Brain and Systemic Oxygenation Coupling in Sleep-Disordered Breathing Tied to Cognition in Elderly

Background: Intermittent hypoxia, one of the consequences of sleep-disordered breathing (SDB), could contribute to an increased risk of cognitive decline. However, the association between SDB and cognition varies widely. Methods: Fifty-two community-dwelling healthy older adults (28 women) without dementia were recruited. All participants underwent neuropsychiatric evaluations, simultaneous in-home polysomnography (PSG), and NIRS recordings. We quantified the average coherence between oxy-Hb and SpO2 signals during SDB events to see if it can predict cognitive outcomes in healthy older adults, where higher coherence represents less protection against systemic hypoxia. Results: The mean (SD) coherence of oxy-Hb and SpO2 was 0.16 (0.07). Linear regression analysis showed a significant association between mean coherence and increased age and education-adjusted Stroop Color Word Test scores (t=-.304, p=.004). Whereas, oxy-Hb reduction alone did not show a significant association with cognition, and there were no significant correlations between conventional SDB parameters and cognition. Conclusion: A higher coherence rate of cortical oxy-Hb and systemic SpO2 during SDB possibly reflects a loss of compensatory mechanism against systemic hypoxia and may help stratify older adults with a higher risk for cognitive decline. This is the first report on the association between NIRS parameters in SDB and cognition in older adults.