The bidirectional relationship between sleep duration and depression in community-dwelling middle-aged and elderly individuals: evidence from a longitudinal study

Background: There are several studies that have focused on the relationship between sleep duration and depression, however, only a few prospective studies have centered on the bidirectional relationship between them. This four-year longitudinal study aimed to identify the association between sleep duration and depression in community-dwelling mid-age and elderly individuals. Methods: 10,704 participants from the China Health and Retirement Longitudinal Study (CHARLS) were included for baseline and four-year follow up. Of these individuals, 7866 and 2956 were used to identify the effects of sleep duration on onset and recurrent depression respectively. 4504 individuals with normal sleep duration at baseline were included to examine the effects of depression on changes of sleep time. The 10-item version of the Centre for Epidemiological Studies Depression scale (CESD-10) was used to access depressive symptoms, as well sleep duration was self-reported. Results: Participants with short sleep duration (<5 and 5-6 h) had a higher risk of depression onset (OR 1.69 [1.36-2.11], 1.48 [1.19-1.84]) and recurrent depression (OR 1.44 [1.12-1.86], 1.32 [1.00-1.74]) compared to participants with normal sleep durations (7-8 h). Long sleep durations (>9 h) had no significant risks for depression. Males and the elderly (over 60 years-old) were more sensitive to short sleep durations and experienced a higher incidence of depression. Individuals with depression were more likely to have short sleep durations instead of long ones (RRR 1.20 [1.02-1.43]). Conclusions: The present study identified the bidirectional relationship between sleep duration and depression. Short sleep durations were a risk factor for the onset and recurrent depression. Conversely, depression induced short sleep durations rather than excessive sleep durations. Future studies need to focus on identifying the mechanism between sleep duration and depression, and develop additional evidence-based cost-effective interventions to prevent depression and sleep problems. (c) 2018 Elsevier B.V. All rights reserved.