Effects of reallocating physical activity, sedentary behaviors, and sleep on mental health in adolescents

https://doi.org/10.1016/j.mhpa.2020.100380Get rights and content

Highlights

  • Mental health benefits differ based on sleep status.

  • Behaviors contribute differently to dimensions of mental health.

  • Beneficial outcomes of MVPA may be predicated on adolescents getting adequate sleep.

  • Replacing screen time with other behaviors is associated with better mental health.

  • Mental health benefits may be obtainable at intervals as short as 15 min.

Abstract

Objective

Physical activity, sedentary behavior, and sleep are associated with mental health in adolescents. Mental health may depend not only on the amount of time spent in a specific activity, but also on the activity it displaces. The aim of this study was to examine the impact of reallocating 15 min of time spent in one health behavior with 15 min in another on adolescent mental health.

Methods

Cross-sectional data from the students participating in the COMPASS Study (2018–2019) were analyzed (N = 46,413). Participants self-reported the amount of time they spent engaged in moderate-to-vigorous physical activity (MVPA), doing homework and using screens, and their sleep duration on average each day, depressive symptoms, anxiety, and flourishing. Data were analyzed using isotemporal substitution modeling.

Results

Among adolescents getting less than the recommended amount of sleep, replacing any behavior with sleep was generally associated with better mental health outcomes. Conversely, among adolescents getting adequate sleep, the findings did not support replacing other behaviors with sleep with the exception of screen time. Replacing homework and MVPA with sleep was associated with less flourishing regardless of sleep duration.

Conclusions

Replacing screen time with any behavior may be better for mental health outcomes. Results provide further support for the critical role of sleep in promoting healthy development during adolescence, though more sleep than is recommended may confer little benefit for mental health. The findings demonstrate that mental health benefits may be obtainable at intervals as short as 15 min.

Section snippets

Procedure

This study used a sample of adolescents participating in the COMPASS (Cannabis, Obesity, Mental health, Physical activity, Alcohol, Smoking, Sedentary Behavior) study. COMPASS is a prospective cohort study (2012–2021) that collects data from full school samples of students in grades 9 through 12 attending participating secondary schools across Canada. A full description of the COMPASS host study methods is available in print (Leatherdale, Brown, et al., 2014) or online (www.compass.uwaterloo.ca

Data analysis

The distributions of the physical activity, screen time, homework, and sleep scores were examined. Based on the observed distributions of responses, students with missing data as well as unrealistic or outlier responses were removed. Sample characteristics were calculated and linear mixed models with random intercept were used to examine the impact of changes in MVPA, sleep, homework, and screen time on anxiety, depression and flourishing scores. All models controlled for sex, province, grade,

Results

Students with missing values on mental health scales (n = 3679) and covariates (n = 2042) were removed. Using outlier criteria of three standard deviations from the mean, students who indicated average daily MVPA (n = 293) or homework time (n = 174) greater than 6 h or sleep time (n = 2969) less than 3 h were removed, as were students who indicated a total activity time (including physical activity, screen time, homework, and sleep) of more than 24 h (n = 5040), resulting in a final analytic

Discussion

This study investigated how displacing 15 min of MVPA, sedentary behavior, or sleep with equivalent time in another behavior was associated with mental health outcomes in adolescents using isotemporal substitution modelling. There was evidence of non-linear associations between sleep and mental health, consistent with previous research (Zhang et al., 2017). Consequently, all findings were stratified across sleep duration. While similarities emerged between those meeting sleep guidelines and

Conclusion

There is a wealth of support for increasing MVPA, reducing sedentary time, and getting adequate sleep to promote positive mental health outcomes among adolescents (Biddle et al., 2019; Hoare et al., 2016; Zhang et al., 2017). However, due to the finite time available to engage in these behaviors and engaging in one behavior necessarily means displacing time spent in another, the effects of replacing one health behavior with another on mental health is of interest. Taken together, our findings

Declaration of competing interest

Editorial Disclosure:

In his role as Founding Editor, Guy Faulkner had no involvement in the peer-review of this article and had no access to information regarding its peer-review. Full responsibility for the editorial process for this article was delegated to Adrian Taylor.

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    This research was supported by the Social Sciences and Humanities Research Council of Canada through a postdoctoral fellowship awarded to JG. The COMPASS study has been supported by a bridge grant from the CIHR Institute of Nutrition, Metabolism and Diabetes (INMD) through the “Obesity – Interventions to Prevent or Treat” priority funding awards (OOP-110788; awarded to SL), an operating grant from the CIHR Institute of Population and Public Health (IPPH) (MOP-114875; awarded to SL), a CIHR project grant (PJT-148562; awarded to SL), a CIHR bridge grant (PJT-149092; awarded to KP/SL), a CIHR project grant (PJT-159693; awarded to KP), and by a research funding arrangement with Health Canada (#1617-HQ-000012; contract awarded to SL).

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