Edit (14/07/11): Thanks to Gopinath for the article!
A common reason people give for the increased prevalence of childhood obesity is how youth spend more time in front of the TV/computer/video games now than they used to (a measure referred to as “screen time”). The average Canadian youth spends 6 hours in front of the TV/computer every weekday, and over 7 hours a day on the weekend (AHKC Report Card, 2011). So that begs the question – how can we reduce screen time?
Several interventions have been performed, and they have shown mixed results. But this could be due to a number of factors: the population they used, the methods they used or even chance. We can identify all the studies that have been done in this area using a systematic review, and then decide if they’re effective using a meta analysis. And that’s exactly what Wahi and colleagues did, in a study published in Arch Pediatr Adolesc Med this July.
More after the jump.
I’ll summarize their study here; a link to the paper follows this post.
What did they do?
They first identified 1120 trials that had any number of keywords present (combinations of the words: television, video games or computer, and one of : overweight, obesity or physical activity). 226 of these were duplicates. They then had two people manually review the abstracts, to determine which actually met their eligibility criteria. This excluded 804 articles. Following this, they reviewed the references of these studies. They then reviewed the entirety of the 90 remaining articles, and only 13 made it into the final study sample.
They read these 13 manuscripts in more detail, abstracting information about any changes in BMI, or reported changes in screen time. If the study didn’t report this, they contacted the authors to find out more information.
Finally, they evaluated the studies using Cochrane criteria, and used this to assess bias. They also used the Grading of Recommendations Assessments, Developments and Evaluation (GRADE) to assess the quality of evidence put forth by each study.
What did they find?
Six studies looked at BMI. They found no difference between the intervention and control arms.
Nine studies looked to see if screen time changed. They only found a significant reduction in screen time among preschool child younger than 6, but this was only from 2 studies (p = .04).
So what does this all mean?
Well, it’s not good. They found no difference between youth who got an intervention aimed at reducing screen time and those who didn’t on BMI or hours spent in front of computer/TV/playing video games.
However, this isn’t entirely surprising. BMI is a very tough outcome to change, especially in such a short time frame, and the median length of the studies was only 7 months in duration. Also, the age range was quite broad, going from 3.9 years to 11.7. This makes it quite difficult to see what works and what doesn’t. Finally, depending on how you measure screen time, different results might be seen. Some studies use self-report, while others used parental reports. This could lead to bias in the results.
And what now?
This study highlighted some important points. For one, the studies all look at different age groups, which makes comparing their results very difficult. This was highlighted by their finding that significant decreases in screen time only exist among younger youth.
They also touched on potential harm that might result from interventions. Only three of the studies they reviewed included a measure of harm (dissatisfaction with body shape, extreme dieting). Future studies should make sure they include this and don’t harm those they are trying to help.
Finally, while they didn’t find any consistent findings in their study, they do suggest that shorter, more intense interventions might be effective. However, that is a project for future researchers.
Link (may require registration): http://archpedi.ama-assn.org/cgi/content/short/archpediatrics.2011.122