Children's sleep not significantly affected by screen time

November 5, 2018

Science Daily/University of Oxford

As young people spend an increasing amount of time on electronic devices, the effects of these digital activities has become a prevalent concern among parents, caregivers, and policy-makers. Research indicating that between 50 percent to 90 percent of school-age children might not be getting enough sleep has prompted calls that technology use may be to blame. However, new research has shown that screen time has very little practical effect on children's sleep.

Screens are now a fixture of modern childhood. And as young people spend an increasing amount of time on electronic devices, the effects of these digital activities has become a prevalent concern among parents, caregivers, and policy-makers. Research indicating that between 50% to 90% of school-age children might not be getting enough sleep has prompted calls that technology use may be to blame. However, the new research findings from the Oxford Internet Institute at the University of Oxford, has shown that screen time has very little practical effect on children's sleep.

The study was conducted using data from the United States' 2016 National Survey of Children's Health. Parents from across the country completed self-report surveys on themselves, their children and household.

"The findings suggest that the relationship between sleep and screen use in children is extremely modest," says Professor Andrew Przybylski, author of the study published in the Journal of Pediatrics. "Every hour of screen time was related to 3 to 8 fewer minutes of sleep a night."

In practical terms, while the correlation between screen time and sleep in children exists, it might be too small to make a significant difference to a child's sleep. For example, when you compare the average nightly sleep of a tech-abstaining teenager (at 8 hours, 51 minutes) with a teenager who devotes 8 hours a day to screens (at 8 hours, 21 minutes), the difference is overall inconsequential. Other known factors, such as early starts to the school day, have a larger effect on childhood sleep.

"This suggests we need to look at other variables when it comes to children and their sleep," says Przybylski. Analysis in the study indicated that variables within the family and household were significantly associated with both screen use and sleep outcomes. "Focusing on bedtime routines and regular patterns of sleep, such as consistent wake-up times, are much more effective strategies for helping young people sleep than thinking screens themselves play a significant role."

The aim of this study was to provide parents and practitioners with a realistic foundation for looking at screen versus the impact of other interventions on sleep. "While a relationship between screens and sleep is there, we need to look at research from the lens of what is practically significant," says Przybylski. "Because the effects of screens are so modest, it is possible that many studies with smaller sample sizes could be false positives -- results that support an effect that in reality does not exist."

"The next step from here is research on the precise mechanisms that link digital screens to sleep. Though technologies and tools relating to so-called 'blue light' have been implicated in sleep problems, it is not clear whether play a significant causal role," says Przybylski. "Screens are here to stay, so transparent, reproducible, and robust research is needed to figure out how tech effects us and how we best intervene to limit its negative effects."

https://www.sciencedaily.com/releases/2018/11/181105132939.htm

Blue Light Could Help Teenagers Combat Stress

October 22, 2012

Science Daily/Rensselaer Polytechnic Institute (RPI)

A new study shows that exposure to morning short-wavelength “blue” light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

Adolescents can be chronically sleep deprived because of their inability to fall asleep early in combination with fixed wakeup times on school days. According to the CDC, almost 70 percent of school children get insufficient sleep -- less than 8 hours on school nights. This type of restricted sleep schedule has been linked with depression, behavior problems, poor performance at school, drug use, and automobile accidents.

A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that exposure to morning short-wavelength "blue" light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

Levels of cortisol, a hormone produced by the adrenal gland, follow a daily 24-hour rhythm. Cortisol concentrations are low throughout the day reaching a broad minimum in the evening before rising slowly again throughout the night. In addition to this gradual elevation of cortisol at night, cortisol levels rise sharply within the first 30 to 60 minutes after waking.

This is known as the cortisol awakening response (CAR). In nocturnal animals, the cortisol spike occurs at night, at the start of activity. It appears to be associated with the time of transition from rest to activity, upon waking. A high CAR has been associated with better preparedness for stressful and challenging activities.

"The present results are the first to show that low levels of short-wavelength light enhance CAR in adolescents who were restricted from sleep," said Figueiro. "Morning light exposure may help to wake up the body when it is time to be active, thus preparing individuals for any environmental stress they might experience."

Short-wavelength light has been shown to maximally suppress production of nocturnal melatonin and phase shift the timing of the biological clock. The effect of short-wavelength light on other biomarkers has not been widely studied.

The study included three overnight sessions, at least one week apart. All participants wore a Dimesimeter on a wrist band to measure light exposure and to verify the regularity of their activity/rest periods during the three-week study. The Dimesimeter is a small calibrated light meter device developed by the LRC that continuously records circadian light and activity levels.

During the study, adolescents aged 12 to 17 years went to sleep at 1:30 a.m. and woke up at 6:00 a.m., a 4.5-hour sleep opportunity. Each week, participants either experienced morning short-wavelength blue light (40 lux of 470-nanometer light) or remained in dim light.

http://www.sciencedaily.com/releases/2012/10/121022112847.htm