotype and a strong circadian rhythm. You can find out all you need to know in this article about “How to Get Your Circadian Rhythm Back on Track.”)
Finally, there are six key takeaways that I want to share with you:
- Your chronotype is the expression of your circadian rhythm. And both your chronotype and your average sleep duration follow a normal distribution. Not two or four categories. With cute animal names.
- You can find out your chronotype by calculating your midsleep point on free days.
- This is the middle between when you fall asleep and when you wake up at days when no social pressure has you go to bed late or wake up early with an alarm clock.
- When you have your midsleep point, go up again to “How to Find Your Chronotype” and compare yourself against the normal distribution.
- Your chronotype impacts your daily life. And especially how much sleep you can get during the week and on the weekend.
- If you are a late chronotype, then you most likely won’t get enough sleep during the week and catch up on the weekend.
- If you are an early chronotype, then you are fine during the week but most likely get less sleep on the weekend.
- Your chronotype depends on many different factors. The most powerful ones are your genes, your age, and your light exposure.
- Your daily light exposure is the one factor that you can control.
- And your daily light exposure has a great impact on your chronotype. It has the potential to strengthen your natural chronotype and to also set you up for a strong circadian rhythm. This comes with improved sleep quality and great health benefits.
- Your judgment of your partner’s chronotype depends on whether you are a man or a woman.
- As a woman, you tend to judge your partner’s chronotype just as late as your own.
- As a man, you tend to adapt to your partner’s chronotype and can hence judge it more realistically
- Your culture most likely still praises earlier chronotypes. While this did make sense for rural and preindustrial societies, it is an outdated belief in our modern societies.
And now back to you: If you reflect on your sleep patterns, are they different between your work/ school days and your free days? If so, what could you do to change that? If not, (congrats btw!) what has helped you to reach that point?
PS: If you found this information useful, spread the word and help those who would benefit most from it 🙂
- 1.Breus M. The Power of When: Discover Your Chronotype. Little, Brown Spark; 2016.
- 2.Roenneberg T, Kuehnle T, Juda M, et al. Epidemiology of the human circadian clock. Sleep Medicine Reviews. December 2007:429-438. doi:10.1016/j.smrv.2007.07.005
- 3.FRANK SA. The common patterns of nature. Journal of Evolutionary Biology. July 2009:1563-1585. doi:10.1111/j.1420-9101.2009.01775.x
- 4.Roenneberg T. Internal Time. Harvard University Press; 2012.
- 5.Williamson AM. Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occupational and Environmental Medicine. October 2000:649-655. doi:10.1136/oem.57.10.649
- 6.Hur Y-M, Jr TJB, Lykken DT. Genetic and environmental influence on morningness–eveningness fn2 fn2Part of the material reported here was presented at the 27th annual meeting of the Behavior Genetics Association. Personality and Individual Differences. November 1998:917-925. doi:10.1016/s0191-8869(98)00089-0
- 7.KOSKENVUO M, HUBLIN C, PARTINEN M, HEIKKILÄ K, KAPRIO J. Heritability of diurnal type: a nationwide study of 8753 adult twin pairs. J Sleep Res. June 2007:156-162. doi:10.1111/j.1365-2869.2007.00580.x
- 8.Natale V, Adan A. Season of birth modulates morningness-eveningness preference in humans. Neuroscience Letters. October 1999:139-141. doi:10.1016/s0304-3940(99)00672-2
- 9.Jankowski KS. Composite Scale of Morningness: Psychometric properties, validity with Munich ChronoType Questionnaire and age/sex differences in Poland. European Psychiatry. January 2015:166-171. doi:10.1016/j.eurpsy.2014.01.004
- 10.Randler C. Gender differences in morningness–eveningness assessed by self-report questionnaires: A meta-analysis. Personality and Individual Differences. November 2007:1667-1675. doi:10.1016/j.paid.2007.05.004
- 11.Roenneberg T, Kuehnle T, Pramstaller PP, et al. A marker for the end of adolescence. Current Biology. December 2004:R1038-R1039. doi:10.1016/j.cub.2004.11.039
- 12.Shawa N, Rae DE, Roden LC. Impact of seasons on an individual’s chronotype: current perspectives. NSS. October 2018:345-354. doi:10.2147/nss.s158596