Naturalistic Measurement of Sleep in Older Adults with Amnestic Mild Cognitive Impairment: Anxiety Symptoms Do Not Explain Sleep Disturbance

Background: Sleep disturbance is prevalent in Alzheimer’s disease (AD). In amnestic mild cognitive impairment (aMCI), the preclinical stage of AD, deterioration in sleep quality has also been reported. Consensus is lacking, however, regarding what aspects of sleep are characteristically affected, whether the setting of the sleep recordings impacts these findings, and whether anxiety may account for the differences. Objective: The current study aimed to address these knowledge gaps by obtaining comprehensive sleep measurement in aMCI within a naturalistic environment using in-home sleep recordings. Methods: 17 healthy older adults and twelve participants with aMCI wore an actiwatch for two weeks to objectively record habitual sleeping patterns and completed two nights of in-home polysomnography. Results: In aMCI, habitual sleep disturbances were evident on actigraphy including greater wake after sleep onset (p = .012, d = 0.99), fragmentation (p = .010, d = 1.03), and time in bed (p = .046, d = .76). Although not statistically significant, there was a large group effect on polysomnography with aMCI demonstrating less slow-wave-sleep than controls (p >.05, d = .0.83). Anxiety did not mediate the relationship between the group and sleep in this small study. Conclusions: The results indicate that people with aMCI have poorer quality sleep than healthy controls, as indicated by greater sleep disruption and less slow-wave sleep, even in naturalistic settings. Additionally, anxiety symptoms do not mediate the relationship. Therefore, this research supports the view that sleep disturbance is likely to be indicative of neuropathological changes in aMCI rather than being attributed to psychological factors.