Disrupted sleep and risk of depression in later life: A prospective cohort study with extended follow up and a systematic review and meta-analysis

Background: Sleep difficulties increase the risk of current and future depression, but it is unclear if this relationship is causal. Methods: Prospective cohort study of a community sample of men aged 70–89 years followed for up to 17 years. Initial assessments occurred between 2001 and 2004. Participants were followed until death or 31 December 2018. Patient Health Questionnaire (PHQ-9) ≥ 10 at subsequent waves of assessments (every 2–3 years) or the recorded diagnosis of a depressive disorder in the Western Australian Data Linkage System marked the onset of depression during follow up. We excluded from follow up men with prevalent depression. The systematic review of longitudinal studies examining the association between disrupted sleep and depression in later life followed PRISMA guidelines. Results: 3441 of 5547 older men reported sleep difficulties at study entry. Current or past depression affected 437 of 5547 participants. Of the 4561 older men free of depression, 2693 reported sleep difficulties. The hazard ratio (HR) of incident depression among participants with sleep problems was 1.67 (95%CI = 1.39–2.00). Statistical adjustments for age, place of birth, education, smoking and physical frailty did not change the effect-size of this association. The systematic review identified another 14 studies, and the meta-analysis yielded an overall risk ratio of depression of 1.82 (95%CI = 1.69–1.97), although the overall quality of available evidence was sub-optimal. Conclusions: Disrupted sleep increases the risk of depression in later life and this seems unlikely to be due to reverse causality. Older adults with sleep difficulties are legitimate targets of interventions to prevent depression