Tuesday, April 9th, 2013
A new study published in Pediatrics suggests that it may be, at least when it comes to risk for obesity.
WHAT DID THE STUDY DO?
91 teens (45 girls) around 14 years of age responded multiple times a day – via an electronic diary – to questions about what they were doing, over a 1-week period. Included were questions about a variety of screen time activities (for example, TV, video games, computer) and how much attention they were paying to each activity. Electronic diaries are an excellent method for getting kids to report on what they are doing in “real time” – it’s quick and easy for them to do and studies have shown that they provide reliable data using this method. The kids also had their height and weight measured by the research team in order to calculate their body mass index (BMI) – which is one metric used to measure risk for obesity.
WHAT DID THE STUDY FIND?
The overall findings were intriguing. First, the raw amount of screen time reported by the kids was not associated with their BMI. The statistical association of interest involved TV, but again it wasn’t about how much TV the kids were watching. Rather, it was how engaged the kids were when watching TV that was associated with BMI – the more a kid reported that they were paying the MOST attention to TV (versus all other activities), the higher their BMI.
WHAT DOES THE STUDY MEAN?
There are limitations to the study design that need to be addressed. The most prominent is that each teen was only observed during the 1-week period (this was a “cross-sectional” study). Finding statistical associations in a cross-sectional design limits what we conclude because we can’t tease apart what leads to what. It could be that kids with the highest BMI levels were the most likely to become engaged in TV viewing. It could be that TV viewing was one of the causative factors for their increased BMI levels. The point is that with these kinds of data we can’t distinguish between those interpretations. And of course we don’t have data on younger kids from this study, so technically there are no inferences to be made on non-teens.
WHAT SPECULATIONS CAME OUT OF THE STUDY?
Noting the limitation discussed above, researchers use cross-sectional data to generate and support hypotheses to be tested in future studies. The interesting idea that comes out of this paper is the speculation on the specific health risks associated with TV viewing versus other forms of screen time. One deserves particular mention. They note the potential impact of commercials promoting unhealthy foods – which may be particularly influential for kids who are highly engaged watchers. What’s interesting here is the idea that it’s not just about screen time, and it’s not just about TV – it’s about the specific risk of being a highly engaged TV viewer that seems to be linked with BMI. But future work will need to measure all these things and evaluate them longitudinally.
WHAT’S THE TAKE-HOME MESSAGE HERE?
Clearly this paper is the beginning, and not the end, of the story. The story, however, may be quite informative for parents if future studies replicate and expand the finding – and particularly if longitudinal studies provide clearer evidence of the directionality of the findings and support for the hypothesized mechanisms. Starting with younger samples of kids and tracking them across time will help determine if engaged TV viewing is especially linked with increases in BMI. But right now the interesting idea for parents to think about – at all ages – the potential downside of when kids get too attached to passive activities. This study suggests that TV may be the worst culprit for multiple reasons. But the bigger picture is that we are probably moving away from talking about screen time per se – many kids are increasing rather than decreasing screen time – and shifting toward a focus on unhealthy habits and unhealthy content that may be linked with specific types of screen time.
So … right now keep on eye on when your kid seems most likely to pair eating with screen time, and see if you can discourage that link. And see for yourself at home if it seems to happen more when they are especially glued to the tube.