Many literature reviews summarized relationships between screen time and child health, but they only included a few studies conducted in Chinese children and adolescents. The potential influence of screen time may vary by social context.
(2022) 22:810 Zhang et al BMC Public Health https://doi.org/10.1186/s12889-022-13155-3 Open Access RESEARCH Screen time and health issues in Chinese school‑aged children and adolescents: a systematic review and meta‑analysis Youjie Zhang*, Shun Tian, Dan Zou, Hengyan Zhang and Chen‑Wei Pan* Abstract Backgrounds: Many literature reviews summarized relationships between screen time and child health, but they only included a few studies conducted in Chinese children and adolescents The potential influence of screen time may vary by social context The current systematic review and meta-analysis aimed to evaluate relationships between screen time and health issues among Chinese school-aged children and adolescents Methods: Peer-reviewed articles written in Chinese and English were retrieved from CNKI, Wanfang, PubMed, Embase, and Web of Science from inception to June 2020 The Downs & Black checklist was applied to assess study quality Meta analyses used random effect models and mixed effects model to calculate pooled adjusted odds ratios and 95% confidence intervals Heterogeneity, sensitivity, and publication bias were assessed using Q and I2 statistics, “one-study removed” analysis, the funnel plot, trim and fill analysis, and classical fail-safe N, respectively Results: In total, we identified 252 articles reporting 268 studies with unique samples These studies investigated relationships between screen time and health issues of adiposity, myopia, psycho-behavioral problems, poor aca‑ demic performance, cardiometabolic disease risks, sleep disorder, poor physical fitness, musculoskeletal injury, sub-health, and miscellaneous issues of height and pubertal growth, injury, sick leave, and respiratory symptoms Proportions of studies reporting positive relationships with screen time were lowest in adiposity (50.6%) and higher in myopia (59.2%) and psycho-behavioral problems (81.8%) Other health issues were examined in 10 or less studies, all of which had more than half showing positive relationships The pooled odds ratio from 19 studies comparing health risks with the screen time cutoff of 2 hours per day was 1.40 (95% CI: 1.31 to 1.50, I2 = 85.9%) The pooled effect size was 1.29 (95% CI: 1.20 to 1.39) after trimming studies for publication bias adjustments Conclusions: Findings exclusively generated from Chinese school-aged children and adolescents resonate those mainly from western countries Evidence suggests that higher levels of screen time are related with greater risks of various health issues, although the relationships appear to be weak and intertwined with other confounding factors Future studies need to investigate health-specific dose effects and mechanisms of screen time Keywords: Screen time, Child health, Chinese, Child, Adolescent *Correspondence: ujzhang@suda.edu.cn; pcwonly@gmail.com School of Public Health, Medical College of Soochow University, 199 Ren Ai Road, 215123 Suzhou, Jiangsu, China Background Electronic devices have become daily essentials in the modern days even for the young Children and adolescents spend more time on screen-based activities than ever before [1, 2] Concerns over the adverse effects of screen time have increased Several authoritative © The Author(s) 2022 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ The Creative Commons Public Domain Dedication waiver (http://creativeco mmons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data Zhang et al BMC Public Health (2022) 22:810 organizations have published guidelines for professionals and families to manage screen time for children and adolescents [3–7] The well-known recommendation is to have no more than 2 h of recreational screen time per day [7] However, evidence on the unfavorable relationships between excessive screen time and various health risks remain limited due to inconsistent research findings and unclear threshold effects [8] Current evidence on the potential impact of screen time has been majorly summarized from studies conducted in highincome Western countries [9, 10] Evidence from other regions may make additional contributions to the existing knowledge base [11, 12] In China, children and adolescents’ screen time have increased significantly [13] According to a 2016 national report, 36.8% of school-aged children from to 12 grades spent more than 2 h of screen time per day [14] Considering the concurrent rises of pediatric obesity, myopia, and mental health problems among Chinese youth [15–17], a considerable number of studies examined the potential health impact of screen time But these studies are not captured in existing reviews Chinese children and adolescents live in an environment where is culturally, socially, and physically different from the West Two significant differences make the investigation on Chinese youth’s screen time unique One is the prolonged overall sedentary time; the other is the relatively isolated cyberspace One widely recognized adverse health feature of screen time is being sedentary An international study found that Chinese 9- to 11-year-olds had the highest presence of “sitters” characterized by high sedentary time and low physical activity in both boys and girls as compared to the averages of children from 12 nations (boys: 56% vs 