Subjective well-being mediates the longitudinal effect of insomnia symptoms on internalizing symptoms in community-dwelling older adults

Objectives The associations among insomnia symptoms and internalizing symptoms are well-established, particularly in older adults; however, the mediating factors remain inconsistent. This study seeks to explore the longitudinal relationship between insomnia symptoms and internalizing symptoms in older adults, exploring subjective well-being as a potential mechanism. Methods This study used a longitudinal design and was implemented from May to September 2023, involving 315 Chinese community-dwelling older adults aged 60 + (Mean age = 71.2, SD = 6.8 years; 62.9% female). Insomnia symptoms, internalizing symptoms, and subjective well-being data occurred at three measurement points, spaced 45 days apart. Cross-lagged panel models (CLPM) were utilized to assess the longitudinal and bidirectional associations, along with mediation effects. Results CLPM results indicated that insomnia symptoms at baseline significantly predicted internalizing symptoms at both the second and third measurement points, while internalizing symptoms did not predict subsequent insomnia symptoms. Longitudinal mediation analysis revealed that baseline insomnia symptoms predicted internalizing symptoms at the third measurement through subjective well-being at the second measurement, with significant indirect effects (β = -0.051, p = 0.018). No evidence was found for the reverse mediation effect of internalizing symptoms on insomnia symptoms via subjective well-being. Discussion This study demonstrates that insomnia symptoms exert a longitudinal influence on subsequent internalizing symptoms, but not the opposite, and subjective well-being operates as a mediating variable. Subjective well-being is identified as a modifiable factor that could be strategically targeted to alleviate the adverse effects of insomnia symptoms on internalizing symptoms in older adults.