Systematic review of sedentary behaviour and health indicators in school-aged children and youth

Abstract

Accumulating evidence suggests that, independent of physical activity levels, sedentary behaviours are associated with increased risk of cardio-metabolic disease, all-cause mortality, and a variety of physiological and psychological problems. Therefore, the purpose of this systematic review is to determine the relationship between sedentary behaviour and health indicators in school-aged children and youth aged 5-17 years. Online databases (MEDLINE, EMBASE and PsycINFO), personal libraries and government documents were searched for relevant studies examining time spent engaging in sedentary behaviours and six specific health indicators (body composition, fitness, metabolic syndrome and cardiovascular disease, self-esteem, pro-social behaviour and academic achievement). 232 studies including 983,840 participants met inclusion criteria and were included in the review. Television (TV) watching was the most common measure of sedentary behaviour and body composition was the most common outcome measure. Qualitative analysis of all studies revealed a dose-response relation between increased sedentary behaviour and unfavourable health outcomes. Watching TV for more than 2 hours per day was associated with unfavourable body composition, decreased fitness, lowered scores for self-esteem and pro-social behaviour and decreased academic achievement. Meta-analysis was completed for randomized controlled studies that aimed to reduce sedentary time and reported change in body mass index (BMI) as their primary outcome. In this regard, a meta-analysis revealed an overall significant effect of -0.81 (95% CI of -1.44 to -0.17, p = 0.01) indicating an overall decrease in mean BMI associated with the interventions. There is a large body of evidence from all study designs which suggests that decreasing any type of sedentary time is associated with lower health risk in youth aged 5-17 years. In particular, the evidence suggests that daily TV viewing in excess of 2 hours is associated with reduced physical and psychosocial health, and that lowering sedentary time leads to reductions in BMI.

Physical activity, sedentary time and adiposity during the first two decades of life

“…In large-scale cohort studies, self-reported time spent watching TV is usually used as a proxy marker of sedentary behaviour. Recent reviews (40)(41)(42) have concluded that TV-viewing is significantly associated with obesity and body fat, although one of these reported that this association was not likely to be clinically relevant (40) . However, few of the studies included in these reviews adjusted their analyses for objectively measured physical activity.…”

Simultaneous presence of excess weight and insufficient hours of sleep in adolescents: prevalence and related factors

“…A similar result was found in a study by Fotti et al 6 , in which adolescents who spent longer hours in front of the PC were less likely to have insufficient hours of sleep (> 8 hours). The relationship between excessive body time with excess body fat and insufficient hours of sleep/day is established in the literature 6,14,15 . However, when investigating PC time and the combination of conditions (excess body fat and hours of sleep), it can be observed that the cut-off point adopted for such classification in relation to excessive use of PC (≥ 2 hours) only identified alterations in relation to the number of hours of sleep and not in relation to body fat 6 .…”

“…Similar questions addressing the time of screen use were used in international studies 14 , with good reliability and reproducibility in Brazilian adolescents (CI = 0.76; 95% CI: 0.70-0.81; kappa = 0.52) 24 .…”

“…For the definition of TV, PC and total VG time, the sum of the number of hours during the week and the weekends was divided by the seven days of the week. These variables were later categorized into <two hours/day and ≥ two hours/day as recommended in the literature 14 .…”

“…There are several recommendations aimed at reducing body fat in overweight/obese adolescents, such as restriction of caloric intake, increased consumption of healthy foods, increased hours of sleep, greater engagement in physical activity and decrease in sedentary activities 1,12,14 .…”