Bidirectional associations between insomnia symptoms and depression: a prospective cohort study

Purpose: Depression and insomnia are both prevalent in older adults and exhibit a bidirectional relationship. Difficulty initiating sleep (DIS) and difficulty maintaining sleep (DMS) are major symptoms of insomnia. However, whether and how these two insomnia symptoms differ in their associations with depression among older adults is unknown. We aimed to investigate the association between insomnia symptoms (DIS and DMS) and depressive symptoms among older adults. Methods: We used data of the 3,377 community-dwelling older adults from five waves (2011–2015) of the National Health and Aging Trends Study, a nationally representative survey of Medicare Beneficiaries in the United States. Depressive symptoms were assessed by the Patient Health Questionnaire-2. Insomnia symptoms included self-reports of DIS and DMS. Generalized estimating equation models were used to examine the concurrent and lagged associations between insomnia symptoms and depressive symptoms. Results: Participants were on average 76.0 ± 7.1 years old, predominantly female (59.2%), and non-Hispanic white (72.1%). Both DIS and DMS were concurrently associated with depressive symptoms. Longitudinally, DIS predicted subsequent depressive symptoms even after full adjustment, whereas DMS did not. Conversely, depressive symptoms were concurrently associated with both DIS and DMS, but only predicted subsequent DIS, not DMS. Conclusions: These findings underscore the bidirectional yet distinct relationships between specific insomnia symptoms and depression in older adults. DIS shows consistent bidirectional associations with depressive symptoms, while DMS is only concurrently associated. Understanding the specific interplay between these conditions may enable the development of more targeted and effective prevention and treatment strategies. Clinical trial number: Not applicable.