Objectives To examine the cross-sectional associations between screen time and cognitive development in preschoolers. Methods Participants were 97 preschoolers (36 to 60 months) in Alberta and Ontario, Canada in the supporting Healthy physical AcTive Childcare setting (HATCH) study. The time that children spent watching television, videos or DVDs (television time) or playing video or computer games (video game time) on a television, computer, or portable device was assessed using a parental questionnaire. Television time and video game time were summed to calculate total screen time. Adherence to the screen time recommendation (≤1 hour/day) of the Canadian 24-Hour Movement Guidelines was calculated. Expressive vocabulary and working memory were assessed using the Early Years Toolbox. Due to the distribution of working memory, it was categorized as a binary variable based on the median score. The associations between screen time and cognitive development were examined using mixed models (expressive vocabulary) or generalized mixed models (working memory). Results Screen time was not associated with expressive vocabulary. Preschoolers who had higher total screen time were less likely to have better working memory (OR=0.52; 95%CI:0.31, 0.88), despite the null associations for television time (P=0.155) and video game time (P=0.079). Preschoolers who met the screen time recommendation were more likely to have higher working memory capacity (OR=3.48; 95%CI:1.06, 11.47), compared to those who did not meet the recommendation. Conclusion Limiting total screen time to no more than one hour per day may facilitate working memory development in preschoolers. Screen time may be unrelated to expressive language development in this age group.

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学龄前儿童屏幕时间与认知发展之间的关联

目的 研究学龄前儿童屏幕时间与认知发展之间的横截面关联。方法 参与者是加拿大艾伯塔省和安大略省的 97 名学龄前儿童（36 至 60 个月），参与支持健康身体活动儿童保育环境 (HATCH) 研究。使用家长问卷评估儿童在电视、计算机或便携式设备上观看电视、视频或 DVD（电视时间）或玩视频或电脑游戏（视频游戏时间）的时间。电视时间和视频游戏时间相加计算总屏幕时间。计算遵守加拿大 24 小时运动指南的屏幕时间建议（≤1 小时/天）。使用 Early Years Toolbox 评估表达性词汇和工作记忆。由于工作记忆的分布，它被归类为基于中位数分数的二元变量。使用混合模型（表达词汇）或广义混合模型（工作记忆）检查屏幕时间和认知发展之间的关联。结果 屏幕时间与表达词汇无关。尽管看电视时间 (P=0.155) 和电子游戏时间 (P=0.079) 没有相关性，但总屏幕时间较长的学龄前儿童不太可能有更好的工作记忆 (OR=0.52; 95%CI:0.31, 0.88) . 与不符合建议的学龄前儿童相比，符合屏幕时间建议的学龄前儿童更有可能拥有更高的工作记忆容量（OR=3.48；95%CI：1.06, 11.47）。结论 将每天的总屏幕时间限制在不超过一小时可能有助于学龄前儿童的工作记忆发展。