Physical activity and sedentary behavior among Chinese children aged 6-17 years: a cross-sectional analysis of 2010-2012 China National Nutrition and health survey

Physical activity and recreational screen time among Chinese children and adolescents: a national cross-sectional study

Background

The increasing prevalence of physical inactivity and prolonged Recreational Screen Time (RST) among children and adolescents is emerging as a significant public health concern. This study investigates the current status of Physical Activity (PA) and RST among Chinese children and adolescents from 2017 to 2019. It also examines variations in PA and RST across different school levels, genders, urban-rural areas, regions, and seasons.

Methods

A national cross-sectional survey, conducted in China from 2017 to 2019, included 53,101 children and adolescents from grades 4 to 12 (aged 10 to 18 years old). Data on PA and RST were collected via self-administered questionnaires. The study employed descriptive statistics, calculated weighted prevalence rates, and conducted differential analysis across diverse demographic groups.

Results

Between 2017 and 2019 in China, merely 28.73% of children and adolescents adhered to World Health Organization's PA guidelines, while 76.09% met China's RST guidelines. Notably, females, higher-grade students, rural residents, and children and adolescents from southern regions exhibited significantly lower levels of PA compared to their male, lower-grade, urban, and northern counterparts. Concurrently, RST was significantly higher among males, lower-grade students, rural residents, and those from northern regions. Seasonal variations were also observed, with lower PA and higher RST in autumn and winter as compared to spring.

Conclusion

The study reveals a concerning low level of PA among Chinese children and adolescents, with marked disparities in PA and RST across different groups. This underscores the need for targeted health promotion strategies to enhance PA and mitigate RST among various child and adolescent populations.

Effects of greenness in university campuses on test anxiety among Chinese university students during COVID-19 lockdowns: a correlational and mediation analysis

The purpose of this study is to investigate the correlations of greenness exposure with test anxiety among university students during COVID-19 lockdowns and to explore their mechanisms. We conducted a cross-sectional study with 2609 university students in Anhui and Shandong provinces, China. We assessed perceived campus greenness using a five-point Likert scale for quality, visibility, abundance, usage, and accessibility. Objective greenness was estimated via average normalised difference vegetation index (NDVI) in 1,000-, 1,500-, and 2,000-m radius zones around each of the campuses. A generalised linear mixed model examined the associations between greenness and test anxiety and to evaluate the mediation effects of physical activity, body mass index (BMI), and air pollution. Results showed that higher NDVI1500-m correlated with lower test anxiety (OR = 0.871; 95% CI: 0.851, 0.891), physical activity may partially mediate this association. Increased campus greenness may alleviate test anxiety among Chinese university students.

The impact of the world's first regulatory, multi-setting intervention on sedentary behaviour among children and adolescents (ENERGISE): a natural experiment evaluation

BACKGROUND

Regulatory actions are increasingly used to tackle issues such as excessive alcohol or sugar intake, but such actions to reduce sedentary behaviour remain scarce. World Health Organization (WHO) guidelines on sedentary behaviour call for system-wide policies. The Chinese government introduced the world's first nation-wide multi-setting regulation on multiple types of sedentary behaviour in children and adolescents in July 2021. This regulation restricts when (and for how long) online gaming businesses can provide access to pupils; the amount of homework teachers can assign to pupils according to their year groups; and when tutoring businesses can provide lessons to pupils. We evaluated the effect of this regulation on sedentary behaviour safeguarding pupils.

METHODS

With a natural experiment evaluation design, we used representative surveillance data from 9- to 18-year-old pupils before and after the introduction of the regulation, for longitudinal (n = 7,054, matched individuals, primary analysis) and repeated cross-sectional (n = 99,947, exploratory analysis) analyses. We analysed pre-post differences for self-reported sedentary behaviour outcomes (total sedentary behaviour time, screen viewing time, electronic device use time, homework time, and out-of-campus learning time) using multilevel models, and explored differences by sex, education stage, residency, and baseline weight status.

