Impact of cardiovascular risk factors on associations between state and trait indices of major depression disorder and objectively assessed physical activity, sleep and circadian rhythmicity within a population based cohort.

BACKGROUND

Few studies of the association between accelerometry-assessed physical activity with major depressive disorder (MDD) have considered the influence of both the averages and variability of all three domains of the 24 hour activity cycle including sleep, physical activity, and circadian rhythmicity, the physical health correlates of depression, and the extent to which changes in sleep and physical activity reflect current state versus enduring patterns of MDD in people with depression.

METHODS

The sample includes 2307 participants from a population cohort from Lausanne, Switzerland. Average and variability of daily sleep (SL), physical activity (PA), and circadian rhythmicity (CR) were derived from accelerometry.

RESULTS

Cardiovascular risk factors, particularly cigarette smoking and body mass index (BMI), were significantly associated with both the average and variability of sleep, phyiscal activity and circadian rhythmicity, and with MDD. Lower average and less variable physical activity, as well as more variable circadian rhythmicity were associated with remitted MDD, whereas later sleep midpoint and greater variation of sleep duration variability were associated with depressive states.

LIMITATION: The single geographic setting, cross-sectional nature and two-week assessment period may limit the generalizability of these findings.

CONCLUSION

These results demonstrate the importance of considering both the average and variability of accelerometry-derived phenotypes that may distinguish state from trait manifestations of MDD. Further, the confounding influence of smoking, particularly on state manifestations of MDD, should be considered in studies of accelerometer derived phenotypes, particularly sleep characteristics. Interventions for depression should therefore consider modification of health behaviors such as smoking and overweight, as well as stabilizing the 24-hour rest-activity cycle, rather than treatments that focus solely on the average levels of mood, sleep or physical activity alone.