The more time a child spends in front of a screen, the harder it is to fall asleep. According to New Zealand researchers, this is all the more true in the 90 minutes before bedtime.
One last cartoon episode for the kids before going to bed? Better to let them do acrobatics on the sofa or read them a fairy tale… because screens make it harder for children to fall asleep.
A new study is driving the point home. New Zealand researchers looked at children’s activities during the 90 minutes before going to bed and the quality of their sleep (in Pediatrics) For this, they surveyed two thousand children and adolescents. Result: watching television is the main activity for 48% of young people at this time of the day, even before putting on their pajamas (41%) or brushing their teeth (41%). And over the 90 minutes before going to bed, on average a good half an hour is devoted to the screens of the television, computer or game consoles …
The researchers also found that those who spent more time in front of screens also took longer than others to fall asleep. A result that does not surprise Sylvie Royant-Parola, psychiatrist and head of a sleep exploration center at the Garches clinic. “Many studies have been carried out on the negative impact of television when it is watched too late at night,” explains the specialist and president of the Morphée network in Ile-de-France. With an exposure of at least 3 hours per day around the age of 14 or 16, there is a risk of developing sleep disorders in the years that follow ”.
As a result, sleep time decreases and so does academic performance. But the good news is, if the time spent watching television decreases to an hour or less, the risk of sleep disturbances is reduced. “Another survey, carried out on 2,546 boys and girls aged 13 to 16, shows that young people who have a television in their room go to bed later on weekends and on school days,” reports Dr Sylvie. Royant-Parola. The same effects are seen with video games or in front of a computer. This type of activity is not structured, without clearly defined beginning and end, they take a lot of time, promote a sedentary lifestyle, itself known to deconstruct sleep ”.
Listen to Prof. Patrick Lévy, sleep specialist at Grenoble University Hospital, “ these results must be taken into account by parents in the education of children “.
Beyond the observation, how can these disturbances due to screens be explained? In the study published in Pediatrics, the authors put forward three hypotheses. First, the phase shift. If children spend the time they are biologically programmed to fall asleep this poses a problem for sleep onset or quality of sleep.
The second explanation put forward by the authors is melatonin depression. Indeed, exposure to light from the screen just before sleep would affect the sleep / wake rhythm by suppressing the secretion of melatonin. “A Swiss research laboratory, which has been working on biological rhythms for more than 30 years, has done work on the subject,” recalls Sylvie Royant-Parola. Certain lights stimulate even more the level of awakening and the performances, the memorization ”.
For all of these functions, blue light is always more effective than green light or purple light. The temperature of the light is also involved. We distinguish between “hot” lights or “cold” lights. The latter, even for low light intensity, have a more marked blocking effect on melatonin, increase vigilance more and provide greater visual comfort than “hotter” lamps.
LED screens disrupt melatonin
“The Swiss research team compared the effects of a computer screen fitted with diode (LED) lighting, a technology increasingly proposed to illuminate screens, with those of a non-LED screen. . It turns out that these LED screens have a wavelength around 460nm, that is, in the blue spectrum. The subjects of the experiment, men aged 19 to 35, remained 60 cm from 24 ” screens for 5 hours in the evening. They had no activity on the computer but had to respond to vigilance and attention tests interspersed with periods of rest and relaxation (including a 20-minute relaxing video). Each subject repeated the same experiment but on the other screen a week later. For those who are subjected to LED screens, there is a clear suppression of melatonin, a decrease in the indicators of drowsiness and overall an increase in attention and performance in the tests performed.
The last hypothesis put forward by the authors of the study in the journal Pediatrics is more behavioral: falling asleep is disturbed because the child has been particularly stimulated by the cognitive tasks he has to do on the screen.
Listen to Prof. Patrick Levy, ” Sleep requires a transition, an airlock, which is not favored by screens. “
Whatever the explanation, for specialists, these results reinforce the need to inform about the risks for sleep, and health, of the use of screens at night (insomnia, depression, metabolic disorders). “Young people already have a biological propensity to delay their rhythm and, with these new interfaces, the phase shift risks being further increased,” explains Sylvie Royant-Parola. In particular, the population most at risk is that of adolescents who in the evening multiply leisure or work activities on computers ”.
.
