How are insomnia symptom subtypes associated with the risk of depressive symptoms among elders: Evidence from a...

This study aims to characterize the generalizable associations between insomnia symptom subtypes and the risk of depressive symptoms, providing a basis for the prevention and control of insomnia-related depressive symptoms in countries/regions lacking relevant evidence.

We analyzed 50,593 older adults from four cohorts in India, America, Mexico, and Europe (2017-2019). Depressive symptoms were assessed using cohort-specific scales, and insomnia symptom subtypes, including difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), early morning awakening (EMA), and nonrestorative sleep (NRS), were measured with the Jenkins Sleep Scale. Associations between insomnia symptom subtypes and depressive symptoms were estimated using multiple logistic regressions, and meta-analysis was applied to obtain pooled effects while excluding regional heterogeneity. Interactions between insomnia symptom subtypes and effect modifiers were examined, and the linear trend between the number of insomnia subtypes and depressive symptom risk was tested using the Mann-Kendall test.

The average ORs for depressive symptoms were 1.64 (95 % CI: 1.19-2.27) for DIS, 1.33 (95 % CI: 1.18-1.51) for DMS, 1.54 (95 % CI: 1.36-1.73) for EMA, and 1.94 (95 % CI: 1.65-2.28) for NRS. Sex and health status modified these associations. In Mexico, DMS and EMA had a synergistic effect. The number of insomnia symptom subtypes is approximately linearly associated with depressive symptom risk.

All four insomnia symptom subtypes increased the risk of depressive symptoms in older adults, with variation across countries and subgroups. These findings highlight the importance of tailored prevention strategies targeting high-risk populations to reduce the burden of insomnia-related depressive symptoms.