The joint and interaction associations of physical activity and sleep with depression: a cohort study

Despite substantial evidence regarding independent associations of physical activity and sleep quality with depression, their joint and interactive effects remain inadequately characterized. This study aimed to investigate the independent, joint, and interactive associations of physical activity and sleep quality with incident depression in a large prospective cohort.

This prospective cohort study included 323,910 depression-free UK Biobank participants recruited between 2006 and 2010, with a median follow-up of 13.44 years. Physical activity was assessed using the International Physical Activity Questionnaire-Short Form, measuring total (TPA), moderate (MPA), and vigorous physical activity (VPA). Sleep quality was evaluated using six traits to construct a comprehensive score (0-6). Incident depression was ascertained through ICD-10 codes from linked health records. Cox proportional hazards regression models explored the independent, joint, and interactive associations of physical activity and sleep quality with depression risk.

During follow-up, 16,983 (5.24%) participants developed depression. Both physical activity and sleep quality demonstrated significant associations with depression. Participants with the lowest TPA tertile and poor sleep quality (HR: 3.802, 95% CI: 3.405-4.247) showed substantially higher depression risk than those with recommended TPA and high sleep quality. Compared with participants with recommended VPA (600-1200 MET-minutes/week) and high sleep quality, those with VPA < 600 MET-minutes/week (HR: 3.626, 95% CI: 3.137-4.190) or VPA > 1200 MET-minutes/week (HR: 3.338, 95% CI: 2.856-3.901) combined with low sleep quality had markedly elevated depression risk. Physical activity's protective associations were substantially attenuated in poor sleep contexts, whereas poor sleep's adverse effects persisted across all physical activity levels. A modest but statistically significant additive interaction was observed specifically between VPA and sleep quality (P < 0.05), while no significant interactions were detected for TPA or MPA. Multiplicative interactions were not statistically significant for any physical activity measure.

There were independent and joint associations of physical activity and sleep quality with incident depression, with a modest additive interaction observed specifically for vigorous physical activity and sleep quality. Physical activity's protective associations are attenuated in the context of poor sleep, while sleep quality's adverse associations persists across all activity levels.