The circadian rhythm determines the physiological functioning of our body. But, far from being homogeneous, there are some interesting differences between people. Among them the existence of morning and evening people.
This refers to people who feel more active during the day or at night, respectively. It is not just a question of habits, but it has a genetic and physical background. What’s more, it also has a number of important consequences for our health.
Owls and Larks: Evening and Morning People
Yes, there is a difference between people who feel more active at night and those who do it during the day. So much so that there is a colloquial term to differentiate them: larks and owls. There is also a more technical one: morning and evening. While the former are more active in the morning, the latter do so when the day falls.
The morning people They tend to wake up easily in the morning and begin their activity with ease, quickly. As the day goes on, their performance drops. Under normal circumstances, they fall asleep easily at night, and they often feel tired from the lack of sun.
On the contrary, evening people It takes more effort to wake up fully, feeling lazy and clumsy in the morning. As the day progresses, they feel more clear-headed and mentally agile. When it comes to going to bed, at night, they remain active for longer and it may take time to fall asleep, although this is not decisive.
In general, these two habits obey two chronotypes. A chronotype is what a specific circadian cycle is called, adhering to a specific rhythm. Chronotypes determine many behavioral as well as physiological aspects (everything is related, after all). These are not static and depend on our own circadian cycle.
The internal clock that determines everything
All living things we have an internal clock that determines circadian functioning, that is, around 24 hours a day. This clock marks the daily rhythms, but also in the long term. This watch has an internal workings, to a certain extent independent, but it is adjusted every day by certain stimuli. Chief among them is sunlight.
In order to function, the circadian rhythm activates a cascade of activities that affect different organs in different ways. For example, the pancreas secretes more insulin during the hours of the day, which should be those in which we eat, and works more slowly at night, when we should not need to eat.
The main piece of the circadian rhythm is melatonin, a hormone in charge of controlling these metabolic cascades of which we spoke or, in other words, controlling how our body behaves. This also affects our attitude and our mood, of course.
What happens when our rhythm is out of square?
How is a chronotype acquired? In general, our circadian rhythm is adaptive. This means that we can mold it according to our needs. How? Forcing us to certain hours. It is not an easy task, as we will now see, but over time this biological rhythm adapts and moves. Thus, a morning person can become an evening person. Melatonin segregation will change your schedule and adjustments will be made for other types of stimuli.
The sun, which inhibits the secretion of this hormone, can cause an adaptation problem, but we have measures to avoid daylight in our homes. In short, we can adapt this rhythm almost without complications, beyond passing a period of adaptation. And what happens during that adaptation period? Or, in other words, what happens when a circadian rhythm is out of whack?
In the short term, people with a mismatched chronotype suffer from symptoms of tiredness and clumsiness, make impetuous and little thoughtful decisions. In its most acute stages there are mood swings and early depression may occur. Another more important question, as we can imagine, appears at the physiological level. Indeed, not following our circadian rhythm can affect metabolism in a number of ways.
Among other things, it affects various inflammatory diseases or metabolic problems of all kinds, including diabetes, fat accumulation, coronary heart disease or metabolic syndrome. In animals, we know that disrupting the circadian rhythm it ends up being lethal. For humans, the answers are no better. Of course, this brings us to the question we started with: not everyone has the same chronotype.
The difference between nocturnal and diurnal
Some studies, like this one carried out by the University of Granada, indicate that it is not okay to force people with a certain chronotype to work outside their “natural” schedule. As we said, this can affect your ability to make decisions, due to a lack of cognitive control that causes impulsivity, to take just one example. But if people can choose their time of activity by adapting your circadian rhythm, why would this be a problem?
Because in reality, it is not always possible to adapt easily. In the first place, like the whiting that wags its tail, there are personality differences between morning and evening people, and these promote a habit, as this study from the Complutense de Madrid shows. What came first the chicken or the egg? The answer is not that important because, in the end, what really matters is the behavior that people adopt.
On the other hand, there is also another question of a genetic nature. The CLOCK gene, of Circadian Locomotor Output Cycles Kaput, encodes a protein involved in the regulation of circadian rhythms and was identified by Joseph Takahashi’s group in 1997. Interestingly, a mutation associated with this gene was found in 2008 whose effect is manifested in the personality of the person, which is more docile and accommodating.
The CLOCK gene predisposes our chronotype to morning and evening. It does not mean that we cannot adapt to another rhythm, but that we have a certain tendency. This gene has also been linked to problems with cognitive development, obesity, and other metabolic issues. In conclusion, it is clear that our circadian rhythm is much more than a series of adjustable behaviors. There are a series of predefined patterns that make us tend towards one or another phase of the day. And, much more important, these characteristics are undoubtedly linked to our health.