Sleep is essential for health: this is the theme of World Sleep Day 2023 which this year falls on March 17, or, as always, the Friday before the spring equinox. Just like eating well and exercising, sleep is a fundamental behavior for one’s physical, mental and social well-being (here we talk about the possible effects associated with Alzheimer’s disease). After 18 hours awake, it takes us a quarter of a second to half a second longer to react to a stimulus. And, after 24 hours, the brain’s ability to use glucose drops sharply, especially in areas responsible for reasoning and emotional control. Several studies have shown that getting behind the wheel after a sleepless night is like doing it drunk. While the lack of sleep has been indicated as a contributing cause of some accidents that have marked the last 50 years of history, including that of the Exxon Valdez tanker of 1989, the Space Shuttle disaster of 1986 and even that of Chernobyl, the same year .
Rem phase and non-Rem phase. Since the middle of the last century, the invention of instruments that record the activity of the brain and that of muscles and organs has made it possible to clarify what happens during the night. The electroencephalogram, in particular, has delved into the mystery of the sleeping brain, revealing a surprisingly varied and at times even more lively activity than that recorded in waking hours. The tracing shows two phases that alternate cyclically: the non-REM phase is the first to occur and occupies 75-80% of total sleep; the Rem phase, on the other hand, was already identified in 1953 by the American scientist Eugene Aserinsky, on the basis of the eye movements that are perceived behind the closed eyelids (Rem is the acronym of Rapid Eye Movements).
The non-Rem phase is in turn divided into 4 stages. The first represents the transition from wakefulness to sleep, lasts from one to seven minutes and can be easily interrupted by external disturbances, such as a noise. The second, lasting 10-25 minutes, constitutes 45-55% of total sleep and is characterized by a singular tracing of the electroencephalogram, with characteristic signs that scholars have linked to memory consolidation processes and learning. Stages 3 and 4, which precede the REM phase, constitute the so-called “slow wave sleep”, present only in the first part of the night, but crucial for the reorganization of brain circuits.
Physiologically, slow wave sleep is also characterized by a decrease in the production of stress hormones, such as cortisol.
Morning dreams. The importance of non-REM sleep has only emerged in recent years. Previously, in fact, scholars’ interest had mainly focused on the REM phase and the particularly lively brain activity that characterizes it: an irregular activity, concentrated above all in the areas related to sensations and movements (however, the muscles do not respond, because they are like paralysed). The REM phase is the realm of dreams that we remember the following day. Limited to short periods in the first part of the night, it lengthens over time and becomes predominant in the hours preceding awakening. Because of this, morning dreams are more complex and we remember them in greater detail.
Quantity and quality. Numerous studies have clarified that little and bad sleep makes us less efficient during the day and that, if the problem persists, it can damage health in many ways. However, estimating the amount of sleep needed by each of us is difficult, because there are individual variations but also because sometimes the problem lies not so much in the number of hours slept, but in the quality. For example, those who suffer from sleep apnea experience continuous awakenings (of which they are sometimes not even aware) which alter the architecture of sleep and create drowsiness and other difficulties during the day. However, “in the majority of the adult population, the 8-hour rule applies,” explains Francesco Fanfulla, head of the Sleep Medicine Center of the Maugeri Institute in Pavia. “However, this is an increasingly difficult goal to achieve.”
Sleep thieves. To get between us and the pillow there are well-established habits, such as that of using mobile phones, tablets and computers in the evening, whose screen emits a blue light that interferes with the production of melatonin (the hormone that induces us to sleep ). Good habits, adopted by individuals, can help chronic insomniacs, but they don’t solve the real problem, which is much wider and affects everyone. «Society evolves in a way that does not favor night rest; in the last century we have lost an average of one hour of sleep each», continues Fanfulla.
«For example, sports and recreational activities now take place mostly in the evening, the economist Jonathan White has come to speak of a “right to sleep” which should be guaranteed by law.
The sleep of the little boys. Nor is it better for the very young. According to an analysis by the University of Adelaide (Australia), which examined over three thousand researches carried out in 20 countries on more than 690,000 subjects, between 1905 and 2008 children aged between 5 and 18 lost 75 minutes of sleep per night, albeit with large variations depending on the geographical area. The consequences on the health of the youngest are particularly worrying, as demonstrated by research published at the end of July 2022 in the journal Lancet Child & Adolescent Medicine. The study followed 8,323 children aged between 9 and 10 for two years, divided into two groups: those who slept at least 9 hours per night (that is, the minimum amount recommended by the American Academy of Sleep Medicine for the age group between 6 and 12 years old) and those who slept less.
The results show that the latter tend to have cognitive (in information processing, memory and so on) and behavioral difficulties. The researchers were then able to link these problems to very specific structural abnormalities identified via MRI. “The anomalies observed among children who do not get enough sleep are typical of sleep deprivation even in adults,” comments Fanfulla. In particular, they concern the basal ganglia, a brain region involved in regulating the sleep-wake rhythm, and the cortex, responsible for more sophisticated cognitive functions.
To school later? «The study of Lancet it is much more than a wake-up call, because it confirms that lack of sleep in young people has cognitive and behavioral problems, and because it identifies a long-term effect on the structure of the brain», explains Fanfulla. “However, the solutions are not simple, also because hormonal factors add up to bad habits, which cause children to go to sleep later during adolescence”. It is a completely physiological fact, which was once mitigated by the lack of stimuli after a certain time, but which is now instead amplified by the presence of possible entertainment throughout the 24 hours.
To meet the physiological needs of the youngest, one answer seems to be to postpone entry to school.
Experiments in this sense, conducted abroad and also in Italy, demonstrate that the solution is feasible and that it works. For example, for some years now the Majorana Institute in Brindisi has chosen to delay the start of lessons and, at the end of 2020, a study conducted by the psychology department of the La Sapienza University of Rome evaluated the results of the decision . The research, published in the journal Nature and Science of Sleepfound that students who were able to get up an hour later in the morning had better academic results, higher attention spans, and fewer absences.
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