RESULTS

Longitudinal analyses indicated that pupils had reduced their mean total daily sedentary behaviour time by 13.8% (95% confidence interval [CI]: -15.9 to -11.7%, approximately 46 min) and were 1.20 times as likely to meet international daily screen time recommendations (95% CI: 1.01 to 1.32) one month after the introduction of the regulation compared to the reference group (before its introduction). They were on average 2.79 times as likely to meet the regulatory requirement on homework time (95% CI: 2.47 to 3.14) than the reference group and reduced their daily total screen-viewing time by 6.4% (95% CI: -9.6 to -3.3%, approximately 10 min). The positive effects were more pronounced among high-risk groups (secondary school and urban pupils who generally spend more time in sedentary behaviour) than in low-risk groups (primary school and rural pupils who generally spend less time in sedentary behaviour). The exploratory analyses showed comparable findings.

CONCLUSIONS

This regulatory intervention has been effective in reducing total and specific types of sedentary behaviour among Chinese children and adolescents, with the potential to reduce health inequalities. International researchers and policy makers may explore the feasibility and acceptability of implementing regulatory interventions on sedentary behaviour elsewhere.

Physical activity level correlates with obesity-related factors, but not with fundamental movement skills in preschool children: a cross-sectional study

This study aimed to examine the differences in physical activity (PA) level, fundamental movement skill (FMS), and obesity-related factors in preschoolers. A cross-sectional study was conducted in 426 preschool children aged 3-5 years. Participants were assigned to the low PA group (LPAG), moderate PA group (MPAG), and high PA group (HPAG) according to the total score obtained in the PA questionnaire for young children. FMS and obesity-related factors were also analyzed. PA was compared by age and sex, and FMS and obesity-related factors were compared between groups. Significant differences were found according to sex. Boys were more active than girls in the 3-4 years age group, but no significant differences were observed at the age of 5 years. LPAG showed lower FMS than MPAG and HPAG, although this was not statistically significant. However, body mass index (BMI), BMI z-score, body fat, and muscle mass showed significant differences in terms of PA levels. Consideration of age and sex is crucial in promoting PA among preschoolers. Additionally, better obesity-related factors are associated with higher PA levels, and FMS may be a useful tool in evaluating health and fitness.

Developing the theoretical model of Chinese physical education teachers' health communication competence: based on grounded theory

Background

Physical education teachers' health communication competence is a key factor in health promotion. Although health communication is a multidisciplinary field, medical practitioners are the primary focus of health communication research, whereas physical education teachers are marginalized. Therefore, this study proposes a theoretical model of health communication competence for physical education teachers.

Methods

This qualitative research utilized interviews as the primary data collection method. Purposeful sampling was employed to select participants, including university teachers, primary and secondary school teachers, and health education professionals from diverse regions of China. A total of 31 participants were interviewed through two focus groups (N = 15) and individual semi-structured interviews (N = 16). Grounded theory was used to analyze and code the collected interview materials.

Results

The health communication competence of physical education teachers consisted of three main categories, 10 subcategories, 30 concepts, and 240 statement labels. The three main categories were as follows: (i) foundations of health communication knowledge and skills (this category encompassed three subcategories, namely sport and health knowledge reserve, health beliefs, and health behaviors); (ii) health communication perception competence (this category included two subcategories, namely health risk and crisis perception competence and communication audience perception competence); and (iii) practical competence of health communication (this category consisted of five subcategories, namely language expression competence, organizational and design competence, utilization of new media tools competence, communication content selection and processing competence, and professional skills).

Conclusion

The theoretical model of health communication competence in this study provides a foundation for the involvement of physical education teachers in health communication work. It can serve as a reference for the development of both pre-service health education courses and in-service training systems for physical education teachers. Future research can expand the sample size and geographic coverage to further validate the applicability of the findings. Additionally, investigating the factors influencing the formation of the identified competencies is recommended.

Sleep Status Among Children and Adolescents Aged 6-17 Years - China, 2016-2017

What is already known about this topic?

There has been little to no description of sleep status among children and adolescents nationwide in recent years.

