The triangular relationship of physical activity, depression, and inflammatory markers: A large cross-sectional analysis with NHANES data

Depression is a major public health problem worldwide and is closely related with systemic inflammatory responses. Additionly, physical activity (PA) is thought to be associated with lower levels of depression and inflammatory markers. This study aimed to elucidate the complex interactions between PA, depression, and inflammatory markers. Based on the National Health and Nutrition Examination Survey (NHANES), various logistic regression were applied to analyze the pairwise correlations among the three. Restrictive cubic splines were constructed to explore the nonlinear relationship between PA and depression. Mediation models were used to identify the mediating role of inflammatory markers. The findings revealed a positive link between depression and inflammatory marker, whereas PA was inversely correlated with both inflammatory marker and depression. Particularly, we noticed the greatest reduction in the risk of depression when the level of PA was between 1200 and 1722 MET-min/week. Besides, we demonstrated that inflammatory markers mediate the potential effects of physical inactivity on depression, ranging from 1.72 % to 6.25 %. In conclusion, PA appear to protect against depression, in which inflammatory markers may play a mediating role. Moreover, we determined the optimal dosage of PA to minimize the likelihood of depression, thereby offering valuable guidance for managing depression.