Screen time disrupts internal body clock

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A new report from the Alliance of Girls' Schools Australasia reveals that for youths, spending time on screens affects their internal body clock and suppresses sleep and that they are far more susceptible to the effects of digital media than adults. Please read more below.

Researchers from the University of Colorado in the United States have reviewed nearly 70 international studies looking at the effect that screen time has on sleep in young people aged 5 to 17. The review, published in a special edition of Pediatrics focusing on screen time and youth health, found that 90% of studies reported an association between increased screen time and delayed bedtimes, fewer hours of sleep, and poorer sleep quality.

Monique LeBourgeois, Associate Professor of Integrative Physiology, says that digital media is increasingly pervasive throughout our society, including in the bedtime routines of children.

However, the use of electronic devices may have unintended effects:

Many parents believe that media, like watching a video or playing a game, actually calms their children before bedtime but, in fact, it may be the exact opposite and we may be creating the perfect storm to destruction of both the circadian clock and sleep.

The eyes of children, which are still developing, have larger pupils and more transparent lenses than teenagers and adults. This allows more light to hit the retina, affecting the cells which signal the internal biological clock. When light hits the retina in the evening hours, “it produces a cascade of signals to the circadian system to suppress the sleep-­promoting hormone melatonin, delaying sleepiness and pushing back the timing of the body clock”.

One of the studies examined by the University of Colorado academics found that the melatonin levels of school-­aged children fell twice as much as adults when exposed to the same amount and intensity of light. In particular, it is the short-­wavelength “blue light” -  emitted by all computers and smartphones currently available on the market - which suppresses melatonin. However, LeBourgeois says it is not just light that destroys sleep through “psychological stimulation”.

Whether it’s exposure to violent media, playing an exciting game or texting back and forth with friends, all of these interactions increase cognitive arousal, which in turn can decrease sleepiness.

Computer use is more destructive to sleep than watching television, possibly because computer-­based activities are more interactive than television watching. Nevertheless, 75% of studies found adverse links between television use and sleep (compared with 90% for overall screen time). Even just having technology in the bedroom can have a negative effect on sleep. A recent study of American children aged 6 to 17 found that leaving a device such as a mobile phone, computer or television switched on overnight in a child’s bedroom is “a significant predictor of insufficient age-­appropriate sleep duration”.

The 2014 Sleep in America Poll found that 75% of young people have screen-­based media in their bedrooms;; 60% use a device in the hour before bedtime;; and 45% use their mobile phone as an alarm. It was also found that 30% of pre-­school aged children and over 50% of school-­aged children and teenagers do not get as much sleep as they need, with older teens most likely to experience insufficient sleep. In fact, 58% of teens aged 15 to 17 slept seven hours or less per night, while only 10% slept the recommended nine hours or more.