The Relationship Between Sleep Disturbances and Episodic Memory in Older Adults.

Abstract

Impaired episodic memory in older adults has been posited to be related to sleep disturbances which are revealed by self-reported questionnaires and objective devices but the relationship between these two measured results is unclear. Sleep disturbances have been tied to declines in attention, executive function, and cognitive reserve, which may contribute to impaired episodic memory. However, how sleep disturbances relate to these cognitive functions and in turn influence episodic memory remains unclear. Age and depressive symptoms are correlated with sleep disturbances and episodic memory decline in older adults; however, the role of age and depressive symptoms in explaining the relationship between sleep disturbances and episodic memory remains unclear The specific aims were (a) to determine the conceptual structure of sleep disturbances in older adults; and (b) to determine the relationship between sleep disturbances and episodic memory in older adults, including the roles of attention, executive function, cognitive reserve, depressive symptoms, and aging in the relationship. This descriptive study included a convenience sample of (N=62) older adults (age 60-88). Two sleep questionnaires and actigraphy were used to measure sleep; the Hopkins Verbal Learning Test-Revised was used to assess episodic memory; the CogState computerized battery was used to evaluate attention and executive function; and the Wide Range Achievement Test 4-Reading subtest was used to measure cognitive reserve. Descriptive statistics, Pearson’s correlation, exploratory factor analysis, and hierarchical multiple regression analyses were conducted to analyze data. Self-reported sleep disturbances significantly correlated with objective sleep time and wakefulness during sleep periods, but this relationship was only substantial for objective sleep time. In older adults, more objective difficulty in falling and staying asleep, better executive function, more cognitive reserve and unexpectedly, higher level of daytime sleepiness explained better episodic memory after controlling for the covariates. The influence of sleep disturbances on episodic memory was stronger among those participants with more, as compared to less depressive symptoms. The study results suggest some possible directions to develop sleep interventions to prevent episodic memory declines in older adults. Future studies may focus on improving daytime sleepiness and difficulty in falling and staying asleep to prevent episodic memory declines.