A time compositional analysis of the association between movement behaviors and indicators of mental health in young adults.

Background: Movement behaviors (i.e., physical activity [PA], sedentary behaviors [SB], sleep) relate to mental health. Although movement behaviors are often analyzed as distinct entities, they are in fact highly inter-dependent (e.g., if an individual increases sleep, then PA and/or SB must be reduced) and these dependencies should be accounted for in the analysis. We tested whether perceptions of time spent in movement behaviors (i.e., moderate-to-vigorous intensity PA [MVPA], light physical activity [LPA], SB, and sleep) related to depressive symptoms and self-report mental health in young adults using a compositional analysis. We then estimated change in depressive symptoms with reallocation of time across movement behaviors using compositional time-reallocation models.

Methods: Data were drawn from the longitudinal NDIT dataset. Complete data were available for 770 young adults (M  = 20.3, 55% females).

Results: The proportion of time spent in MVPA relative to other movement behaviors related to depressive symptoms non-significantly and to mental health significantly. Reallocating 15 min from MVPA to SB resulted in a significant (0.46 unit) increase in depressive symptoms, and reallocating 15 min of MVPA to LPA was associated with a (0.57) increase in depressive symptoms.

Conclusion: These results indicate the importance of relative time spent in each movement behavior to mental health. Further research should examine these associations over time.