What is added by this report?

This report assesses the sleep duration and sleep patterns of children and adolescents in China. Approximately half of the adolescents did not get the recommended amount of sleep on school days, and more than half overslept on weekends.

What are the implications for public health practice?

The importance of children and adolescents meeting recommended sleep durations needs greater emphasis, especially among older age groups and those in urban areas.

Associations of greenness surrounding schools and self-reported depressive and anxiety symptoms in Chinese adolescents

BACKGROUND

The effect of school-based greenness exposure on mental health among adolescents remains unclear. The study aimed to estimate the associations between school-based greenness and depressive and anxiety symptoms among adolescents and explore potential modifier and mediator between the associations.

METHODS

A cross-sectional survey involving 15,559 adolescents was conducted in China. The Chinese version of the Center for Epidemiologic Studies Depression 9-Item Scale and the Generalized Anxiety Disorder 7-Item Scale were used to assess the depressive and anxiety symptoms among adolescents. The Normalized Difference Vegetation Index within a 400 m and 800 m zone surrounding schools was used to indicate the adolescents' exposure to greenness. We estimated daily concentrations of PM_1.0, PM_2.5, and NO₂ from the China High Air Pollutants dataset. Multiple logistic regression models were used.

RESULTS

Higher exposure to greenness surrounding schools was negatively associated with depressive (OR: 0.774, 95%CI: 0.685-0.875) and anxiety symptoms (0.740, 0.669-0.818). We observed stronger associations between greenness and depressive and anxiety symptoms among girls, lower age group (11-15 years), and adolescents born to parents with lower education levels. PM_1.0 (proportion mediated estimates: 14.3 %; 95 % CI: 4.2 %, 24.5 %) and PM_2.5 (10.5 %; 95 % CI: 3.0 %, 17.9 %) mediated the associations between greenness exposure and depressive symptoms. The number of days adolescents attended physical education classes per week mediated -22.8 % (95 % CI: -38.5 %, -7.1 %) and -9.7 % (95 % CI: -15.5 %, -3.8 %) of the effects of greenness on depressive and anxiety symptoms.

CONCLUSIONS

Increasing the greenness and improving the environment surrounding schools is effective in promoting the mental health of adolescents.

The Cumulative Effect of Multilevel Factors on Myopia Prevalence, Incidence, and Progression Among Children and Adolescents in China During the COVID-19 Pandemic

Purpose

To estimate the effects of school closures and associated lifestyle changes on myopia in Chinese children and adolescents during the coronavirus disease 2019 (COVID-19) pandemic.

Methods

Two cross-sectional surveys recruited 14,296 Chinese students aged 7 to 18 years in November 2019 and June 2020 from which an open cohort study (nested queue design) was derived and used to assess myopia prevalence, incidence, and progression rates (defined as students with progression in myopia severity at the second survey wave among those with myopia at baseline). The severity of myopia was determined by measurements of visual acuity (<5.0) and noncycloplegic refraction (spherical equivalent <-0.50 diopters). Twenty-three myopia-influencing factors were divided into three categories: eye-use habits, lifestyle, and family and subjective factors. Responses to each of these 23 factors were labeled as either positive or negative options and then combined to generate a comprehensive score.

Results

Boys and girls were equally represented (50%) and had the same average age (11.5 years) at each wave. The myopia prevalence increased from 48.2% to 60.0%, with 27.1% myopia incidence and 13.2% myopia progression rates for Chinese children and adolescents. Each of the 23 factors was associated with myopia prevalence but had no significant effect on myopia incidence or progression. However, these 23 factors had a cumulative effect on myopia risks; higher scores were associated with more positive factors and lower risk ratios of myopia and vice versa. Except for the progression rate, the myopia prevalence and incidence and risk ratios decreased with higher comprehensive scores.

Conclusions

School closures during the COVID-19 pandemic increased the risk of myopia in Chinese children and adolescents due to the accumulation of poor eyesight habits, unhealthy lifestyles, and excessive screen time.

