A recent Norwegian study involving 10,000 young people aged 16 to 19 found that 90% use electronic devices an hour before bedtime. It showed that sleep duration was directly linked to the number and duration of electronic devices used. Other studies indicate that many young people in Europe and the US use up to five devices with screen during the day, including television, computer, iphone and smartphone, game console, etc.
The Scandinavian investigation points out that the cause of the decrease in the number of hours of sleep might lie in the fact that these young people do not go to bed earlier because the proper use of electronic devices. It also explains that the time of use of the devices is associated with greater difficulty in falling asleep.
According to this research, teenagers who spend more than four hours a day in front of a screen are 50% more likely to need over an hour to fall asleep at night. The same risks affect those who use electronic devices immediately before going to bed.
An American study reached similar conclusions and added new data. Students with smartphones at the bedside table were sleeping on average 20 minutes less on school days than students without these devices. Most of these also reported non-restorative sleep, which, according to the research, indicates that the use of smartphones not only makes it difficult to fall asleep but it also contributes to an interrupted sleep during the night. The origin of interrupted sleep may be that the device causes awakenings through messages, automatic sounds and light emission.