Association of changes in sleep duration and quality with incidence of depression: A cohort study.

BACKGROUND: The longitudinal relationship between sleep duration, sleep quality, and their changes with the risk of depressive symptoms is unclear. We examined the association between sleep duration, sleep quality, and their changes with incident depressive symptoms. METHODS: A total of 225,915 Korean adults without depression at baseline with a mean age of 38.5 years were followed for an average of 4.0 years. Sleep duration and quality were assessed using the Pittsburgh Sleep Quality Index. The presence of depressive symptoms was assessed using the Center for Epidemiologic Studies Depression scale. Flexible parametric proportional hazard models were used to determine hazard ratios (HRs) and 95 % confidence intervals (CIs). RESULTS: In total, 30,104 participants with incident depressive symptoms were identified. Multivariable-adjusted HRs (95 % CIs) for incident depression comparing sleep durations of ≤5, 6, 8, and ≥9 h with 7 h were 1.15 (1.11-1.20), 1.06 (1.03-1.09), 0.99 (0.95-1.03), and 1.06 (0.98-1.14), respectively. A similar trend was observed in patients with poor sleep quality. Compared with participants with persistently good sleep quality, participants with persistently poor sleep quality or who developed poor sleep quality were associated with the risk of incident depressive symptoms [HRs (95 % CIs) of 2.13 (2.01-2.25) and 1.67 (1.58-1.77), respectively]. LIMITATIONS: Sleep duration was assessed using self-reported questionnaire and the study population may not reflect general population. CONCLUSIONS: Sleep duration, sleep quality and their changes were independently associated with incident depressive symptoms in young adults, suggesting that inadequate sleep quantity and quality play a role in depression risk.