Device-measured sedentary time in Norwegian children and adolescents in the era of ubiquitous internet access: secular changes between 2005, 2011 and 2018

Provided and received positive and negative social control, relationship satisfaction, and sedentary behavior in parent-child dyads

BACKGROUND

The close relationship processes and health model and the dyadic health influence model posit that relationship beliefs (eg, relationship satisfaction) and influence strategies (eg, provision and receipt of positive and negative social control) mediate health behavior change. However, evidence for such mediation in parent-child dyads is limited.

PURPOSE

Two complementary mediation hypotheses were tested: (1) social control forms indirect relationships with sedentary behavior (SB), via relationship satisfaction acting as a mediator; and (2) relationship satisfaction forms indirect relationships with SB, with social control operating as a mediator.

METHODS

Data from 247 parent-child dyads (9- to 15-year-old children) were analyzed using manifest mediation models. SB was measured with GT3X-BT accelerometers at Time 1 (T1; baseline) and Time 3 (T3; 8-month follow-up). Relationship satisfaction and social control were assessed at T1 and Time 2 (T2; 2-month follow-up). Path analysis models, controlling for baseline SB, were fit.

RESULTS

Received positive control (children, T1) was associated with higher relationship satisfaction in both children and parents (T2), which in turn were related to lower and higher parental SB at T3, respectively. Provided positive control (parents; T1) was related to higher SB (T3) in children. Relationship satisfaction among children (T1) predicted higher levels of received positive and negative control (children, T2).

CONCLUSIONS

Provided and received positive social control may form direct and indirect associations with SB in parent-child dyads. Future research may need to consider further subtypes of positive control, which may explain the divergent effects of this form of control on SB.

Recent trends and disparities in screen-based sedentary behavior and physical activity among U.S. overweight youth, 2018-2022

BACKGROUND

Sedentary behavior (SB) and physical activity (PA) are crucial factors influencing health outcomes in overweight children and adolescents. However, recent changes in SB and PA trends among U.S. overweight youth have not been well described, limiting the development of evidence-based clinical and public health interventions.

METHODS

Serial, cross-sectional analyses were conducted using data from the National Survey of Children's Health (NSCH) on U.S. overweight youth aged 6-17 years, spanning from 2018 to 2022. Linear regression models were employed to analyze time trends, with survey year as the exposure and recreational screen time (ST), adherence to the ≤2 h/day ST guideline, and adherence to the ≥1 h/day PA guideline as the outcomes. Multivariable-adjusted logistic and linear regressions were used to evaluate trends, adjusting for age group, sex, race/ethnicity, household income, and the highest education level of primary caregivers.

RESULTS

Data from 11,865 individuals (mean age 12.3 years [SD 2.9]; 6417 [52.3 %] girls) were analyzed. From 2018 to 2022, the average ST duration among overweight youth increased from 3.7 h to 4.1 h per day, a statistically significant increase (p = 0.07). The estimated prevalence of overweight youth meeting the ≤2 h/day ST guideline decreased from 44.6 % to 30.0 % (p = 0.007). Additionally, the prevalence of meeting the ≥1 h/day PA guideline remained low and stable, ranging from 8.4 % to 12.3 % during the analysis period (p = 0.6).

DISCUSSION

In this nationally representative sample of U.S. overweight youth, ST increased by nearly 0.4 h/day over the five-year observation period, while adherence to the ≤2 h/day ST guideline decreased. Adherence to the ≥1 h/day PA guideline remained consistently low. These patterns were consistent across sociodemographic subgroups (age group, sex, ethnicity, and household income). These findings underscore the need for enhanced public health initiatives targeting U.S. youth to reduce recreational screen time and promote a physically active lifestyle.

Device-measured physical activity and sedentary time in the Nordic countries: A scoping review of population-based studies

PURPOSE

The purpose of this scoping review was to summarize and describe the methodology and results from population-based studies of physical activity and sedentary time measured with devices in the Nordic countries (Denmark, Finland, Iceland, Norway, and Sweden) and published in 2000 or later.

METHODS

A systematic search was carried out in PubMed and Web of Science in June 2023 using predefined search terms.

