Parents of children and teenagers have long been warned about the dangers of screen time and digital devices before bed, the worry being that their sleep patterns could be harmed. But do screens really affect the length and quality of sleep?
Interestingly, while scientists say some of that anxiety is justified, research shows that using screens in bed is even worse for sleep than using screens for hours before going to bed, writes Rachael Taylor in The Conversation.
Taylor writes:
Sleep guidelines recommend no screen use in the hour or two before bed, but in our study, we found screen time in the two hours before bed had little impact on young people’s sleep. Instead, it was screen time once in bed that caused problems.
Using cameras to track device usage and sleep, we found using a device in bed could cause more harm than screen time right up to bedtime.
These findings challenge long-held assumptions about screen time at night and could help parents improve the quality of their children’s sleep.
Connecting sleep and screens
A number of global organisations recommend adolescents stop using devices in the hour or two before bed, and rather read a book or have quiet time with the family.
However, these recommendations are based on research with a number of limitations. The studies were designed in such a way that researchers could link sleep and screens.
But they don’t tell us if changes in how young people used screens had an affect on the length or quality of sleep.
Most of the existing research also used questionnaires to assess both screen time and sleep. Questionnaires are unlikely to capture true screen time accurately, particularly if you are interested in knowing more than just how long an adolescent has spent on their device.
To address some of these weaknesses in the previous research, we asked 85 adolescents aged between 11 and 14 to wear a body camera on their chest for the three hours before bed, for four nights.
These cameras faced outwards and accurately captured when, what and how adolescents used their screens. Because we were interested in overnight screen time as well, a second infrared camera was placed on a tripod in their bedrooms and captured their screen time while in bed.
The research participants also wore an actigraph – a watch-sized device that objectively measured screen time.
Teen night-time activity
It quickly became obvious the adolescents spent a lot of their screen time while in bed.
Our analysis looked at two time periods: from the two hours before they got into bed, and from once they were in bed (clearly under the covers) until they put their devices down and were clearly trying to go to sleep.
Our data showed 99% of the adolescents used screens in the two hours before bed, more than half once they were in bed, and a third even after first trying to go to sleep for the night. Just one teenager did not use screens before bed on any of the four nights.
The screen time before they got into bed had little impact on their sleep that night.
However, screen time once in bed did impair their sleep. It stopped them from going to sleep for about half an hour, and reduced the amount of sleep they got that night.
This was particularly true for more interactive screen activities like gaming and multi-tasking – when they use more than one device at the same time (like watching a movie on Netflix on a laptop while playing Xbox on a gaming device).
In fact, every additional 10 minutes of this type of screen time reduced the amount of sleep they got that night by almost the same amount – nine minutes.
Revisiting guidelines
Our research was an observational study looking at the established screen habits of young people.
The next step to better understanding this will be to conduct experiments that can actually prove different types and timings of screen time affect sleep.
That said, what we have already found challenges existing guidelines. Screens at night may not be the bogey man they have been made out to be. But allowing young people to have screens in bed can be detrimental to their quality of sleep.
So the simple message might be to keep those devices out of the bedroom.
Study details:
Screen Use at Bedtime and Sleep Duration and Quality Among Youths
Bradley Brosnan, Jillian Haszard, Kim Meredith-Jones et al.
Published in JAMA Paediatrics on 3 September 2024
Abstract
Importance
Although questionnaire-based cross-sectional research suggests that screen time before bed correlates with poor sleep, self-reported data seem unlikely to capture the complexity of modern screen use, requiring objective night-by-night measures to advance this field.
Objective
To examine whether evening screen time is associated with sleep duration and quality that night in youths.
Design, Setting, and Participants
This repeated-measures cohort study was performed from March to December 2021 in participant homes in Dunedin, New Zealand. Participants included healthy youths aged 11 to 14.9 years. Data were analysed from October to November 2023.
Exposure
Objectively measured screen time, captured using wearable or stationary video cameras from 2 hours before bedtime until the first time the youth attempted sleep (shut-eye time) over 4 non-consecutive nights. Video data were coded using a reliable protocol (κ = 0.92) to quantify device (8 options [eg, smartphone]) and activity (10 options [eg, social media]) type.
Main Outcomes and Measures
Sleep duration and quality were measured objectively via wrist-worn accelerometers. The association of screen use with sleep measures was analysed on a night-by-night basis using mixed-effects regression models including participant as a random effect and adjusted for weekends.
Results
Of the 79 participants (47 [59.5%] male; mean [SD] age, 12.9 [1.1] years), all but 1 had screen time before bed. Screen use in the 2 hours before bed had no association with most measures of sleep health that night (eg, mean difference in total sleep time, 0 minutes [95% CI, –3 to 20 minutes] for every 10 minutes more total screen time). All types of screen time were associated with delayed sleep onset but particularly interactive screen use (mean difference, 10 minutes; 95% CI, 4 to 16 minutes for every additional 10 minutes of interactive screen time). Every 10 minutes of additional screen time in bed was associated with shorter total sleep time (mean difference, –3 minutes; 95% CI, –6 to –1 minute). The mean difference in total sleep time was −9 minutes (95% CI, −16 to −2 minutes) for every 10 minutes of interactive screen use and −4 minutes (95% CI, −7 to 0 minutes) for passive screen use. In particular, gaming (mean difference, –17 minutes; 95% CI, –28 to –7 minutes for every 10 minutes of gaming) and multitasking (mean difference, −35 minutes; 95% CI, –67 to –4 minutes on nights with vs without multitasking) were associated with less total sleep time.
Conclusions and Relevance
In this repeated-measures cohort study, use of an objective method showed that screen time once in bed was associated with impairment of sleep, especially when screen time was interactive or involved multitasking. These findings suggest that current sleep hygiene recommendations to restrict all screen time before bed seem neither achievable nor appropriate.
Rachael Taylor, Professor, Department of Medicine, University of Otago
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