Translational Relevance

Rather than focusing on single risk factors for myopia, future myopia prevention strategies should focus on integrating multiple comprehensive approaches across schools, families, and communities.

Chemical constituents of ambient fine particulate matter and obesity among school-aged children: A representative national study in China

BACKGROUND

Studies show that fine particulate matter (PM_2.5) contributes to childhood obesity. However, evidence on the effects of its constituents on obesity has not been explored.

METHODS

Using multistage stratified cluster sampling, we enrolled 41,439 school-age children (aged 6-17 years) from a representative nationwide survey of 30 provinces in China (mean age ± standard deviation: 12.0 ± 3.3 years). Weight and height were measured using a physician beam scale with a height rod, and covariates were determined using a standard questionnaire. The concentration of PM_2.5 chemical constituents was estimated by a chemical transport (GEOS-Chem) model using input satellite data and ground-based observations. The constituents included black carbon, ammonium, nitrate, organic matter, sulfate, and soil dust. Generalized linear models were used to estimate the association between the chemical constituents of PM_2.5 and obesity.

RESULTS

A positive association between the constituents of PM_2.5 and obesity were observed. Children were more susceptible to black carbon than other species. A 1-μg/m³ increase in black carbon led to a 0.079 (95 % confidence interval [CI]:0.028, 0.130)-kg/m² increase in body mass index (BMI). This also increased the odds of being obese and overweight to 1.174 (95 % CI: 1.111, 1.240) and 1.165 (95 % CI: 1.116, 1.216), respectively. Stratified analyses showed that the effects were stronger in girls and older children, as well as in urban and Northeast regions. The effect of the PM_2.5 constituents on obese and overweight children from urban areas significantly interacted with that of rural areas.

CONCLUSIONS

The PM_2.5 constituents were associated with an increased BMI and childhood obesity. Further studies are warranted to validate these results and clarify their potential mechanisms. We suggest focusing on black carbon and Northeast regions.

The influence of sedentary behaviour on mental health among children and adolescents: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Systematic reviews that have examined associations between sedentary behaviour (SB) and mental health among children and adolescents are mainly based on cross-sectional investigations. There is a lack of evidence for a prospective relationship between SB and mental health in children and adolescents. This systematic review synthesized longitudinal studies that examined prospective associations between SB and mental health among children and adolescents.

METHODS

We conducted computer searches for English language literature from electronic databases of PubMed, Embase, PsycInfo and Google scholar, and manually screened the references of existing relevant studies to select studies for the synthesis. We included observational longitudinal studies that assessed the association between SB and mental health among children and adolescents. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

In total, 58 longitudinal studies met the inclusion criteria and were synthesized in the review. We found that higher SB among children and adolescents was associated with increased depression, anxiety and other mental health problems later in life. A dose-response association between SB and mental health was observed, suggesting that children and adolescents who spend more time on SB may have a higher risk of developing poorer mental health later.

CONCLUSIONS

The findings in the present study suggest that intervention programs targeting reducing SB may benefit to the prevention of poor mental health among children and adolescents. Future intervention studies especially randomized controlled trials are needed to elucidate a causal relationship between SB and mental health among children and adolescents.

Functional Training Focused on Motor Development Enhances Gross Motor, Physical Fitness, and Sensory Integration in 5-6-Year-Old Healthy Chinese Children

OBJECTIVE

Physical inactivity and sensory integration dysfunction are public health concerns among Chinese preschool children. The purpose of this study was to determine the efficacy of a novel functional training program focused on motor development for healthy children aged 5 to 6 years.

METHODS

A total of 101 healthy children aged 5 to 6 years in Tianjin were randomly assigned to the experimental group (N = 51), which received 12-week functional training featuring essential motor skills, whilst the control group (N = 50) continued with their kindergarten-based physical education curriculum. Test of Gross Motor Development-2, national physical fitness measurement, and sensory integration were evaluated before and after the intervention. Children's height, body weight, and the corresponding pre-intervention test scores were utilized as covariates to compare the post-intervention outcomes between the groups.