RESULTS

Fourteen unique research projects or surveillance studies were identified. Additionally, 2 surveillance studies published by national agencies were included, resulting in a total of 16 studies for inclusion. National surveillance systems exist in Finland and Norway, with regular survey waves in school-aged children/adolescents and adults. In Denmark, recent nationally representative data have been collected in school children only. So far, Sweden has no regular national surveillance system using device-based data collection. No studies were found from Iceland. The first study was conducted in 2001 and the most recent in 2022, with most data collected from 2016 to date. Five studies included children/adolescents 6-18 years, no study included preschoolers. In total 11 studies included adults, of which 8 also covered older adults. No study focused specifically on older adults. The analytical sample size ranged from 205 to 27,890. Detailed methodology is presented, such as information on sampling strategy, device type and placement, wear protocols, and physical activity classification schemes. Levels of physical activity and sedentary time in children/adolescents, adults, and older adults across the Nordic countries are presented.

CONCLUSION

A growing implementation of device-based population surveillance of physical activity and sedentary behavior in the Nordic countries has been identified. The variety of devices, placement, and data procedures both within and between the Nordic countries highlights the challenges when it comes to comparing study outcomes as well as the need for more standardized data collection.

Impact of a nationwide school policy on body mass index in Danish school children: An interrupted time series analysis

Objectives

A new school policy mandating 45 min physical activity daily during school was introduced in Denmark in 2014. We aimed to evaluate the effect of this policy on BMI in school-aged children. It was hypothesized that the school policy would decrease BMI, especially in the obese fraction of the population (90th percentile BMI).

Study design

This register-based study was conducted as a natural experiment.

Methods

Analyses were based on data from The National Child Health Register that contains nationwide data on height and weight from mandatory preventive health examinations completed by school nurses or medical doctors during pre-preparatory classes (0th-3rd grade) and lower secondary education (7th-9th grade). A total of 401,517 children were included in the analyses with annual repeated cross-sectional data covering the period from 2012 to 2018. The effect of the school policy was evaluated using an interrupted time series approach comparing pre- and post-policy slopes in BMI, stratified by sex and age-group.

Results

In boys, no significant differences were observed in mean BMI slopes from pre-to post-policy in either age-group. In girls, post-policy slopes were significantly higher compared to pre-policy in both age-groups (0th-3rd grade: β:0·034 kg/m2, 95%-CI: (0·024; 0·043), p-value: <0·001; 7th-9th grade: β:0·066 kg/m2, 95%-CI: (0·028; 0·103), p-value: 0·001). No significant differences in slopes were observed in BMI at the 90th percentile from pre-to post-policy for both sexes and across both age-groups. Adjustment for leisure-time physical activity as a potential time-varying confounder did not alter the findings.

Conclusions

In conclusion, we did not detect a significant decrease in BMI levels among school-aged children following the introduction of a nationwide school policy specifying daily physical activity in school. If anything, a small positive change in BMI was observed in girls. More research is needed to understand whether structural changes similar to this requirement are able to prevent overweight and obesity in children and adolescents.

Sociodemographic disparities in sedentary time among US youth vary by period of the day

INTRODUCTION

Studies have reported sex and race/ethnicity disparities in sedentary time (ST), but none have evaluated ST by well-defined periods of the weekday (before school, during school, afterschool, and evening) and weekend day (morning, afternoon, and evening). Comparing sex and race/ethnicity disparities in ST at different periods of a weekday and weekend day can deepen our understanding of disparities and inform intervention efforts. This study tests sex and race/ethnicity disparities in ST by period of day in a representative sample of US youth.

METHODS

Youth (N = 2,972) from the 2003-2006 NHANES waves reported demographic variables and wore an accelerometer for 7 consecutive days to assess ST. Linear regressions were conducted to test relationships between sex and race/ethnicity and ST (min/hour) during each period of a weekday and weekend day. ST differences by sex and race/ethnicity were calculated to identify the periods of the day presenting the largest opportunity to reduce disparities.

RESULTS

Females were more sedentary than males during school (p < 0∙0001), afterschool (p < 0∙0001), and weekday evenings (p < 0∙0001) after controlling for covariates. After controlling for covariates, race/ethnicity only was a significant predictor of ST during weekend mornings (p < 0∙0001). During school and afterschool emerged as the periods with the largest opportunities to reduce sex disparities in ST. Weekend mornings were identified as the largest opportunity to reduce race/ethnic disparities in ST.

CONCLUSIONS

Sex disparities in ST appear to be driven mostly by the during school period of the day, while race/ethnic disparities in ST seem to be driven by the weekend morning period. Future intervention work should consider these periods when aiming to reduce ST disparities in youth.

Physical activity during early life and the risk of all-cause mortality in midlife: findings from a birth cohort study

BACKGROUND

The objective of this study was to examine the association between physical activity during childhood and adolescence and the risk of all-cause mortality in midlife. We analyzed data from a birth cohort (The 1958 National Child Development Survey), including births in England, Wales and Scotland.

