In 2014, the National Sleep Foundation found that most 15- to 17-year-olds routinely get seven hours or fewer hours of sleep, which is a good two hours less sleep than they need for a healthy life. The foundation also found that sleep quality was better among children who turned their digital devices off before bedtime than those who took their devices to bed. It would thus seem that there is a connection between screen time and sleep. Is this connection somatic (purely physical), psychosomatic (caused by the mind) or just mass hysteria brought about by digital ubiquity?
At a very basic level, time on a gadget during bedtime is time not spent in sleep; 6- to 10-year-old children with three technology types in their bedroom achieved 45 minutes less sleep than those without. It is only logical to believe that older children, with their more active social life, would spend more time on gadgets than the surveyed pre-tweens. Delayed bedtime or truncated total sleep time caused by "time displacement" by technology and media items in an adolescent's bedroom has been reported to result in sleep deprivation, sleep-onset latency (SOL), sleep difficulties, night-time awakenings, and parasomnias.
Time displacement is augmented by biochemical effects of screen time as well. Adolescence is already associated with circadian (sleep) phase alterations, which along with social demands (early school timings etc.), can cause sleep deprivation. It is well-known that light also affects the circadian rhythm. Light suppresses melatonin, the sleep-promoting hormone, and recent studies have found that backlight from gadgets (particularly tablets set to full brightness) can cause statistically significant melatonin suppression after just two hours of exposure. The dose, exposure duration, timing and wavelength of light play important roles in sleep patterns. Suppression of melatonin secretion and alterations of sleep rhythms are more sensitive to short-wavelength light (blue) than mid- (green) or long-wavelength (red) light especially at at the brightness at which gadgets typically work.
Longer screen time is also linked to eating disorders and higher calorie intake. Longer media hours have been found to be associated with consumption of more soft drinks and junk food. There is also strong evidence for a direct connection between screen-based sedentary behavior and weight, particularly when screen time exceeds two hours. How is this related to sleep? A 20-year review of obesity-associated diseases among children aged 6 to 17 conducted by the Centers for Disease Control and Prevention concluded that obesity in children is a reason for increased incidence of sleep apnea that leads to sleep deprivation. Sleep deprivation in turn leads to more obesity in a vicious cycle that can effectively be traced back to extensive media use.
The psychological and physiological unrest caused by media and social interaction may also interfere with the ability to fall and stay asleep. Technostress and ICT or information and communication technology stress, the state of mental and physiological arousal observed in persons who are heavily dependent on computers, gadgets and e-games, are now pervasive maladies. Studies have shown that the stress due to excessive technology use is related to sleep disturbances. Researchers at the University of Gothenburg studied the habits of more than 4,100 Swedish men and women, aged between 20 and 24, and found that those who constantly use a computer or their mobile phone can develop stress, sleeping disorders and depression. Sleeping disorders and depression are connected by a common chemical -- melatonin and we already know that blue light of the screen can disrupt melatonin in the body, leading not only to sleep deprivation, but also depression. Like obesity and sleep deficit, depression and sleep problems form a vicious cycle, one feeding the other in a downward spiral.
No correlation study can be complete without awareness of possible pitfalls of association. For example, the observed connection between sleep deprivation and technology use may not point to a causal impact of screen time on sleep outcomes. There is a high possibility that the reverse is true because youth who need less sleep or have sleeping disorders may spend more time with technology, either as a coping mechanism or just to pass time. Another possible source of error in such correlation studies is that they are largely based on self-reported or parental reported data of screen exposure and the outcome variables. Such reports could be highly opinionated and are often not validated against an objective standard. Teenagers, for example, can overestimate or underestimate their total sleep time/problems vis-a-vis screen time due to ignorance, peer pressure and even denial. Measurement errors and inconsistencies could also lead to faulty associations.
Like breathing, eating and drinking, sleeping is a life-sustaining activity, and anything that adversely affects it must be dealt with before damage becomes irreversible. However, it is regressive to believe that technology itself must be ousted because of sleep problems, much like advocating that breathing is dangerous because of air pollution. Logical moderation is the key to living. There is clearly a dose-response relationship between screen time and sleep and a threshold for screen-based recreation. For example, the risk of sleep problems was found to increase two-fold in adolescent girls engaging in screen-based activities for four or more hours per day. So, is four hours the magic number? Can the limit be generalized for an entire population? Obviously not. The threshold must eventually be set by every individual based on their own nature and needs.