Abstract
STUDY OBJECTIVES: Insomnia may be a modifiable risk factor for later-life cognitive impairment. We investigated: (1) which insomnia symptoms are associated with subsequent cognitive functioning across domains; (2) whether insomnia-cognition associations are mediated by mental and physical health; and (3) whether these associations are modified by gender. METHODS: Participants included 2595 adults ages 51-88 at baseline (Mage=64.00 ± 6.66, 64.5% women) in the Health and Retirement Study. The frequency of insomnia symptoms (difficulty initiating sleep, night time awakenings, early awakenings, and feeling unrested upon awakening) at baseline (2002) were quantified using a modified Jenkins Sleep Questionnaire. Cognition was assessed in 2016 via the Harmonized Cognitive Assessment Protocol and operationalized with factor scores corresponding to five domains. Depressive symptoms and vascular conditions in 2014 were assessed via self-report. Structural equation models estimated total, indirect, and direct effects of insomnia symptoms on subsequent cognition through depressive symptoms and vascular diseases, controlling for baseline sociodemographic and global cognition. RESULTS: Frequent difficulty initiating sleep was associated with poorer episodic memory, executive function, language, visuoconstruction, and processing speed 14 years later (-0.06 ≤ β ≤ -0.04; equivalent to 2.2-3.4 years of aging). Depressive symptoms explained 12.3%-19.5% of these associations and vascular disease explained 6.3%-14.6% of non-memory associations. No other insomnia symptoms were associated with cognition, and no associations were modified by gender. CONCLUSIONS: Difficulty initiating sleep in later life may predict future cognitive impairment through multiple pathways. Future research with longitudinal assessments of insomnia, insomnia treatments, and cognition is needed to evaluate insomnia as a potential intervention target to optimize cognitive aging.