0744 Metrics of Sleep Apnea Severity and Sleep-Dependent Memory Consolidation

Abstract Introduction Obstructive sleep apnea (OSA) is common in older adults and has recently been implicated in the pathogenesis of Alzheimer’s disease (AD). Sleep disruption is a possible reversible cause of memory impairment. Furthermore, quality of sleep has been determined to be one of the most important variables affecting overnight memory consolidation. As part of a larger study, data are presented evaluating correlations between markers of sleep apnea severity and sleep-dependent memory consolidation. Methods Seventy-one older adults ages 65-83 (M=70, SD=4.1) with normal cognition underwent polysomnography (PSG) and completed sleep questionnaires as part of a larger study. The sample was 54.9% women, 83.1% White, and 91.5% Non-Hispanic. Severity of sleep apnea was assessed using several metrics: Daytime sleepiness measured by the Epworth Sleepiness Scale (ESS), apnea-hypopnea index (AHI) based on American Academy of Sleep Medicine recommended, Total Sleep Time with Oxygen Saturation below 90% (T90), the lowest level of oxygen saturation reached during sleep (SPO2 Nadir), and hypoxic burden. Sleep-dependent memory consolidation was assessed using the Word-pairs Association (WPA) task, which shows semantically related word pairs for 5 seconds for the participant to learn, and the next morning, post-sleep, the delayed recognition test is performed. Results Descriptive analyses showed a median daytime sleepiness of 7 (SD=3.1), AHI of 28 (SD=24.3), and body mass index of 27 (SD=7.1). Nonparametric correlations were performed to assess markers of sleep apnea severity as correlates of sleep-dependent memory consolidation. There were no significant associations between objective measures of OSA severity, particularly AHI, hypoxic burden, T90, and SPO2 Nadir. However, there was a significant negative association between subjective daytime sleepiness (ESS) and sleep-dependent memory consolidation (r=-0.30, p=0.01). Conclusion This study provides preliminary insights into the association between daytime sleepiness and sleep-dependent memory consolidation. The observed finding that lower daytime sleepiness is related to better sleep-dependent memory consolidation warrants further investigation into the underlying mechanisms and to assess whether alternate cognitive measures may be associated with objective severity metrics. Future research should assess relations with psychological factors, such as mood and coping, as these factors can impact memory and are not captured by PSG. Support (if any) 1R01AG063925-01A1 and T32MH018399