Health Risks, Correlates, and Interventions to Reduce Sedentary Behavior in Young People Jo Salmon, PhD, Mark S. Tremblay, PhD, Simon J. Marshall, PhD, Clare Hume, PhD Context: Opportunities for young people to be sedentary have increased during leisure time, study time, and transportation time. Purpose: This review paper focuses on sedentary behaviors among young people aged 2–18 years and includes evidence of the relationship between sedentary behavior and health risk indicators, an overview of public health recommendations, the prevalence of key sedentary behaviors, evidence of correlates of sedentary behavior and the effectiveness of interventions to reduce sedentary behaviors. Evidence acquisition: Although this is a narrative style review and not systematic, where possible, fındings from relevant review papers were summarized and a search of more recent literature was performed using computer-based databases such as PubMed, Google Scholar, ERIC, PsycINFO, Social Science Index, SportDiscus, and Health Reference Center – Academic. Evidence synthesis: Young people spend 2– 4 hours per day in screen-based behaviors and 5–10 hours per day sedentary. Ethnicity, sociodemographic status, having a TV set in the bedroom, and parental behavior appear to be the most consistent correlates of TV viewing time; however, few recent studies aiming to reduce TV viewing or sedentary time among young people have been successful. Conclusions: A growing body of evidence supports the development of public health recommen- dations to limit the time spent in screen-based behaviors. More research is needed to examine the prospective and experimental evidence of associations between overall sedentary time and health, determinants of sedentary behaviors other than screen-based behaviors, and interventions to reduce overall sedentary time or even alternative sedentary behaviors, such as transport- or education- related sitting time. (Am J Prev Med 2011;41(2):197–206) © 2011 American Journal of Preventive Medicine Context I n 1971, the average age at which children began to watch TV was 4 years; today, it is 5 months. 1 Elec- tronic entertainment products are now omnipresent and increasingly affordable. Trends in electronic enter- tainment products in Canadian homes are presented in Figure 1 and provide clear evidence of a “screen invasion” over the past 20 –30 years. 2 Other dramatic lifestyle changes include increased dependence on cars, 3 and a greater number of labor-saving devices in the home 4 and at work. These social and industrial changes have resulted in the permeation of sedentary behaviors into most as- pects of daily living of adults and children alike. Sedentary behaviors may be defıned as primarily sit- ting behaviors (such as TV viewing and computer use, or travelling in a car) that require low levels of energy expen- diture to perform (1.6 METs of rest). 5 Sedentary behav- iors are distinct and independent from physical activity behaviors of various intensities 1.6 METs (i.e., light-, moderate- and vigorous-intensity). Importantly, it is pos- sible to meet physical activity recommendations and still engage in high amounts of sedentary behavior. This pa- per focuses on sedentary behaviors among young people aged 2–18 years and describes evidence of the relation- ship between sedentary behavior and physical and social health and cognitive development, includes a summary of public health recommendations, provides the prevalence of key sedentary behaviors and overall sedentary time, reviews evidence of correlates of sedentary behavior from observational studies, and summarizes the effectiveness of interventions to reduce sedentary behaviors from early childhood to late adolescence. From the Centre for Physical Activity and Nutrition Research, Deakin University (Salmon, Hume), Melbourne, Australia; Children’s Hospital of Eastern Ontario Research Institute, University of Ottawa (Tremblay), Ot- tawa, Canada; and School of Exercise and Nutritional Sciences, San Diego State University (Marshall), San Diego, California Address correspondence to: Jo Salmon, PhD, School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood 3125, Australia. E-mail: jsalmon@deakin.edu.au. 0749-3797/$17.00 doi: 10.1016/j.amepre.2011.05.001 © 2011 American Journal of Preventive Medicine • Published by Elsevier Inc. Am J Prev Med 2011;41(2):197–206 197