The roles of physical activity and sedentary behavior in the relationship between socioeconomic status and depressive symptoms: Observations from a national study

Background: While the association between socioeconomic status (SES) and depression is well-documented, the relative contributions of physical activity (PA) and sedentary behavior (SB) to this association remain unclear. This study was to explore the effects of PA, SB in the associations between SES and depressive symptoms, respectively. Methods: Our study included 15,906 adults (age >= 20 years) from the National Health and Nutrition Examination Survey (NHANES), 2011-2020. A four-way decomposition was applied with PA and SB as mediators to explore the mediation and interaction effects between SES and depressive symptoms. Results: It was found that low SES was associated with greater risk of depressive symptoms (odds ratios 3.18, 95 % confidence interval 2.56 to 3.94), as well as insufficient moderate-to-vigorous recreational activities (MVRA) (1.45, 1.24 to 1.70) and prolonged SB (0.77, 0.67 to 0.90). MVRA also showed a significant mediation effect that accounted for 5.48 % of the total effect of SES on depressive symptoms. Meanwhile, the interaction between MVRA and SES was also significant, accounting for 28.25 % of the total effect. In the single measure of SES, only the interaction between employment status and MVRA was statistically significant and accounted for 39.41 % of the total effect. Limitation: This study had a cross-sectional design, thus limiting our capacity to draw conclusive causal relationships. Conclusion: People with low SES may be suffered from higher risk of depressive symptoms. However, our findings showed that sufficient MVRA (at least 150 min per week) could buffer against the risk of depressive symptoms, particularly for those who are unemployed.