CHRONOTYPE: Understand the variations in our circadian rhythms


Think that you are on vacation, with no appointments scheduled and are free to plan your routine thinking only of your well-being. What time would you sleep at night? And what time would you wake up in the morning?


There are no correct answers to these questions. There are people who will prefer to sleep and wake up early; while others will sleep and wake up very late. Each one of us has a profile and a preference for times to wake up, sleep and carry out our activities. These variations in our preferences are called CHRONOTYPES!


In this blog we'll understand what chronotypes are, why people's time preferences vary so much and what the consequences are.

What is the chronotype?


The duration of the day on our planet is 24 hours and we have to synchronize all our biological activities and functions to that. This is why our entire physiology follows a circadian rhythm (ie about a day). The main one of these rhythms is the sleep-wake cycle. It is because of this cycle, very well orchestrated by our brain, that we tend to sleep at night and stay awake during the day, for our entire lives.


However, not all people sleep and wake up at the same time, and sleep-wake cycles vary somewhat between people. That's where the chronotypes are established.


Chronotypes are our circadian preference profiles. In general, we have three different chronotypes:


· Morning: These are people who prefer to sleep and wake up earlier than the average population. Morning people are generally more energetic and work better in the morning. These people may find it difficult to work at night.


· Evening: These are people who prefer to sleep and wake up later than the average population. Evening people are generally more energetic and work best in the late afternoon or early evening and may find it difficult to work early in the morning.


· Intermediaries: These are people whose sleeping, waking and working times are closer to the population average. These people generally have more flexibility to adapt their routine to changes, whether for activities sooner or later than usual.


A classic survey carried out by researchers at USP in 1990 determined the frequency of each chronotype among Brazilians. It was noted that most people are of the intermediate chronotype (49%), while 39% are morning and 12% are afternoon. Mornings and afternoons can be further divided into moderates and extremes.


It must be understood that chronotypes are not diseases! These circadian preference profiles are completely normal patterns and are very important to our physiology. They are so normal that they are determined by our DNA. This subject is so relevant that in 2017 the Nobel Prize in Medicine was given to researchers who discovered the genetic basis of circadian rhythms. One of these genes (called PERIOD – or PER) seems to be one of the main determinants of our chronotype.


Knowing that chronotypes are determined by our DNA, we can conclude something important: Nobody chooses their chronotype. Being morning or evening is simply a manifestation of our normal physiological rhythms.


Is it possible to change your chronotype?


It is normal for the chronotype to change throughout life. For example, it is common for teenagers to be more afternoon, but throughout adult life we ​​tend to revert to a more intermediate pattern. This evening tendency during adolescence and early adulthood is completely normal and physiological. The causes are still not very well understood, but possibly it has to do with a delay in the effect of melatonin around the age of 15 to 25 years.

So, parents understand: although limits must be set, it's natural for your teenagers to want to go to bed a little later and take longer to wake up. They're just manifesting their normal circadian physiology!


When we get older, the tendency is to get more and more morning. That's why grandpa and grandma like to wake up so early. They are also manifesting their normal sleep pattern.


Sometimes we want or need to change our chronotype to suit the society around us. Social, work and play activities can even change our schedule preferences a little; but they don't necessarily change our chronotype. For example, an 18-year-old afternoon young man will have to get up very early to go to college. As much as he manages to wake up early, it doesn't alter the physiology and genetics that determine our circadian rhythms. As much as he manages to wake up early to go to college, he will continue to be afternoon.


Problems associated with chronotype


We have already mentioned that chronotypes are natural manifestations of our physiology and that they are not diseases. Still, they can be associated with very serious problems.


Problems do not occur because of the chronotype itself, but when our chronotype is not synchronized with our social or work activities. This is much more common than it sounds. Below are some examples:

· An afternoon teenager who needs to wake up very early to go to school.

· A morning grandmother who needs to stay up late to take care of her grandchildren.

· A morning person who works as a night watchman.

· An afternoon bus driver, who starts driving at 6 am.