Author Affiliations: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Canada (Dr Chaput; email@example.com); School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada (Dr Janssen); and Faculty of Physical Activity and Recreation, University of Alberta, Edmonton, Canada (Dr Spence).
To the Editor: Dr Ekelund and colleagues1 reported that time spent sedentary is unrelated to established cardiometabolic risk factors after adjusting for time spent in moderate- to vigorous-intensity physical activity (MVPA). Although the authors studied 20 871 children and adolescents and measured sedentary time in an objective way, we believe it is premature to conclude that sedentary time is not associated with adverse cardiometabolic health outcomes in children.
First, different types of sedentary behavior may have different metabolic effects and future studies should therefore investigate specific sedentary behaviors and not only the total accumulated time spent sedentary. For instance, sleeping 6 hours or less or more than 8 hours per night,2 TV viewing,3 and video game playing4 have been negatively associated with cardiometabolic health.
Second, though the cut point used to define sedentary behavior (<100 counts/min on an accelerometer) provides a useful estimate of sitting time, standing still time may also be included as sedentary time. This issue is an important one because breaks (interruptions) in sitting time can significantly improve cardiometabolic health.
Third, it is surprising that children with lower levels of sedentary time combined with lower levels of MVPA had the worst cardiometabolic outcomes. This group of children moves around a lot but at a low intensity.
Finally, food intake was not measured in this study and should be included in future research because of the strong link between poor dietary habits and cardiometabolic health and also because screen-time sedentary behavior has been shown to increase caloric intake in the absence of hunger.5
It will be important to better characterize the patterns and types of sedentary behavior in future studies with proper measurement of energy intake before drawing conclusions about sedentary time. In the meantime, the take-home message should be to increase children's participation in MVPA and reduce their screen-related sedentary time.
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Chaput J, Janssen I, Spence JC. Time Spent Sedentary and Active and Cardiometabolic Risk Factors in Children. JAMA. 2012;307(19):2024-2025. doi:10.1001/jama.2012.3629