RESULTS

After the intervention, the experimental group scored considerably higher (P < 0.01) on the locomotor composite score, object control composite score, and overall gross motor score than the control group; the experimental group scored higher (P < 0.05) on the run, gallop, leap, stationary dribble, kick, striking a stationary ball, overhand throw, and underhand roll motor skill tests than the control group; the experimental group performed considerably better (P < 0.01) on the balance beam walking test and sit-and-reach test than the control group; and, the experimental group performed considerably better (P < 0.01) on the vestibular function, tactile defensiveness, and proprioception than the control group.

CONCLUSION

A 12-week functional training focused on motor development effectively enhanced gross motor, physical fitness, and sensory integration in 5-6-year-old healthy Chinese children.

Current Assessment of Weight, Dietary and Physical Activity Behaviors among Middle and High School Students in Shanghai, China-A 2019 Cross-Sectional Study

Poor nutrition or insufficient physical activity (PA) are risk factors for obesity and chronic diseases. This 2019 cross-sectional study from the school health survey examined the dietary and PA behaviors of Chinese adolescents. A total of 12,860 adolescents aged 11–18 participated through multistage and stratified cluster random sampling. A questionnaire collected data on weight, PA, sedentary lifestyle, and eating habits. Unhealthy behaviors were identified and summed up for each behavior. Participants were then classified into high and low amounts of risk behaviors. Weight status was defined using Body Mass Index (BMI) cutoff points for Chinese individuals aged 6–18. Multinomial logistic regression was used to assess effects of lifestyle behaviors on weight status. The prevalence of overweight and obesity was 22.3% among all participants (30.6% in boys, 13.2% in girls). Females engaged in more risk physical activities (4.12 vs. 3.80, p < 0.05), while males engaged in more risk dietary activities (2.20 vs. 2.02, p < 0.05). Higher number of risk dietary, PA, and sedentary behaviors were all significantly correlated with higher BMI (dietary: r = 0.064; PA: r = 0.099; sedentary: r = 0.161; p < 0.001 for all) and body weight (dietary: r = 0.124; PA: r = 0.128; sedentary: r = 0.222; p < 0.001 for all). Risk sedentary behaviors was a significant risk factor for overweight/obesity (Adjusted Odds Ratio AOR = 1.30, 95% Confidence Interval CI 1.11–1.52). Obesity and unhealthy lifestyle behaviors remain a concern among Chinese adolescents. These results provide an update on the factors contributing to overweight/obesity among adolescents and call for efforts to address obesity among adolescents.

Greenness surrounding schools and adiposity in children and adolescents: Findings from a national population-based study in China

BACKGROUND

Previous studies have indicated that exposure to green space may benefit human health. However, the available evidence concerning the effects of greenness, especially school-based greenness, on pediatric obesity is scarce.

OBJECTIVE

To explore the association between school-based greenness and adiposity in children and adolescents in China.

METHOD

We conducted a nationwide cross-sectional study of 56,620 children and adolescents (aged 6-18 years) in seven provinces/municipalities across China. School-based greenness was assessed using satellite-derived Normalized Difference Vegetation Index (NDVI) and Soil Adjusted Vegetation Index (SAVI) within 100-, 500-, and 1000-m circular buffers around each school's address. Generalized linear mixed regression models were used to estimate associations of greenness with BMI z-scores (zBMI), waist circumference, and prevalent overweight/obesity. We also explored the potential mediating role of ambient air pollution and physical activity in the greenness-adiposity associations.

RESULT

In the adjusted model, an IQR increase in NDVI_-1000m was associated with lower zBMI (β: -0.11, 95% confidence interval[CI]: -0.13,-0.09) and waist circumference (β: -0.64, 95%CI: -0.78,-0.50). Consistently, an IQR increase in NDVI_-100m, NDVI_-500m, NDVI_-1000m was associated with 7-20% lower odds of overweight/obesity in the adjusted models. Air pollutants mediated 6.5-29.1% of the association between greenness and zBMI. No significant mediation effect was observed for physical activity.

