Better Objective Sleep Quality in Older Adults with High Subjective Memory Decline

Background: Sleep disturbance is implicated in memory function across normal aging and neurodegenerative disease. Furthermore, there is mounting evidence to suggest that high levels of subjective memory decline (SMD) may signal very early neurodegenerative changes associated with Alzheimer's disease (AD). This view prompts research examining the relationship between SMD and other risk factors for cognitive decline, including sleep disturbance. Objective: To determine whether objective and subjective indices of sleep predict SMD in older adults. Methods: 181 community-based older adults were divided into groups of high and low SMD based on their responses to the Memory Assessment Complaint Questionnaire (MAC-Q). They undertook two weeks of objective sleep monitoring (actigraphy), and completed a subjective sleep quality assessment using the Pittsburgh Sleep Quality Index. Results: Hierarchical logistic regression indicated that after controlling for demographics and mood, objective sleep quality predicted high SMD group status (Delta Nagelkerke R-2 = 0.07, chi(2) = 9.80 (3), p = 0.020), while subjective sleep quality did not. Contrary to expectation, however, less sleep disruption predicted high SMD. Conclusion: These unexpected results may suggest a non-linear trajectory between sleep and memory decline in aging. The findings are discussed in relation to previous research, which taken together, may indicate compensatory sleep patterns of reduced sleep disruption in people with high levels of SMD. These preliminary findings suggest the utility of including analysis of sleep behavior in further longitudinal research of this at-risk group of older people.