Sleeping eight hours, going to bed at a reasonable time and still waking up feeling as though you have not rested. Or needing several days (or even weeks) to readjust to your routine after the holidays.

These situations are more common than they may seem and are often simply attributed to lack of sleep or accumulated tiredness. However, there is another factor that can significantly influence how we rest and how we adapt to schedules: the biological clock.

But what happens when this clock becomes out of sync?

What exactly is the biological clock?

Our body has an internal system that coordinates numerous physiological processes throughout the day. This “biological clock”, also known as the circadian rhythm, regulates important functions such as:

• When we feel sleepy.
• Periods of greater energy and concentration.
• The release of certain hormones.
• Body temperature.
• Rest and activity cycles.

To remain synchronised, this clock mainly uses natural light as a reference. However, factors such as sleep schedules, meals, physical activity or sudden changes in routine can also influence it.

That is why, after a holiday, travelling across time zones or a period of irregular schedules, the body may need time to readjust.

Not everyone has the same chronotype

You probably know someone who is full of energy first thing in the morning, while others feel they perform better towards the end of the day.

This does not mean that some people are more disciplined than others. To a large extent, it is related to their chronotype, that is, each person’s natural predisposition to be more active in the morning, afternoon or somewhere in between.

In general, three chronotypes can be distinguished:

• Morning type: people tend to wake up easily and achieve their highest performance during the first hours of the day.
• Intermediate type: they adapt more flexibly to usual schedules.
• Evening type: they tend to feel more active in the afternoon or evening and find it harder to get up early.

No chronotype is better than another. The problem arises when our biological clock and the demands of everyday life are not aligned.

For example, a person with an evening tendency who has to get up very early every morning may experience a constant feeling of sleepiness or lack of rest, even if they sleep a sufficient number of hours.

What is chronodisruption?

Chronodisruption is a state in which the biological clock is no longer correctly synchronised with the body’s natural rhythms or with the demands of everyday life.

In other words, it is as if our “internal clock” and our schedules were no longer keeping the same time.

This desynchronisation can affect different biological rhythms, such as the sleep-wake cycle or periods of activity and rest, making it more difficult for the body to function in a coordinated way.

Although it can occur for different reasons, it is more common in people who:

• Work rotating or night shifts.
• Travel frequently across time zones (jet lag).
• Regularly change their sleep schedules.
• Experience significant changes in their routines, such as after holidays or during certain periods of work.

When this situation persists over time, it can affect not only sleep quality. It has also been associated with a higher risk of developing certain diseases or with the worsening of existing conditions.

Therefore, identifying whether there is an alteration in the circadian rhythm can be an important step in understanding the origin of certain sleep-related problems and considering strategies aimed at resynchronising the biological clock.

What role does melatonin play in this process?

Melatonin is a hormone involved in regulating the circadian rhythm. Its production naturally varies throughout the day and helps the body identify when it is time to prepare for sleep.

However, beyond knowing an isolated value, it is much more useful to observe how melatonin changes throughout the day and determine whether this pattern is what would be expected according to each person’s chronotype.

For this reason, studying the melatonin curve makes it possible to assess the circadian rhythm and identify possible states of chronodisruption. To do this, melatonin concentration in saliva is analysed at different times of the day and compared with the person’s chronotype.

How can we find out whether the biological clock is synchronised?

Today, specific tests are available to objectively analyse how the biological clock functions.

The Melatonin Test from Laboratorio Echevarne measures melatonin concentration in saliva at different times of the day and compares it with the person’s chronotype. It also includes validated questionnaires assessing chronotype, sleep quality, daytime sleepiness and a sleep diary, providing a comprehensive overview of each person’s circadian rhythm.

This approach makes it possible to identify whether there is a mismatch between the biological clock and the chronotype, providing useful information to understand certain sleep disturbances and guide the most appropriate measures to promote circadian rhythm synchronisation.

When can it be useful to study the biological clock?

Understanding how our biological clock works can provide valuable information when there are persistent difficulties related to sleep or adapting to certain schedules.

This type of assessment can be particularly useful for people experiencing sleep rhythm disturbances related to schedule changes, shift work or jet lag. It can also provide information for people experiencing long-term stress, burnout syndrome, or those who want to better understand their biological rhythm in order to manage their health proactively.

Because sometimes the problem is not sleeping less, but sleeping at a time that does not coincide with the natural functioning of our body.

At Laboratorio Echevarne, the Sleep Study analyses the melatonin curve together with chronotype and other parameters related to rest to identify possible states of chronodisruption. This information should always be interpreted in the clinical context of each individual and together with an assessment by a healthcare professional.