CONCLUSION

Higher school-based greenness levels were associated with lower zBMI, waist circumference, and lower odds of overweight and obesity in children and adolescents. Ambient air pollutants may partially mediate the greenness-adiposity associations.

Physical activity and health in Chinese children and adolescents: expert consensus statement (2020)

China is experiencing significant public health challenges related to social and demographic transitions and lifestyle transformations following unprecedented economic reforms four decades ago. Of particular public health concern is the fourfold increase in overweight and obesity rates in the nation's youth population, coupled with the low prevalence of adolescents meeting recommended levels of physical activity. Improving the overall health of China's more than 170 million children and adolescents has become a national priority. However, advancing nationwide health initiatives and physical activity promotion in this population has been hampered by the lack of a population-specific and culturally relevant consensus on recommendations for achieving these ends. To address this deficiency and inform policies to achieve Healthy China 2030 goals, a panel of Chinese experts, complemented by international professionals, developed this consensus statement. The consensus was achieved through an iterative process that began with a literature search from electronic databases; in-depth reviews, conducted by a steering committee, of the resulting articles; and panel group evaluations and discussions in the form of email correspondence, conference calls and written communications. Ultimately, the panel agreed on 10 major themes with strong scientific evidence that, in children and adolescents aged 6-17, participating in moderate to vigorous physical activities led to multiple positive health outcomes. Our consensus statement also (1) highlights major challenges in promoting physical activity, (2) identifies future research that addresses current knowledge gaps, and (3) provides recommendations for teachers, education experts, parents and policymakers for promoting physical activity among Chinese school-aged children and adolescents. This consensus statement aligns with international efforts to develop global physical activity guidelines to promote physical activity and health and prevent lifestyle-related diseases in children and adolescents. More importantly, it provides a foundation for developing culturally appropriate and effective physical activity interventions, health promotion strategies and policy initiatives to improve the health of Chinese children and adolescents.

Associations between daily ambient temperature and sedentary time among children 4-6 years old in Mexico City

BACKGROUND

Sedentary behavior is a worldwide public health concern. There is consistent and growing evidence linking sedentary behavior to mortality and morbidity. Early monitoring and assessment of environmental factors associated with sedentary behaviors at a young age are important initial steps for understanding children's sedentary time and identifying pertinent interventions.

OBJECTIVE

This study examines the association between daily temperature (maximum, mean, minimum, and diurnal variation) and all-day sedentary time among 4-6 year old children in Mexico City (n = 559) from the year 2013 to 2015.

METHODS

We developed a spatiotemporally resolved hybrid satellite-based land use regression temperature model and calculated percent daily sedentary time from aggregating 10-second epoch vertical counts captured by accelerometers that participants wore for one week. We modeled generalized additive models (GAMs), one for each temperature type as a covariate (maximum, mean, minimum, and diurnal variation). All GAMs included percent all-day sedentary time as the outcome and participant-level random intercepts to account for repeated measures of sedentary time. Our models were adjusted for demographic factors and environmental exposures.

RESULTS

Daily maximum temperature, mean temperature, and diurnal variation have significant negative linear relationships with all-day sedentary time (p<0.01). There is no significant association between daily minimum temperature and all-day sedentary time. Children have on average 0.26% less daily sedentary time (approximately 2.2 minutes) for each 1°C increase in ambient maximum temperature (range 7.1-30.2°C), 0.27% less daily sedentary time (approximately 2.3 minutes) for each 1°C increase in ambient mean temperature (range 4.3-22.2°C), and 0.23% less daily sedentary time (approximately 2.0 minutes) for each 1°C increase in diurnal variation (range 3.0-21.6°C).

CONCLUSIONS

These results are contrary to our hypothesis in which we expected a curvilinear relationship between temperature (maximum, mean, minimum, and diurnal variation) and sedentary time. Our findings suggest that temperature is an important environmental factor that influences children's sedentary behavior.

