0670 Respiratory Event-Related Hypoxemia, Electroencephalographic Response and Subjective Sleepiness in OSA

Abstract Introduction Standard metrics of obstructive sleep apnea (OSA) severity, such as apnea-hypopnea index (AHI), do not correlate well with daytime sleepiness. In OSA patients, there is considerable variability in the severity of hypoxemia and the electroencephalographic (EEG) response associated with respiratory events. We hypothesized that nocturnal hypoxemia and EEG responses would be associated with subjective daytime sleepiness in patients with moderate-to-severe OSA. Methods We used cross-sectional data from participants enrolled in a Canadian Sleep and Circadian Network’s clinical cohort of patients with suspected OSA who had moderate-to-severe OSA (AHI>15/hr). Event-related hypoxemia was quantified as the mean event-related hypoxic burden (HBev): mean area under the oxygen desaturation curve. EEG responses to respiratory events were quantified by calculating the power ratio (log(mean absolute power 6s after / mean absolute power 6s before the event)) across EEG frequency bands; subject-specific responses were defined as the mean EEG response across all events. We calculated an overall Brain Response to Events (BReTE) metric by summing power ratios across all frequency bands. Subjective daytime sleepiness was assessed by the Epworth Sleep Scale (ESS) with an ESS>10 considered indicative of daytime sleepiness). Logistic regression, controlling for age, body mass index, race, sex, AHI and comorbidities was employed to investigate hypothesized associations. Results We studied 468 patients (40%female) with a median [IQR] age=56 years [46,63], AHI=43events/hr [23,87], HBev=1.87%min [1.24,2.69]. More severe hypoxemia and a lower EEG response were independently associated with higher odds of daytime sleepiness. One standard deviation (SD) increase in HBev was associated with 41% higher odds of daytime sleepiness (95% CI: 1.14-1.75,p< 0.01), while a one SD increase in BReTE was associated with 27% lower odds of daytime sleepiness (95%CI: 0.58-0.91,p< 0.01). Blunted EEG responses were more prevalent across beta and gamma EEG frequencies. AHI was not associated with daytime sleepiness. Conclusion Greater event-related hypoxemia and blunted EEG responses were independently associated with subjective daytime sleepiness in moderate-to-severe OSA, emphasizing the pivotal roles of hypoxemia and EEG in evaluating daytime sleepiness in OSA. EEG findings could be the result of adaptations to chronic OSA exposure, resulting in reduced arousal responses. Future prospective studies should explore these intricate associations further. Support (if any)

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