“Don Quixote fulfilled nature by sleeping the first dream, without giving rise to the second; quite the opposite of Sancho, who never had a second, because he slept from night until morning, in which his good complexion and little care of him showed. Don Quixote's people kept him awake so that he woke up Sancho..."
This fragment of Don Quixote shows that in the 17th century sleep was biphasic, that is, it was divided into two phases separated by a period of wakefulness. The first part occurred between ten at night and one in the morning. This was then followed by a waking hiatus (known as a “watch”), lasting approximately three hours. The second stage was morning sleep, which lasted another four hours.
The waking phase was very useful: people dedicated it to ordinary tasks, such as adding fuel to the fire, taking medicine, or urinating. For peasants, waking up meant returning to work, whether it was watching the farm animals or doing household chores. It was also a time of prayer, philosophy, socializing and sex.
Biphasic sleep became marginal in the urbanized and illuminated core of northwestern Europe in the 18th century, becoming monophasic and with a delay in bedtime.
Thomas Alva Edison, considered the father of the electric light bulb (invented in 1879), believed that sleep “is a vestige of our caveman past.” Perhaps that is why it is not surprising that the discredit of night rest began with the discovery of electric light, which made it possible to illuminate the night. And teenagers were probably the most affected.
During adolescence, people live a time of independence and the emergence of new social roles. All of this causes changes in behavior, and sleep is no exception.
The main modification in sleep physiology at this stage of life is a delay in the time of the circadian clock, located in the hypothalamus and responsible for synchronizing rhythms such as sleep itself, body temperature, diet or physical activity. This leads to a delay in falling asleep.
To make matters worse, there is also more tolerance to the homeostatic pressure of sleep, that is, greater resistance to sleep deprivation.
As a consequence of all this, the time to go to sleep is increasingly later, while the time to wake up changes little, since it is determined by the start of classes. This circumstance causes the average sleep rate in adolescents to decrease drastically.
And it is not trivial, since a night's rest helps sculpt your brain. We know that during adolescence deep slow sleep (N3 phase of non-REM sleep) decreases, due to the reduction in the volume of the cerebral gray matter. On the other hand, the volume of the white matter increases, that is, the connections that are established inside the brain and outside of it.
There is also a correlation between IQ and the amplitude and density of the so-called sleep spindles, characteristic of slow superficial sleep (N2 phase of non-REM sleep) and which are expressed much more intensely in adolescence than in childhood. .
It is not surprising, then, that insufficient sleep impacts the mood of adolescents, increasing depressive symptoms, anxiety and emotional reactivity. In fact, sleep is disturbed in 95% of psychiatric disorders, such as depression, ADHD, impulse control disorder, anxiety, and bipolar disorder.
In addition, its deprivation has been seen to increase harmful behaviors among high school students: driving under the influence of alcohol, fighting, suicidal ideation or attempts, use of tobacco, alcohol and marijuana, and risky sexual behavior. And if that were not enough, it promotes obesity.
The digital age that we have lived in does not exactly contribute to solving the problem. Tablets, computers or mobile phones emit an enriched blue light that blocks the secretion of melatonin, a key hormone for inducing sleep and synchronizing circadian rhythms.
The American Academy of Pediatrics recommends that minors be exposed to this type of screen for less than two hours a day. It is clear that it is not fulfilled in almost any country in the world.
The harmful effects of these devices on adolescent sleep have been widely published. However, the phase delay characteristic of this age range, with later bedtimes and later morning awakenings, does not seem to depend on a greater sensitivity to light at night, but on the time delay of their clock. circadian.
It is a vicious circle: the shorter the sleep duration, the greater the exposure to screens the day after due to increasing fatigue, which leads to sedentary behavior. And on the other hand, it reduces the time of physical activity, which is beneficial for sleep.
In conclusion, sleep is essential in adolescents' brain maturation and plays a key role in supporting their mental well-being and cognitive functions. Public health interventions such as delaying the start of classes by an hour would improve attention in the classroom, cause fewer delays and, ultimately, reduce the rate of school failure.
This article was originally published on The Conversation. Juan José Ortega Albas is a somnologist at the Foundation for the Promotion of Health and Biomedical Research (Fisabio).
