Differential associations of arousals and respiratory events on oxygen desaturation and resaturation parameters in sleep.

BACKGROUND: The severity of nocturnal blood oxygen saturation (SpO2) is associated with age, sex, and cardiorespiratory comorbidities. Frequency and timing of nocturnal arousals and respiratory events also display age, sex, and comorbidity-based differences. Hence, it is plausible that resaturation parameters may present an alternative avenue for the assessment of nocturnal arousals. METHODS: First visit data from the Sleep Heart Health Study was utilised to derive SpO2 parameters from 5804 participants. Participants missing SpO2 parameters, or with no desaturation events were excluded from final analysis. Manually scored arousals were linked to automatically scored SpO2 events and defined temporally as pre-event (arousal terminated ≤ 10 s prior to desaturation onset) or within-event (arousal began within the desaturation event or ≤ 5 s after desaturation offset). RESULTS: 5,484 participants (49% female, median age 63 years) were included with 235,996 saturation events. 1.2% of events had pre-event arousals (n = 2,850), while 47.6% had within-event arousals (n = 112,271). Pre-event arousals were associated with faster desaturation rates (standardized effect: 0.54-0.58) and shorter desaturation durations (by 25-36%). Within-event arousals were associated with lower nadirs, longer desaturation durations, and larger desaturation areas (standardized effects: 0.24-0.51). Both arousal types increased resaturation rates, but through different mechanisms: pre-event arousals shortened resaturation durations while within-event arousals increased resaturation height. These effects were amplified with respiratory events, with the strongest associations observed during apnoeas. CONCLUSIONS: Arousals significantly influence SpO2 event architecture, with differential changes seen between desaturation and resaturation parameters.