METHODS

Physical activity was assessed using questionnaires at ages 7, 11 and 16. Death certificates defined all-cause mortality. Cumulative exposure, sensitive and critical periods, and physical activity trajectory from childhood to adolescence were tested using multivariate Cox proportional hazard models. The sweep the death was confirmed was defined as the time event.

RESULTS

From age 23 to 55, 8.9% of participants (n = 9398) died. Physical activity in childhood and adolescence affected the risk of all-cause mortality in midlife. In men, physical activity at ages 11 [hazard ratio (HR): 0.77; 95% confidence interval (CI): 0.60-0.98] and 16 (HR: 0.60; 95% CI: 0.46-0.78) was associated with reduced risk of all-cause mortality. In women, physical activity at age 16 (HR: 0.68; 95% CI: 0.48-0.95) was associated with reduced risk of all-cause mortality. Physical activity in adolescence eliminated the risk of all-cause mortality associated with physical inactivity in adulthood in women.

CONCLUSIONS

Physical activity during childhood and adolescence was associated with reduced risk of all-cause mortality with different effects by sex.

Effect of nationwide school policy on device-measured physical activity in Danish children and adolescents: a natural experiment

Background

A new Danish school policy with a requirement for 45 min physical activity daily during school hours was introduced in 2014. The objective of this natural experiment was to evaluate the effect of this nationwide school policy on physical activity in Danish children and adolescents.

Methods

Four historical studies completed between 2009 and 2012 comprised the pre-policy study population. Post-policy data were collected in 2017/18. All post-policy schools were represented in the four pre-policy studies. Age-groups and seasons were matched. In total, 4816 children and adolescents aged 6-17 were included in the analyses (2346 pre-policy and 2470 post-policy). Children and adolescents were eligible if they had accelerometer measurements and did not have any physical disabilities preventing activity. Physical activity was measured by accelerometry. Main outcome was any bodily movement. Secondary outcomes were moderate to vigorous physical activity and overall movement volume (mean counts per minute).

Findings

The school policy interrupted a linear decreasing pre-policy trend in physical activity during school hours. All activity outcomes increased post-policy during a standardized school day (8:10 am-1 pm). Increases were more pronounced in the youngest children. Specifically, we observed a daily increase during a standardized school day in 2017/2018 of 14.2 min of movement (95% CI: 11.4-17.0, p < 0.001), 6.5 min of moderate to vigorous physical activity (95% CI: 4.7-8.3, P < 0.001), and 141.8 counts per minute (95% CI: 108.5-175.2, P < 0.001).

Interpretation

A national school policy may be an important strategy to increase physical activity during school hours among children and adolescents.

Funding

The Danish Foundation TrygFonden has funded the PHASAR project (ID 115606).

Developmental disparities in sedentary time by period of the day among US youth: a cross-sectional study

Background

Definitive evidence shows sedentary time (ST) is an independent risk factor for chronic disease, irrespective of physical activity. Despite calls to limit youth ST, studies demonstrate a spike in ST at the transition from childhood to adolescence. Identifying periods of the day (e.g., before school, during school, afterschool, and evenings) during which ST is higher in adolescents vs. children—that is, specifying when within daily routines ST disparities emerge—may be important to inform intervention strategies, as periods of the day correspond with variations in setting and supervision. The purpose of this study was to examine device-assessed ST engagement by period of day and developmental stage in a nationally representative sample of United States youth.

Methods

Youth (N = 2,972 between 6–18 years) from the 2003–2004 and 2005–2006 waves of NHANES reported demographic variables and wore an accelerometer for seven consecutive days to determine ST. Linear regression analyses were applied to study associations between ST and developmental stage (childhood or adolescence) by period of the week and weekend days, while controlling for sex, race/ethnicity, annual family income, and body mass index.

Results

Adjusted linear regressions (p-values < 0.0001) showed that adolescents were more sedentary than children during school, afterschool, and weekday evening periods as well as all the weekend periods. However, during school (36.3 ± 7.3 vs. 28.2 ± 7.2 min/hour; b = -7.4 [-8.1, -6.6]) and afterschool periods (31.1 ± 7.7 vs. 22.7 ± 7.0 min/hour; b = -7.8 [-8.6, -7.0]) showed the largest weekly ST disparities by developmental stage. Overall, the during school and after school hours constitute most (during school = 35% and afterschool = 16%) of the weekly ST disparity between children and adolescents.

Conclusions

Our data provide interventionists with estimates of the potential for ST reduction in each setting and period of the day among US adolescents. Future research should gather information about the barriers and facilitators of ST in adolescents by period of the day to help understand factors driving disparities.