The role of anxiety and depression in the relationship between physical activity and sleep quality: A serial multiple mediation model

•Physical activity was associated with better sleep quality.•Anxiety acted as a mediator in the exercise-sleep linkage.•Likewise, depression acted as a mediator in the exercise-sleep linkage.•Physical activity affected sleep via anxiety and depression in a serial manner.•Better mental health advances exercise-based programs targeting sleep improvement. Physical inactivity exacerbates poorer sleep quality, but potential underlying mechanisms of this association remain unknown. The present study aims to disentangle the pathways linking psychical activity to sleep quality through the serial mediation effect of anxiety and depression in a Chinese population. Data analyzed were from Guangdong Sleep and Psychosomatic Health Survey, a cross-sectional population-based study with a representative sample of adult inhabitants aged 18-85 years living in Guangdong province, China. A total of 13,768 participants were included with the response rate of 80.4%. Singe and serial mediation analyses were conducted to examine whether anxiety and depression mediated the relationship between physical activity and sleep quality, independently and jointly. Both direct and indirect effects of physical activity on sleep quality were found. As predicted, anxiety and depression mediated the relationship between physical activity and sleep quality (B Anxiety = -0.17, 95% bootstrap CI: -0.20 to -0.15; B Depression= -0.25, 95% bootstrap CI: -0.28 to -0.21), respectively. In addition, serial mediation analyses indicated that the association of physical activity and sleep quality is mediated by anxiety and depression in a sequential manner (B = -0.13, 95% bootstrap CI: -0.15 to -0.11). The primary limitation of the study is the cross-sectional design, which limits the causal inference ability. These findings highlight the role of anxiety and depression as serial mediators of the relationship between physical activity and sleep quality. Thus, exercise-based programs focusing on improving sleep could benefit from a multi-faceted approach therapeutically targeting psychiatric disorders.