Association between exposure to fine particulate matter and obesity in children: A national representative cross-sectional study in China

BACKGROUND

Childhood obesity is a global health issue, and limited evidence suggests that air pollution may be a contributing factor. This study aims to examine whether exposure to fine particulate matter (PM_2.5) is associated with obesity status in a nationally representative sample of schoolchildren in China.

METHODS

The study population consisted of 41,439 schoolchildren of 6-17 years old, recruited from 30 provinces in China using a multi-stage stratified sampling method. Weights and heights were measured for all the participants, and sociodemographic information was collected using a questionnaire. The obesity status was classified following the Chinese national standards. The PM_2.5 exposure was estimated as the 5-year average concentration at the school location for each participant. The association between obesity status and PM_2.5 exposure was examined using weighted logistic regressions adjusted for potential confounders.

RESULTS

The prevalence of normal weight, overweight, and obesity were 78.5%, 12.4%, and 9.0%, respectively. PM_2.5 exposure averaged 59.8 ± 17.6 μg/m³ with a range of 30.5-115.2 μg/m³ among all the participants. The risk of obesity increased by 10.0% (95% confidence interval: 3.0-16.0%) per 10 μg/m³ increase in PM_2.5 exposure. The PM_2.5-associated risk was significantly elevated in older age groups and children living in urban areas (interaction p-values < 0.05).

CONCLUSIONS

This national survey revealed that approximately 1 in 5 Chinese schoolchildren were overweight or obese. Exposure to PM_2.5 in the ambient air was significantly associated with childhood obesity. The findings suggest the need for further research to uncover the roles of PM_2.5 exposure in childhood obesity development.

Association of Reallocating Time in Different Intensities of Physical Activity with Weight Status Changes among Normal-Weight Chinese Children: A National Prospective Study

Background: Time spent in different intensity-specific physical activities is codependent, but the substitution effect of different activities on weight status changes in children remains unclear. This study aims to investigate the prospective association between reallocating time in different intensities of physical activity and weight status changes among Chinese children. Methods: A national sample of 15,100 normal-weight children aged 7–18 years (46.7% boys) were recruited in September 2013 and followed up for nine months. Vigorous-intensity physical activity (VPA), moderate-intensity physical activity (MPA), walking, and sedentary time were obtained by International Physical Activity Questionnaire Short Form (IPAQ-SF). Height and weight were objectively measured, by which body mass index (BMI) and BMI z-score were calculated. Weight status was classified by the Chinese criteria for 7- to 18-year-old children. Isotemporal substitution analyses (including single-factor model, partition model, and isotemporal substitution model) were applied to examine the association of time allocation with weight status changes. Results: Each 30 min/day of increase in VPA was favorably associated with a 13.2% reduced risk of incident overweight/obesity in a single-factor model and a 15.6% reduced risk in a partition model. Negative associations were found between VPA, MPA, walking and the risk of being underweight in the single-factor model, but not in the partition model. In substitution models, replacing 30 min/day sedentary time with an equal amount of VPA was favorably associated with a 16.1% reduction of the risk of being overweight/obese. Conclusion: These findings highlight the need for promoting vigorous-intensity physical activity in children.

Prevalence of Physical Activity and Sedentary Behavior among Chinese Children and Adolescents: Variations, Gaps, and Recommendations

Physical-activity (PA) and sedentary-behavior (SB) assessment is of particular importance in the promotion of health in young people. However, there is no comprehensive overview of PA and SB from national surveys among Chinese children and adolescents. Following a literature search for Chinese national health surveys, 11 papers from six national surveys were found. Of the included studies, the majority applied self-reported questionnaires to estimate the prevalence of PA and SB. Owing to different definitions of the prevalence of PA and SB and various measures, a large variation in prevalence of PA and SB was observed. Such variations were attributable to methodological and practical issues. This study highlights the current gaps in estimating the national prevalence of PA and SB among Chinese children and adolescents, which should be addressed. To improve the quality of PA and SB surveillance, standardized measurement protocols to estimate the prevalence of PA and SB more accurately among Chinese children and adolescents are urgently required.