Cardiovascular system (Lissak, G. 2018).

For more than three decades evidence has been accumulating regarding negative health outcomes of TV viewing as 'sitting' time. Along with technological advancement, this field of interest expanded to examine also a computer and video game time (Biddle, Bengoechea & Wiesner, 2017). Screen time sedentary behavior is claimed to increase the risk for obesity, HDL dysfunction, and high blood pressure which are major risk factors for cardiovascular morbidity (Merghani, Malhotra & Sharman, 2015; Goldfield et al., 2011; Martinez-Gomez, Tucker, Heelan, Welk & Eisenmann, 2009).



The relation between screen time and obesity can be explained by reduced sleep and physical inactivity and by exposure to advertising which negatively affects youth's dietary choices (Mihrshahi, Drayton, Bauman & Hardy, 2017; Biddle et al., 2017; Chahal et al., 2013). An increase in passive food consumption is another suggested factor for linking computer-related activities to obesity (Pérez-Farinós et al., 2017). Magee et al. (2014) argued that it is possible that obesity influences both sleep duration and screen time (TV viewing) because sedentary lifestyle may more common for obese children. Thus, the study suggested an interactional relationship between sleep and obesity.

A survey among children aged 9–10 associated three hours screen time or more to obesity (Nightingale et al., 2017). Among types of digital media, bedroom TV viewing was more associated with obese children and adolescents (Pérez-Farinós et al., 2017; Mihrshahi et al., 2017) and with forming a cardiometabolic risk (Staiano, Harrington, Broyles, Gupta & Katzmarzyk, 2013). A single video game session was associated with higher food consumption which was unrelated to hunger sensations. Moreover, in the study, after the video game playing time, food intake was not compensated for during the rest of the day. In normal conditions, an increase in plasma glucose follows a rise in satiety sensations, however, in the study, an increase in plasma glucose preceded food intake and reached a higher level than in resting conditions. Thus, results suggested the presence of acute stress (fight-or-flight response) associated with video game playing time. The stress response seemed related to a glucose release into the bloodstream (Chaput et al., 2011).


Blood pressure

Evidence exists in favor of tracking hypertension from childhood into adulthood (Gopinath, Hardy, Kifley, Baur & Mitchell, 2014). Sedentary behavior and its outcome physical inactivity have an inverse, and direct association with children's blood pressure in all age ranges, when associated with more than two daily hours of Internet use, watching TV and playing video games. Higher odds of elevated blood pressure were found when examining 2-9-year-old children with a two-year follow-up (de Moraes et al., 2014) or among 14-17-year-old adolescents (Cassidy-Bushrow, Johnson, Peters, Burmeister & Joseph, 2014). A marked rise in diastolic blood pressure was linked to each daily screen time hour among 6-year-old examined within a seven-year period (Gopinath et al.), and among pre-adolescents' (mean age 12.7 years). Interestingly every hour of non-screen reading was linked with a decrease in systolic and diastolic blood pressure (Gopinath et al., 2012).

Retinal arteriolar narrowing is considered a potential marker of future adverse cardiovascular events. A study which examined six-year-olds, associated each hour of TV viewing with increased arteriolar narrowing and a 10-mm Hg increase in children's systolic blood pressure. Findings indicated that high outdoor activity correlates with wider retinal arterioles than with children with low outdoor activity time (Gopinath et al., 2011).



Van Ekris et al. (2016) reviewed cross-sectional studies which measured overall sedentary behavior including screen time (TV viewing, computer use/video games). The authors found a moderate-to-strong evidence for an association of overall sedentary behavior and HDL-cholesterol level. Among obese adolescents (ages 14–18), video game playing was the only type of sedentary behavior associated with a reduction of HDL cholesterol (Goldfield et al., 2011). The same age range was examined by Martinez-Gomez, Rey-López et al. (2010) who concluded that screen time, over three hours, is associated with significant decrease in HDL cholesterol.

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