Accelerometer-derived movement behaviours and risk of mortality among individuals with pre-existing depression: prospective cohort study.

Background: Evidence is largely limited regarding the extent to which abnormal behavioural profiles, including physical inactivity, sedentary behaviour and inadequate sleep duration, impact long-term health conditions in individuals with pre-existing depression.

Aims: To investigate the associations between accelerometer-derived daily movement behaviours and mortality in individuals with pre-existing depression.

Method: Between 2013 and 2015, a total of 10 914 individuals with pre-existing depression were identified from the UK Biobank through multiple sources including self-reported symptoms, records of antidepressant usage and diagnostic recording based on the 10th Revision of the International Classification of Diseases (ICD-10) codes F32-F33. These participants were subsequently followed up until 2021. Wrist-worn accelerometers were used for objective measurement of sleep duration, sedentary behaviour, moderate-to-vigorous physical activity (MVPA) and light physical activity (LPA) over a span of seven consecutive days.

Results: During a median follow-up of 6.9 years, 434 deaths occurred among individuals with pre-existing depression. We observed a U-shaped association between sleep duration and mortality in individuals with pre-existing depression, with the lowest risk occurring at approximately 9 h/day. Both MVPA and LPA exhibited an L-shaped pattern in relation to mortality, indicating that engaging in higher levels of physical activity was associated with lower risk of mortality in individuals with pre-existing depression, but the beneficial effect reached a plateau after 50 min/day for MVPA and 350 min/day for LPA. We found a positive association between sedentary time and mortality, and the risk apparently increased above 8 h/day. Moreover, substituting 1 hour/day of sedentary time with LPA or MVPA was significantly associated with a 12% (hazard ratio: 0.88, 95% CI: 0.83-0.94) and 24% (hazard ratio: 0.76, 95% CI: 0.61-0.94) lower risk of mortality, respectively.

Conclusions: Our study found the beneficial effect of adequate sleep duration, high levels of physical activity and short sedentary time on risk of mortality among individuals with pre-existing depression.