Physical Activity As a Mediator Between Depressions and Sleep Disorders

Background/Purpose: The purpose of this paper was to investigate whether time spent by adults in moderate to vigorous physical activity (MVPA) mediates the relationship between depression and sleep disorders.

Method: Data from the 2005-2006 US National Health and Nutrition Examination Survey for 3,174 adults (49% male) over the age of 18 was analyzed. Depression-related and sleep disorder-related parameters were extracted from corresponding questionnaires.  Each participant’s MVPA time per day were calculated based on ActiGraph accelerometers’ intensity counts. Multiple regression analyses were conducted to assess each component of the proposed mediation model. 

Analysis/Results: Depression was positively associated with sleep disorders (B = .484, t(3172) = 31.14, R² = .234, p = 0.000). There was also a negative-relationship trend between MVPA time and depressions (B = -.092, t(3172) = -5.18, R² = .008, p = 0.000), as well as sleep disorders (B = -.122, t(3172) = -6.92, R² = .015, p = 0.000). In this study, a 95% confidence interval of the indirect effects was obtained with 5000 bootstrap resamples. Results of the mediation analysis confirmed the partial mediator role of MVPA time in the relation between depression and sleep disorders (CI = .01 to .03) even the direct effect of depression on sleep disorders is still statistically significant (B = .477, t(3172) =30.670, R² = .240, p=0.000).

Conclusions: MVPA time in daily life was found to be a partial mediator between depressions and sleep disorders. For people who have depression, they might want to increase their MVPA time to decrease possible sleep disorder problems caused by their depression.