The association between screen time (ST), including that for smartphones, and overweight/obesity in children was examined separately for boys and girls, considering the influence of lifestyle factors. A cross-sectional study was conducted in 2,242 Japanese children (1,278 girls) aged 10–14 years. Overweight/obesity was defined by the International Obesity Task Force. Logistic regression analysis showed that only for girls, total ST (≥4 h), smartphone ST (≥3 h), and non-smartphone ST (≥2 h) were all independently and significantly associated with overweight/obesity compared to <2 h total ST, non-use of smartphones, and <1 h non-smartphone ST. Thus, smartphone ST ≥3 h and non-smartphone ST ≥2 h were additively associated with overweight/obesity in girls only. Girls having smartphone ST ≥3 h and non-smartphone ST ≥2 h were 6.79 times (95% CI: 3.11–14.81) more likely to have overweight/obesity than girls with less usage of both. In girls, when total ST was ≥4 < 5 h or smartphone ST was ≥2 h, the significant association with overweight/obesity disappeared when physical activity was ≥60 min/day and sleep time was ≥8.5 h. In addition, none of these associations was significant in boys. In Japanese girls, smartphone ST, non-smartphone ST, and total ST were all significantly associated with overweight/obesity. To avoid overweight/obesity, it is suggested to keep smartphone ST, non-smartphone ST, and total ST to <3 h, <2 h, and <4 h, respectively, and to engage in sufficient physical activity and sleep time.

考虑到生活方式因素的影响，针对男孩和女孩分别研究了屏幕时间（包括智能手机的屏幕时间）与儿童超重/肥胖之间的关联。对 2,242 名 10-14 岁日本儿童（1,278 名女孩）进行了横断面研究。超重/肥胖由国际肥胖工作组定义。Logistic回归分析显示，仅对于女孩来说，与<2小时相比，总ST（≥4小时）、智能手机ST（≥3小时）和非智能手机ST（≥2小时）均与超重/肥胖独立且显着相关。总 ST、不使用智能手机以及 <1 小时非智能手机 ST。因此，智能手机 ST ≥3 小时和非智能手机 ST ≥2 小时仅与女孩超重/肥胖相关。智能手机 ST ≥3 小时和非智能手机 ST ≥2 小时的女孩超重/肥胖的可能性是两者均较少使用的女孩的 6.79 倍 (95% CI: 3.11–14.81)。在女孩中，当总 ST ≥4 < 5 小时或智能手机 ST ≥2 小时时，当体力活动≥60 分钟/天且睡眠时间≥8.5 小时时，与超重/肥胖的显着相关性消失。此外，这些关联在男孩中都不显着。在日本女孩中，智能手机 ST、非智能手机 ST 和总 ST 均与超重/肥胖显着相关。为避免超重/肥胖，建议将智能手机 ST、非智能手机 ST 和总 ST 分别控制在 <3 小时、<2 小时和 <4 小时，并进行充足的体力活动和睡眠时间。