0715 NREMembrance of Things Past: Obstructive Sleep Apnea Impacts Sleep Neurophysiology and Memory Retention in Aging

Abstract Introduction Obstructive sleep apnea (OSA) is associated with sleep disturbances, memory impairment, and dementia risk in older adults. The impact of OSA on sleep neurophysiology and related memory function remains unclear. We examined associations among OSA severity, non-rapid eye movement (NREM) sleep expression, and overnight memory retention in cognitively intact older adults at risk for Alzheimer’s disease (AD). Methods Overnight clinical polysomnography (PSG) with 256-channel electroencephalography (EEG) was conducted in 81 cognitively intact older adults (aged 61.68◻5.99 years, 49 female, Apnea/hypopnea Index, AHI: 7.61◻10.64 ), with word-pairs task (WPT) encoding and cued recall occurring prior to and following sleep. AHI, respiratory disturbance index (RDI), and oxygen desaturation index (ODI) were used as measures of OSA severity and cube-root transformed to normality. EEG data underwent preprocessing, artifact rejection, and segmentation into concatenated NREM epochs, and were then processed using multitaper spectral analysis with 11 tapers. Behavioral data, obtained as overnight proportion change in retention of word-pairs, were also cube-root transformed to enhance normality. Topographical correlations were then computed to examine associations between NREM sleep features and OSA severity, using 5000 permutations of threshold-free cluster enhancement (TFCE) for multiple comparisons correction. Multiple linear regression modeling was leveraged to examine whether spatiospectral NREM clusters associated with OSA severity were in turn predictive of overnight memory retention when adjusting for age and sex. Results Global, TFCE-significant (p< 0.05 corrected) negative correlations were seen between delta power (1-4.5Hz) and AHI and RDI, theta power (4.5-7.5Hz) and AHI and RDI, alpha power (7.5-11Hz) and RDI, and slow sigma power (11-13Hz) and ODI . Regression models (adjusted for age and sex) using cluster averages of spectral power from prior correlations to predict WPT performance further revealed significant effects for theta power (AHI cluster: B=0.077, p=0.007; RDI cluster: B=0.076, p=0.008), alpha power (RDI cluster: B=0.107, p=0.010), and for slow sigma power (ODI cluster: B=0.203, p=0.007), but not for delta power (both clusters: p>0.33). Conclusion These findings indicate that OSA is associated with globally disrupted NREM sleep expression, and that reduced theta, alpha, and spindle activity is further associated with impaired overnight episodic memory retention. Support (if any) NIH grants R56AG052698, P50AG033514, F31AG048732, K01AG068353.