By Dr. Javier Rivera | Apr. 30, 2021 | Posts in English

Although it is something that any of us feel on a daily basis, we still do not know what fatigue consists of or what the mechanisms that produce it are.

Fatigue is synonymous with tiredness, and both words are used interchangeably to refer to an unpleasant feeling of lack of energy; but, in colloquial terms, we speak of tiredness when it originates as a consequence of physical activity and of fatigue when we perceive that the origin is more at the mental level.

In any case, almost always both sensations of physical and mental fatigue are closely linked and it is difficult to differentiate between the two components.

As a symptom, fatigue accompanies any disease, be it infectious, neurological, psychiatric, oncological, rheumatological, etc. The only condition is that it be chronic, or at least of a certain duration. On some occasions, fatigue is of such magnitude that it can be considered a disease in itself, as occurs in chronic fatigue syndrome.

It is frequently associated with other general symptoms such as pain, anxiety, depression, apathy, sleep disturbances or cognitive disturbances. All these symptoms have in common that they are produced in the central nervous system, so we can deduce that fatigue must also have the same origin.

If we analyze how physical tiredness behaves in a healthy person, it can be seen that as they carry out any activity, the level of tiredness grows progressively and that when they rest, especially sleeping, they recover the previous situation and the fatigue disappears.

Mental activity has a similar dynamic, but it is much more complex and has other components. Thus, activities such as thinking, studying, concentrating; emotions, such as those that accompany disappointments, problems, or joys as well; feelings of sadness, loneliness, anxiety, worry, etc., are some good examples of mental activity that lead to fatigue over time.

In mental fatigue, recovery is not as easy or as fast as in the case of physical tiredness. In the first place, mental activities do not cease as easily as physical activity. We can stop exercising abruptly, but we can’t stop feeling sad or worried about something as quickly. Secondly, mental fatigue is not recovered with rest, but rather by modifying feelings and emotions so that they do not continue to consume energy, and this takes time and is not so easy, so this type of mental fatigue is much longer lasting.

From this dynamic we can deduce that during physical or mental activity «something» is produced in our central nervous system -or «something» is spent- that is responsible for the appearance of the feeling of fatigue and tiredness.

The difficulty arises when we do not know what that «something» is and how to measure it. This also leads us to not knowing how to treat it so that it disappears and thus improves fatigue.

Meanwhile, we have to adjust to what we know and use those therapeutic measures that improve this situation.

Improving sleep quality is one of the most cost-effective measures. It is preferable to use sleep hygiene techniques instead of drugs, because the latter, especially benzodiazepines, produce several side effects and, in addition, lose effectiveness after a few weeks of use.

We also know that light aerobic physical exercise improves the quality of sleep and has no side effects.

Some antidepressants and anticonvulsants in clinical trials have shown a certain improvement in the symptom of fatigue, although the main objective pursued when using these drugs is the improvement of other symptoms, mainly those derived from emotions and feelings.

Lastly, some psychological therapies help to better face and manage emotions and feelings and for this reason they are also able to improve fatigue.