27%, girls: 59% vs 32%) [18] This is largely due to the nationwide academic devotions [19] The influence of screen time on sedentism-related health issues among a population with prolonged sedentary time would add additional insights In terms of the influence related to content exposure, Chinese children and adolescents live in a digital environment which is separated from the rest of the world due to the language barrier and internet censorship It would be interesting to examine whether similar relationships between screen time and health issues exist among Chinese youth as compared to counterparts living in western countries Systematic reviews are unbiased comprehensive syntheses of scholarly investigations on well-defined research questions, which also enable meta-analyses of statistical results of different studies On the topic of screen timerelated health influences, many systematic reviews have been conducted For example, Stiglic and Viner identified 13 systematic reviews, published till 2018, on the wellbeing effects of screen time in children and adolescents Page of 12 [8] Thereafter, at least seven systematic reviews have expanded on this topic [20–26] Health issues addressed in these reviews included body composition, dietary intake, mental health, cardiovascular risks, fitness, sleep, pain, asthma, myopia, and language skills Among these health issues, adiposity and depressive symptoms have shown relatively stronger evidence for associations with screen time, while evidence on other health issues is insufficient Despite the plethora of reviews, only a few studies conducted in China were included, which is far less than the number of studies found in our preliminary search Therefore, with the purpose of addressing this evidence gap, the current systematic review aimed to (1) identify studies examining relationships between screen time and health issues among Chinese school-aged children and adolescents from both Chinese and English literature databases, (2) summarize health issues that showed associations with screen time, and (3) use available data to quantify the relationship between screen time and child health Findings gather in this review can supplement the existing evidence bank from a population-specific perspective and offer insights for advancing screen timerelated health research Methods Search strategy Articles written in Chinese were retrieved from the China National Knowledge Infrastructure (CNKI) and Wanfang Data platforms which host the most comprehensive lists of Chinese academic journals and offer the largest access to full-text Chinese journal articles Articles written in English were searched from PubMed, Embase, and Web of Science databases Search terms were combinations of terms related to school-aged children and adolescents, screen-based behaviors, and geographic locations of mainland China, Hongkong, Macau and Taiwan (Table A.1) No limits were imposed on the publication date, the final search was conducted on June 1, 2020 Inclusion and exclusion criteria Eligible studies were identified according to the prespecified inclusion and exclusion criteria following the Population, Intervention, Comparison, Outcome, Study design (PICOS) framework [27] The inclusion criteria for study selection were (1) peer-reviewed articles written in Chinese or English, (2) study participants were children and adolescents with age ranges or mean ages between and 18 years, or enrolled in grade through grade 12, (3) observational or experimental study design, (4) study participants were not diagnosed with phycological or physical diseases at baseline, (5) studies reported relationships between screen time and certain Zhang et al BMC Public Health (2022) 22:810 health indicators Screen time refers to the time spent on screen-based behaviors [28] The current review did not confine to specific health outcomes and followed the World Health Organization’s definition of health that is “a state of complete physical, mental, and social wellbeing and not merely the absence of disease or infirmity” [29] Exclusive criteria were (1) conference abstracts and non-original research articles, (2) study participants were diagnosed with diseases at baseline, (3) repetitive publications, (4) studies that did not report relationships between screen time and health indicators, (5) crosssectional surveys reporting associations between screen time and internet addiction if measures of internet addiction included excessive screen time, (6) observational studies with sample sizes less than 300 and experimental studies with sample sizes less than 30 [30] Study selection and data extraction Entries identified from each bibliographic database were imported to EndNote™ 20 Duplicates were removed using the deduplication function of the program, and then manually checked by two reviewers (Y Z and S T.) Titles and abstracts of the remaining entries were screened by the two reviewers based on the pre-specified eligibility criteria Results from the preliminary screening were compared, and inconsistencies were discussed and resolved Full-text articles were obtained after the preliminary screening The two reviewers examined the full-texts independently and resolved discrepancies through intensive discussion Data extraction was performed by one reviewer (S.T., D.Z or H Z.) and checked by the other (Y Z.) Data extraction table included following information: the first author’s name, year of publication, journal, language