Reference: JAMA Pediatr. 2022 May 23 early online
As any exhausted parent will tell you, limiting screen time is somewhat of a fantasy these days given the omnipresence of opportunities to interact with media. While the American Academy of Pediatrics recommends less than two hours per day of screen time, the average American child gets more than seven. Add that to the exponential rise in childhood obesity rates, and it looks like we have a public health crisis on our hands. Previous studies have shown no effect of limiting screen time on physical activity (a surrogate for obesity prevention), but those studies all had low compliance. In an effort to study the efficacy rather than effectiveness of screen time limits, a group of investigators in Denmark designed an interesting study that essentially took compliance out of the equation.
The trial design was simple: they took families in Denmark with a) at least one child between the ages of six and ten who spent at least 2.4 hours per day on screens and b) a parent who worked or was in school full-time and randomized them to either two weeks without their phones or tablets (intervention group) or business as usual (control) and measured their physical activity and sleep. In this case, a total of 89 eligible families (181 children and 164 adults) were included after they filled out a survey of media habits which asked at the end if they’d be willing to “hand over their phone or tablet if allocated to the intervention group” in return for $75. Participants were almost 100% White. Median ages were 8-9 for children and 40-42 for adults. Children who participated in the study had a baseline screen time exposure of 5 hours per day.
The results were equally simple: there was a large effect size of the intervention among (specifically Danish) children, but not adults. Compliance with the intervention was 96% among families. Based on intention-to-treat analysis, there was a between-group difference of 45.8 minutes per day in children’s physical activity (95% CI, 27.9-63.6 minutes per day, in favor of the intervention; P < 0.001), but no differences in physical activity for adults. There were no significant differences in sleep for children or adults.
The bottom line here also seems pretty simple: if it’s not available, you can’t do it, and in this case, you have to do something else instead. The same principle goes for cigarettes, junk food, and soda. This is also why basically all diets and exercise programs have been shown to work while you do them. It’s the ‘doing them’ part that’ll getcha. This study does what it set out to do — it provides strong evidence that an actual reduction in screen time (not just advice to reduce it) is associated with increased physical activity in (Danish) children. Interestingly, adults seemed to replace screen time with other sedentary activities. Sidebar: when we first looked at the abstract and saw the 97% compliance rates in children, most of us were dumbfounded and were most driven to find out how these parents were able to enforce screen time limits. One of us (without kids, obviously) responded “why don’t parents just take the devices away?” After the rest of us got done laughing, we dove right into the full text only to discover that the participants had their devices physically removed from the home as part of the study protocol. They literally “handed them over”. For $75. Maybe it is true that parents can ‘just’ take the devices away… if they are paid. All in all, it turns out this study was less of a tutorial on how to limit screen time in real-life than it was a very good example of the difference between efficacy and effectiveness. Ultimately, we are material girls living in a material world, and we still need to figure out how to actually get people to willingly and sustainably give up some screen time and replace it with physical activity. But at least now we can be more certain that it will make a difference if we do.
For more information, see the topic Prevention of Obesity in Children and Adolescents in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Katharine DeGeorge, MD, MS, Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Dan Randall, MD, Deputy Editor at DynaMed; Carina Brown, MD, Assistant Professor at Cone Health Family Medicine Residency; Nicole Jensen, MD, Family Physician at WholeHealth Medical; Vincent Lemaitre, PhD, Senior Medical Writer at DynaMed; and Sarah Hill, MSc, Associate Editor at DynaMed.