The association of physical activity, sleep, and screen time with mental health in Canadian adolescents during the COVID-19 pandemic: A longitudinal isotemporal substitution analysis.

Background: The impact of COVID-19 on adolescent mental health is a global concern. Increased screen time and reduced physical activity due to the lockdown measures have been linked to detrimental mental health outcomes; however, the literature remains limited by cross-sectional and retrospective designs, and consideration of behaviours in isolation. Prospective evidence is necessary to examine whether moderate-to-vigorous physical activity (MVPA), sleep and screen time influenced changes in mental health. Method: Analyses used data from a prospective cohort study of secondary school students in Canada with baseline data from the 2018-2019 school year and linked follow-up data from online surveys completed during the initial COVID-19 outbreak (May-July 2020). Multilevel linear regression models were used to evaluate the within- and between-person isotemporal substitution effects of sleep, MVPA and screen time behaviours on depression, anxiety, subjective well-being, and trait emotional dysregulation. Results: Linked longitudinal data from 2645 students attending 44 schools were available. Between-person effects indicated that individuals who engaged in more MVPA and sleep while minimizing screen time had lower depression scores, less severe emotional dysregulation, and better subjective well-being. While controlling for between-person effects, within-person year-on-year change suggests those who increased screen time while decreasing either MVPA or sleep experienced mental health decline on all outcomes. Conclusion: MVPA and sleep were associated with youth mental health during the early COVID-19 lockdown. Increasing MVPA and sleep (or at least mitigating the increase of screen time) compared to the prior year was associated with better mental health during the early pandemic. A limitation to consider is that the screen time measure represents a combination of screen behaviours, and effects of replacing screen time may have varied if distinctions were made.

Changes in Canadian Adolescent Time Use and Movement Guidelines During the Early COVID-19 Outbreak: A Longitudinal Prospective Natural Experiment Design.

BACKGROUND: Comprehensive, prospective, longitudinal data are lacking on the effects of the COVID-19 outbreak on adolescents' movement behaviors (moderate to vigorous physical activity [MVPA], sleep, recreational screen use, and strengthening exercises). The purpose was to compare movement behavior changes among adolescents affected by the pandemic with controls. METHODS: Survey data from 10,659 students at 82 Canadian secondary schools (aged 12-19 y) during the 2018-2019 and 2019-2020 school years were analyzed. One-year change in time spent in movement behaviors and likelihood of meeting Canadian 24-hour movement guidelines was compared between preoutbreak controls (October 2019-March 2020) and early outbreak respondents (May-July 2020) after controlling for sociodemographic factors. RESULTS: Compared with controls, the early outbreak group reported a greater decrease in time spent in MVPA and greater increases in time spent in sleep and recreational screen use. The early outbreak group was less likely to meet MVPA and recreational screen time guidelines but more likely to meet guidelines for strengthening exercises and sleep duration. CONCLUSIONS: Findings for MVPA and screen time changes were in the same direction as retrospective reports from children and youth samples. Sleep adherence may have improved due to no longer having to commute to school. Strengthening exercises may represent physical activity that is easier to do in the home with minimal equipment leading to improved adherence during restrictions.