With the arrival of winter, many people have been (or are currently) victims of the flu (and other respiratory viruses). This condition, as a general rule, is associated with very annoying symptoms such as fever, mucus or cough that usually increase as night approaches. The question is why? There are several reasons that would explain this phenomenon.
To begin with, there is our biological clock, what is known as the circadian rhythm - which regulates sleep and wakefulness - and which affects, among other things, our immune system. “There are studies that affirm that the production of antibodies and other defenses (some immune defense cells) takes place more at night,” explains Antoni Trilla, head of preventive medicine at the Hospital Clínic and professor at the University of Barcelona.
“These same cells,” he continues, “which are usually mediators of inflammation, defend us, although at the same time they aggravate the symptoms a little by reacting. They work harder and there are more of them and that is probably why when they start reproducing at the beginning of the night this increase in symptoms appears.”
This circumstance affects both adults and children, and they do not have exactly the same circadian rhythm. “Indeed, the biological clock is different, but still, to a greater or lesser extent, there is a general pattern that is closely linked to the presence or absence of daylight,” Trilla argues.
There is still a second effect caused by the circadian rhythm and that has to do with the so-called cortisol cycle. “The release of endogenous cortisone, produced by our own body, is high during the day and low at night,” says Joan Seseras, family doctor. “This has an anti-inflammatory function and that is why inflammatory and feverish symptoms predominate at night,” he adds.
There are other reasons, also very plausible, that would explain the phenomenon. One of them has to do with the postural issue. When we go to sleep, the body is horizontal, which means that the nasal and throat mucus does not drain as easily, obstructing the upper airways. “It is a matter of gravity,” says Trilla. All of this means, she continues, that the respiratory symptoms get worse. "Solution? Put two pillows under your head to keep it higher and try to drink to stay hydrated.”
The same advice works for children. “The fact of lying down effectively causes the upper airways to become more obstructed,” argues Xavier Miró, pediatrician at the Disset de Setembre basic health area, in El Prat de Llobregat (Barcelona). He understands that the effect of secreting a little more mucus at night may also be due to this postural issue.
There is still another factor - although somewhat more strange - that can explain this greater nocturnal symptoms, according to Dr. Trilla. It is related to whether or not you are distracted. During the day, he reasons, one is normally busier and thinks less about the symptoms. Not so at night. “It is something very curious. Sometimes you have something in your joints that makes you walk a little lame. While you work, you are not very aware, but when you return home it hurts you again. The reality is that it has hurt you all day, but while you were busy you lost track,” he concludes.
