P051 SLEEP SPINDLES AND SWA DIFFERENTIALLY CORRELATE WITH OVERNIGHT EPISODIC AND VISUOSPATIAL MEMORY CONSOLIDATION IN OLDER ADULTS WITH AND WITHOUT MILD COGNITIVE IMPAIRMENT

INTRODUCTION: Sleep microarchitecture disruption is a feature of ageing that is further altered in neurodegenerative disorders. Sleep-memory links in younger adults have been established, however mechanistic pathways of this uncoupling in ageing is poorly understood. METHOD: Our sample consisted of n=46 mild cognitively impaired (MCI) older adults and n=32 cognitively-intact controls who underwent overnight polysomnography and episodic (Rey Auditory Verbal Learning test) and visuospatial (Rey-Osterrieth Complex Figure task) memory tasks that were administered before and after sleep. We examined group differences in overnight memory % retention and associations with NREM slow oscillations (SO, 0.25–1 Hz), delta power (0.5–4 Hz), N2 spindle events (occurrence [11–16 Hz] and slow [11–13 Hz] and fast [13–16 Hz] spindle density p/min) and REM theta power (4.5–8 Hz). RESULTS: Repeated measures ANCOVA, controlling for age, indicated greater memory scores in Controls compared to MCI on the episodic task, F=6.7 (p=.01), and no group differences in the visuospatial task (F=1.8, p=.17). In Controls, greater delta power was associated with increased episodic memory retention (r=.515, p=.006). In the MCI group, episodic memory was associated with fast spindle density (r=-.352, p=.04), and visuospatial memory was also associated with fast spindle density (r=-.385, p=.01) and spindle occurrence (r=-.479, p=.003). CONCLUSION: Sleep spindles appear to be negatively associated with memory retention, specifically in MCI. However, given the heterogeneity of MCI, further analysis of its cognitive subtypes is warranted. Comprehensive cognitive and neural pathophysiology profiling are required to better delineate the function of spindles in ageing.