Hypoxic Load and Average Oxygen-Saturation During Sleep and Wake Are Associated With Cognitive Function in Obstructive Sleep Apnea.

Cognitive processes commonly affected by obstructive sleep apnea (OSA) are more strongly associated with hypoxic load parameters than the apnea-hypopnea index (AHI). Additionally, lower SpO2 during wake affects cognition, emphasising the need for concurrent assessment with sleep SpO2. This study examined which OSA severity parameters best predict cognitive performance and the role of wake SpO2. Sixty-one participants (53% female), with an average age of 46.9 years (range 19-79), completed a three-night self-applied polysomnography (PSG) and a digital neurocognitive battery. Oxygen saturation-based PSG parameters predicted immediate recall, vigilance, and processing speed, whereas the AHI did not. Greater hypoxic severity from 100% SpO2 baseline was the strongest predictor of slower processing speed (χ 2(6) = 17.74, p = 0.007) (β = -5.72, p = 0.023). Lower average SpO2 during sleep most strongly predicted immediate recall (χ 2(6) = 28.94, p < 0.001) (β = 0.38, p = 0.03) and vigilance (χ 2(6) = 16.72, p = 0.010) (β = 0.15, p = 0.002). Additionally, lower wake SpO2 was associated with reduced vigilance performance. The results confirm the AHI's limitation in capturing OSA symptom severity and highlight the stronger associations between oxygen saturation-based OSA parameters and cognitive abilities. Furthermore, we recommend incorporating wake SpO2 measures in sleep research to gain a more comprehensive understanding of the relationship between SpO2 and cognitive abilities.