Screen time, body mass index and neck circumference: is there an association with social class in children?

Abstract Life habits during childhood are decisive for future health conditions. The aim of this study was to evaluate screen time and anthropometry of children enrolled in municipal schools in the interior of the State of São Paulo. A cross-sectional study was carried out with students from 9 to 10 years of age from a city in the State of São Paulo, Brazil. A socioeconomic questionnaire validated by the Brazilian Association of Research Companies was used, containing also the determination of screen time (TV, video game, computer and cell phone), recommended by the Pediatrics Society. Anthropometry data was collected according to the Lohmam Anthropometric Standardization Reference Manual and compared to the z-score level with the WHO 2007. For the statistical analysis, Kruskal-Wallis, Chi-square or Fisher’s Exact tests were used.The confidence level was at 95%. Out of the 703 schoolchildren assessed, 97.44% had adequate height, 59.17% eutrophy BMI and 30.44% overweight. There was a correlation between BMI and non-stratified social class (p=0.038) and BMI and neck circumference (NC) (p<0.001).The z-score of the BMI showed that children with weight loss stayed longer watching TV (p=0.0486). The gender comparison showed that girls of higher social class stayed longer at the computer (p=0.0351) and using the cell phone (p<0.0001),and boys playing videogame (p=0.0005). Overweight and weight loss shown in the positive correlation between BMI and NC, although on opposite sides, were associated with screen time and especially with TV in children of higher social class.

摘要：儿童时期的生活习惯对其未来健康状况具有决定性影响。本研究旨在评估巴西圣保罗州内陆地区市属学校学生的屏幕使用时长与人体测量学（anthropometry）指标。本研究为横断面研究（cross-sectional study），研究对象为巴西圣保罗州某城市9至10岁的在校学生。研究采用经巴西研究公司协会（Brazilian Association of Research Companies）验证的社会经济状况问卷，该问卷同时涵盖由儿科学会推荐的屏幕使用时长相关调查内容，涉及电视、电子游戏、电脑及手机四类场景。人体测量学数据依照《Lohman人体测量标准化参考手册》进行采集，并与世界卫生组织2007年标准的z评分（z-score）进行比对分析。统计分析采用Kruskal-Wallis检验（Kruskal-Wallis test）、卡方检验（Chi-square test）及Fisher确切概率法（Fisher’s Exact test），检验置信水平设为95%。本次共评估703名学龄儿童，其中97.44%身高达标，59.17%的儿童身体质量指数（Body Mass Index, BMI）处于营养正常状态，30.44%存在超重情况。研究发现，BMI与未分层社会阶层（p=0.038）、BMI与颈围（neck circumference, NC）（p<0.001）均存在显著相关性。BMI的z评分结果显示，体重偏低的儿童看电视的时长更长（p=0.0486）。性别分层比较结果显示，社会阶层较高的女孩使用电脑（p=0.0351）及手机（p<0.0001）的时长更长，而男孩则更频繁地玩电子游戏（p=0.0005）。尽管超重与体重偏低分别与BMI和颈围呈正相关，但二者均与屏幕使用时长存在关联，尤其在社会阶层较高的儿童群体中，这种关联在电视使用场景中表现得尤为显著。