Department of Social and Preventive Medicine, Université de Montréal, Montreal, Quebec, Canada.
Am J Epidemiol. 2010 Aug 1;172(3):255-62. doi: 10.1093/aje/kwq125. Epub 2010 Jul 8.
The effect of screen time during secondary school on percent body fat was examined in a cohort of 744 Canadian adolescents aged 12-13 years at baseline. Participants completed self-reported questionnaires on television viewing and computer use in 19 survey cycles over 57 months from 1999 to 2005. Triceps skinfold thickness and subscapular skinfold thickness were measured in survey cycles 1 and 19. Four screen-time trajectory groups identified in growth mixture modeling included steady-low screen time (73% of the sample), steady-high (10%), increasers (9%), and decreasers (8%). The effect of screen-time trajectory on percent body fat at survey cycle 19 was modeled in boys and girls separately by using linear regression, adjusting for baseline percent body fat and physical activity. Relative to that of steady-low screen-time trajectory group boys, percent body fat was 2.9 (95% confidence interval: 0.7, 5.0) and 2.4 (95% confidence interval: 0.5, 4.2) percentage units higher on average among "increasers" and "steady-high" trajectory group boys, respectively. There was no evidence that screen time has an effect on percent body fat in girls overall, although physical activity modified the association between screen time and percent body fat in both sexes. Efforts to prevent obesity in youth should emphasize reducing screen time.
本研究旨在探讨加拿大青少年中学阶段屏幕使用时间对体脂百分比的影响。该研究共纳入了 744 名年龄在 12-13 岁的青少年，通过问卷调查的方式收集了参与者在 1999 年至 2005 年 57 个月内 19 次调查周期中电视观看和电脑使用时间的数据。在第 1 次和第 19 次调查周期中，通过测量肱三头肌皮褶厚度和肩胛下皮褶厚度来评估体脂百分比。通过增长混合模型确定了 4 种屏幕时间轨迹组，包括稳定低屏幕时间组（占样本的 73%）、稳定高屏幕时间组（10%）、增加组（9%）和减少组（8%）。通过线性回归模型，调整基线体脂百分比和体力活动水平，分别对男孩和女孩的屏幕时间轨迹与第 19 次调查周期体脂百分比之间的关系进行建模。与稳定低屏幕时间轨迹组男孩相比，“增加”和“稳定高”轨迹组男孩的平均体脂百分比分别高出 2.9（95%置信区间：0.7，5.0）和 2.4（95%置信区间：0.5，4.2）个百分点。尽管体力活动在两性中均对屏幕时间与体脂百分比之间的关联有修饰作用，但总体而言，并无证据表明屏幕时间会影响女孩的体脂百分比。因此，预防青少年肥胖应强调减少屏幕时间。
