Is Screen Time Keeping Kids Awake?

William T. Basco, Jr., MD, MS

May 20, 2013

Presleep Activities and Time of Sleep Onset in Children

Foley LS, Maddison R, Jiang Y, Marsh S, Olds T, Ridley K

Pediatrics. 2013;131:276-282

Why Are Kids Today Getting Less Sleep?

Children are getting less sleep. Their overall sleep time has been declining over recent decades. Studies have provided snapshots of how screen time, including television, computer, gaming, or handheld devices, is related to a later onset of sleep. In addition to being time fillers, electronic media may increase sleep latency by stimulating the brain compared with quieter activities such as reading, which may help the brain prepare for sleep. This study was unique in that it sought to reconstruct the entire 90 minutes of time before children in this sample fell asleep in order to obtain a more comprehensive view of how presleep activities correlated with time of sleep onset.

This study, conducted in New Zealand in 2008, used a complex, stratified, multistage sampling approach to select children 5-18 years old; 55% of the approached households participated. The children were mostly of European descent (71%), 19% were of Māori descent, 9.6% were of other Pacific Islander descent, and 13% were Asian. The data were collected in 2 formats for each child: first via an in-home, computer-assisted personal interview and subsequently by a telephone computer-assisted interview, conducted 1-2 weeks later. Each time, the children were asked to report on the 2 previous evenings' sleep time and presleep activities, providing data from 4 evenings for each child. One evening per child was randomly sampled to be included in these analyses. A standardized recall tool with more than 250 activities prompted the children to reconstruct their previous evening's activities in 5-minute increments (or more, as needed). Children reported the time that they fell asleep, and the analyses focused on the 90 minutes before the children fell asleep.

To simplify the analyses, the 20 most common activities were divided into 3 groups: sedentary screen time (television, computer, or video games), sedentary non-screen time (reading, eating, and talking), and self-care time. The analyses accounted for the child's age, sex, and whether the collected data represented a school evening or a weekend.

Study Findings

More than 2000 children were included in the study, 47% of whom were girls. The mean age of the children was 11.6 years. Participants were grouped into 4 bedtimes on the basis of residual analysis in regression. A very late bedtime group fell asleep at around 11 PM for the older adolescents (13-18 years old) and 10 PM for the younger children (5-12 years old). The very early bedtime groups fell asleep at 7:30-8:30 for younger children and 8:30 for adolescents. The most frequent presleep activities were television watching (48%) and self-care activities such as dressing or undressing (42%) and brushing teeth (42%). Compared with television watching, other electronic media were much less frequently used. Computer work was reported by 6%, computer or console gaming by 5%, and listening to music by 5%. Aggregated sedentary time involving screens comprised approximately one third of the 90 minutes of presleep activities.

Screen sedentary time varied from approximately 20 minutes among 5- to 12-year-olds who had very early bedtimes up to an average of 40 minutes among 13- to 18-year-olds. Older boys, with the exception of those with a very early sleep onset, had substantially higher sedentary screen time, approaching 45 minutes. Non-screen sedentary time accounted for 25 minutes in all children, and self-care accounted for 13-15 minutes among all children. Non-screen sedentary time and self-care time incrementally decreased with later sleep times, while sedentary screen time incrementally increased with each category of later sleep onset. Foley and colleagues concluded that sedentary screen time was inversely associated with time of sleep onset and that it accounted for the largest proportion of presleep activities.

Viewpoint

Several interesting findings here are worth emphasizing. First, the investigators admit that is very difficult to establish causality between the amount of screen time and sleep onset, but it is clear that screen time comprises a large portion of presleep activities for children. The limitation that sleep time was self-reported also makes it difficult to prove one of the more intriguing underlying hypotheses -- whether the type of activity is more or less conducive to sleep onset. It is also possible that screen time breakdown varies by country, so it is difficult to know how generalizable the findings are to US children. One of the interesting and perhaps counterintuitive findings for me was that most of the presleep screen time was television-related and not computer- or handheld device-related. Given that the data were collected in 2008-2009, I wonder whether the proportion of presleep time occupied by handheld device use might be even higher now. Regardless, remembering to ask about television in the bedroom when dealing with sleep issues remains paramount.