Association between device-based measured physical activity timing and depression risk: a prospective cohort study of UK Biobank participants

Abstract

Introduction Physical activity (PA) decreases the risk of mental diseases. Although PA timing has been hypothesised to affect mental health outcomes, no large-scale epidemiological cohort studies have been performed. We investigated the association between PA timing and incident depression in the general population.Methods A total of 89 934 European participants (62.4 +/- 7.9 years, age range: 43-79 years, 44.8% men) without a history of depression were analysed. Hourly PA levels were derived from accelerometry data and standardised for the total daily amount of PA. Participants were followed for a maximum of 8.5 years. Risks of incident depression dependent on individually standardised hourly PA level were assessed using Cox proportional-hazards models adjusted for potential confounders.Results During follow-up, 1748 participants developed depression. Using the hourly standardised PA levels, we observed higher risks for incident depression with higher night-time PA (eg, at 4:00 HR 1.35; 95% CI 1.28, 1.41), and lower depression risks with higher morning-time PA (eg, at 9:00 HR 0.85; 95% CI 0.81, 0.89). Also in the subgroup analysis, compared with participants who were most active during midday, participants with most PA in the early morning had a lower risk for incident depression (HR 0.80; 95% CI 0.68, 0.95). No differences were observed when analyses were stratified for sex, chronotype or for the overall objective PA level.Conclusions Morning PA was associated with lower risk and night-time PA was associated with increased risk of depression. These findings may suggest that future intervention studies should include timing as an additional dimension of PA as a possible treatment and prevention strategy for depression.