written, location, research design, age range, sample size, types of screenbased behaviors, health issues, adjusted covariates, and main results (Table A.2) Quality assessment Study quality assessment was performed using the Downs & Black checklist [31] The checklist showed high reliability and validity, and was applied in several systematic reviews of health behaviors [30, 32, 33] The checklist can add up to a maximum score of 28 from 27 items assessing reporting quality, external validity of sample representativeness, internal validity of measurement and analytical biases, and selection bias The item of confounder adjustments has a maximum of points, point for the adjustment of sociodemographic variables and the other for the adjustments of bio-behavioral factors Two trained research assistants (D Z and H Z.) assessed the included studies independently, and a third researcher (Y.Z.) compared and resolved discrepancies The study Page of 12 quality scores were evaluated in three categories based on percentages of scores attained from the applicable items of corresponding study design: high (≥ 70%), moderate (50-69.9%), and low ( 50% indicated a substantial heterogeneity and the selection of the random effect model [34] Sensitivity of the meta-analysis was performed using the “one-study removed” analysis Assessments of publication bias included asymmetric examination of the funnel plot, Duval and Tweedie’s trim and fill analysis and the Classical fail-safe N (Duval & Tweedie, 2000) In addition, a mixed effects analysis was applied to generate subgroup effects by health issues using random effects models and combine effects from subgroups to yield an overall effect using a fixed effect model Results Search results An overview of the record retrieval and selection process is shown in Fig. A total number of 252 articles were retained for summative syntheses and data from 19 articles were pooled for meta-analyses The included articles were published between 1999 and 2020, 62.3% were published in 2015 and after, 80.2% were written in Chinese, and 92.5% were conducted in mainland China These articles reported original research findings regarding relationships between screen time and health issues of adiposity, myopia, psycho-behavioral problems, cardiometabolic disease risks, poor academic performance, sleep disorder, poor physical fitness, musculoskeletal injury, physical and mental sub-health, and a group of miscellaneous issues related to height or pubertal growth, injury, etc According to the health issues, 268 studies with independent samples were identified, nearly 90% of which were in a cross-sectional design (Table 1) The percentages of study quality classification are 8.6% (high), 57.5% (moderate), and 34.0% Zhang et al BMC Public Health (2022) 22:810 Page of 12 Fig. 1 The PRISMA flow diagram (low) Detailed study quality classification by health issues is shown in Table 2 Summary of study findings Among the 268 unique studies, the numbers and percentages reporting positive, negative, insignificant, and inconsistent relationships between screen time and health risks were 169 (63.1%), (0.3%), 35 (13.1%), and 63 (23.5%) Among the top-three most studied health issues, proportions of studies reporting positive relationships with screen time were lowest in adiposity (50.6%) and higher in myopia (59.2%) and psycho-behavioral problems (81.8%) Each of the other seven health issues had no more than 10 studies, and all had half or more showing positive relationships By research design, casecontrol studies had a highest proportion (13 out of 14) showing positive relationships between screen time and health risks, following cross-sectional studies (62.1%), longitudinal studies (6 out of 12), and intervention studies (1 out of 2) Counts of study findings by health issues and research design are shown in Table 3 Health issues without insignificant or inverse relationships with screen time were poor academic performance, sleep disorders, poor physical fitness, musculoskeletal injuries, and sub-health Inconsistent findings within studies were related to sample characteristics (sex, age, area of residence, etc.), device types (TV, computer, electronic games), purposes (recreational, educational), periods (weekend, weekday), or combinations of these attributes However, these inconsistencies did not demonstrate any clear pattern across studies Studies applied various ways to examine the does effect of screen time, such as cumulative sums and ordinal or binary categories with different cutoffs Lower ends of scree-time cutoffs in between-group comparisons that showed raised health risks are shown in Table 2 Zhang et al BMC Public Health (2022) 22:810 Page of 12 Table 1 Characteristics of eligible articles and identified studies Characteristics n Percentage Total number of articles 252 Language written Chinese 202 80.2 English 50 19.8 Mainland China 233 92.5 Hong Kong, Macau, or Taiwan 19 7.5 2015 ∼2020 2005 ∼ 2009 Location Year of publication 157 62.3 2010 ∼ 2014 66 26.2 21 8.3 1999 ∼ 2004 3.2 Total number of studies 268 Health issue Pooled effect sizes Three case-control and 16 cross-sectional studies provided 21 unique and valid adjusted odds ratios (ORs) of health risk comparisons using the screen time cutoff of 2 h per day Not all health issues were included in the meta-analyses, because there were less than two studies with valid ORs per health issue Within-study heterogeneity statistics were Q = 141.59, df (Q) = 20, P