Travis’ Note: Today we have a guest post from my colleague Allana Leblanc, reporting on a systematic that she recently published examining the relationship between sedentary behaviour and markers of physical, social, and psychological health. You can find more on Allana at the bottom of this post.
In March of this year (March 27th to be exact), the Canadian Society for Exercise Physiology (CSEP) released the first ever Canadian Sedentary Behaviour Guidelines for the Early Years (aged 0-4 years). These were released at the same time as the Canadian Physical Activity Guidelines for the Early Years (aged 0-4 years) and are the first ever, stand alone, evidence informed guidelines for this age group.
For information on the process and development of the guidelines, you can refer to an earlier post here. As well as to the published process papers in APNM (see here for the physical activity paper and here for the sedentary behaviour paper).
In brief, back in March 2011, CSEP, in partnership with the Healthy Active Living and Obesity research group (HALO) and ParticipACTION started work to concurrently develop Canadian Physical Activity Guidelines for the Early Years and Canadian Sedentary Behaviour Guidelines for the Early Years. Both of which would be informed by systematic reviews and following rigorous and transparent methods.
The systematic reviews that were used to inform the new guidelines were officially published a couple weeks ago and made available through APNM open access (for the physical activity review see here and for the sedentary behaviour review see here). Today I’m going to provide you with a brief overview of the sedentary behaviour paper.
What we did:
Study inclusion criteria
We searched 5 online databases for studies that looked at the relationship between sedentary behaviour and health in the early years (i.e. 0-4.99 years). The health indicators we included and their priority can be seen in Table 1.
Only high quality (i.e. RCTs, prospective cohorts, intervention studies) were included. You can see the number of included and excluded studies in the figure below. You can also check out the paper for the full search strategy [Travis' note: the actual figure is too wide for our blog, so just click the figure below to be taken to the full text of the article, which contains the original].
Data extraction and analysis
We used GRADE methodology (Grading of Recommendations Assessment, Development and Evaluation) to guide our review. Details on the development, process and framework for GRADE are heavily published and can be found elsewhere (Guyatt et al. 2011a; 2011b; 2011c; 2011d; 2011e; 2011f; 2011g).
In brief, GRADE is an internationally endorsed framework that provides a systematic and transparent methodology for clarifying research questions, determining outcomes of interest, summarizing relevant evidence and presenting recommendations based on the quality of available evidence. Once you’ve made up a search strategy and determined which articles meet your inclusion criteria, you assess the quality of available evidence. For this review, included studies were divided by age group and then by health indicator. Quality of evidence for each health indicator was assessed based on study design, risk of bias, consistency of results, directness of the intervention, precision of results, and possible dose-response gradient during data extraction. Randomized control trials begin at the highest quality evidence but may be downgraded as per assessment. Observational studies begin at the lowest quality evidence but can be upgraded if they score well (usually due to a dose response relationship).
What we found
In the end, we included a total of 21 studies (represented in 23 papers)
- 9 were in infants, 12 in toddlers, 10 in preschoolers (some overlapped age groups)
- 11 examined the relationship with adiposity
- 8 examined the relationship with cognitive development
- 6 examined the relationship with psychosocial health
- None examined the relationship with motor development or cardio-metabolic health indicators
- All studies used parent, caregiver or teacher report to quantify the time children spent watching television.
… in infants, there was moderate quality evidence to suggest television viewing elicited no benefits and may be harmful to cognitive development; and low quality evidence to suggest increased television viewing was associated with unfavourable adiposity. In toddlers, there was moderate evidence suggesting television viewing has a negative impact on adiposity, moderate evidence to suggest it negatively affected psychosocial health and low quality evidence to suggest it has a negative impact on cognitive development. In preschoolers, there was low to high quality evidence on television’s negative impact on adiposity, moderate quality evidence between increased television and decreased scores on measures of psychosocial health and low quality evidence on the inverse relationship between television viewing and cognitive development.
What we concluded
Current evidence supports the idea that increased television viewing is associated with unfavourable measures of adiposity, psychosocial health and cognitive development. Further, no evidence exists to suggest television viewing is beneficial for improved psychosocial or cognitive development. In several instance, a dose-response relationship existed between increased time spent watching television and decreased psychosocial or cognitive development.
Where we go from here
What was reported in this review is consistent with evidence in older children (i.e. aged 5-17 years) that increased screen time is associated with unfavourable body composition, decreased fitness, lowered scores for self-esteem and pro-social behaviour and decreased academic achievement (Tremblay et al. 2011). That being said, evidence included in this review did not provide specific information on the dose (i.e. frequencies, interruptions, times, or types) of sedentary behaviour associated with good health, nor did it provide definitive information as to how this relationship differs between boys and girls. Further, all studies included in this review reported on the relationship between television viewing and a health indicator (i.e. no other types of sedentary behaviour were explored). But as television viewing is only a crude measure of sedentary behaviour, it’s possible that results may in fact be underestimating its overall impact of television viewing on poor health.
Future work needs to focus on using direct measures (i.e. accelerometers, inclinometers) and standardized cut points within large cohorts of children. This would also help us understand specific times when sedentary behaviour interventions are most needed.
About the Author: Allana LeBlanc is a Certified Exercise Physiologist and Research coordinator. She is a co-author on the process papers outlining the new physical activity guidelines and systematic review, as well as lead author on the systematic review on which the sedentary behaviour guidelines are based.
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Leblanc AG, Spence JC, Carson V, Connor Gorber S, Dillman C, Janssen I, Kho ME, Stearns JA, Timmons BW, & Tremblay MS (2012). Systematic review of sedentary behaviour and health indicators in the early years (aged 0-4 years). Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme, 37 (4), 753-72 PMID: 22765839
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