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COMMENTARY |
Departments of Pediatrics and Health Services, University of Washington, Seattle, Washington; Seattle Children's Hospital Research Institute, Seattle, Washington
Abbreviations: TV, television
When pediatricians think about environmental exposures during childhood, they might think of lead, pesticides, or dust mites. But truthfully, the greatest environmental exposure for most children is television (TV): they spend more time watching it than they do in any other wakeful activity, and it has significant effects on their health and well-being.1 Many of us routinely ask about lead, pesticide, or dust-mite exposure in selected patients, but we rarely ask about TV exposure.2,3 Perhaps this is because although we recognize the enormous presence that TV has in American childhood, we are not sure to which type of environmental exposure it is best likened. Is it like lead, a proven neurotoxin?4,5 Is it like alar, the presence of which on apples in the 1980s caused widespread panic but ultimately proved to be harmless?6 Or, is it like fluoride, which when added to our water supply has demonstratively improved the oral health of children?7 The reality is that TV can be likened to all 3, which has hampered a coherent national dialogue on the topic.8 For too long we have viewed TV monolithically and asked: "Is it good or bad?" Whether TV is good or bad for children depends a great deal on what they watch and how they watch it.8
The latest, and perhaps most controversial, way that TV has been likened to lead is its association with decreased attentional capacity. Claims that it shortens attention spans were initially based on anecdotal reports from teachers in the early 1970s who believed that the rise of TV viewing among preschool children led to 5-minute attention spans at school entry.9 Early empirical studies returned mixed results, but most were experiments that involved few children and, although well controlled, were underpowered to detect small but clinically significant effects.10–12 In 2004, we published a study using a large, nationally representative cohort and found an association between early TV viewing and subsequent attentional problems.13 Because of the observational nature of that study, those findings were not conclusive.
The study by Landhuis et al,14 published in this month's issue of Pediatrics, used a similar observational design in a mature and well-designed longitudinal cohort but had 2 important distinctions from our study. First, the children were older when the TV-exposure data were collected (school-aged children as opposed to infants). Although this may raise the possibility that the effects we found are true at all ages, given that school-aged viewing is highly correlated with preschool viewing, the mechanism of action may well be similar.15,16 Second, Landhuis et al adjusted for baseline attentional problems, which we were unable to do because it was not measured among the <3-year-old children we studied. Their findings lend further scientific credence to a possible causal association between exposure to TV and shortened attention span. At a time when the prevalence of attention-deficit/hyperactivity disorder in the United States may have risen 10-fold over a 20-year period, the report by Landhuis et al should rightly give us pause.17–19 No doubt critics will be quick to point out 2 limitations to this study that they would argue also make it inconclusive: (1) lack of data on content and (2) the observational nature of the design, which raises the possibility that some other latent confounder may explain the findings. I will address each of these concerns in turn.
First, Landhuis et al have no data on what programs the children were watching. There is increasing recognition on the part of media researchers that content is, indeed, a critical mediator in the effects of TV on children.20 In fact, it may be what makes TV capable of being like lead, fluoride, or alar. Consider that if the results of this study are to be believed, up to 1 hour of TV per day may have no effect on attentional capacity, and 1 to 2 hours of TV per day may actually lead to increased attentional capacity. These seemingly discordant findings can be explained if children who watch 1 to 2 hours of TV per day watch different shows or watch TV differently than those who watch >2 hours per day, a supposition that seems entirely plausible. Unfortunately, most existing data sets do not contain adequate data on what is being watched and how it is being watched, which undermines our ability to understand the contributions of these critical mediating variables to TV's effects on children.
Second, Landhuis et al used observational data. The authors did a commendable job of controlling for a host of potential confounders in a longitudinal framework. Although standard teaching tells us that only experiments can prove causality, causal arguments can be made on the basis of observational data.21 Although there have been no experiments in humans that link smoking to lung cancer, there are mountains of observational data coupled with biological plausibility of a connection, and it is now accepted as a scientific fact. Data in support of the association between TV and attention problems are mounting in observational data sets, and arguments for biological plausibility have been advanced.13,14,22
Nevertheless, these 2 limitations point us squarely in the direction that future research must move. More robust studies of the effects of TV on young children conducted in naturalistic settings are desperately needed. These studies must focus on content, and they must use experimental designs. The paucity of conclusive data about the effects of TV, particularly during early childhood, comes at a time when children are watching more and earlier than ever before.23,24 As a result, we are in the midst of an uncontrolled experiment on the next generation of children. Proceeding with caution that was lacking during the alar scare, our challenge is to find ways to ensure that TV is more like fluoride than lead in the future.
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FOOTNOTES |
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Address correspondence to Dimitri A. Christakis, MD, MPH, Child Health Institute, 6200 NE 74th St, Suite 210, Seattle, WA 98115-8160. E-mail: dachris{at}u.washington.edu
The author has indicated he has no financial relationships relevant to this article to disclose.
Opinions expressed in these commentaries are those of the authors and not necessarily those of the American Academy of Pediatrics or its Committees.
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This article has been cited by other articles:
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  Does Television Exposure in Childhood Lead to Adolescent Attention Problems? Journal Watch Pediatrics and Adolescent Medicine, November 21, 2007; 2007(1121): 4 - 4. [Full Text]
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