Event related delta and theta oscillations are reduced in severe obstructive sleep apnea as a possible electrophysiologial evidence of subtle cognitive changes

Abstract

AbstractBackgroundObstructive Sleep Apnea Syndrome (OSAS) is a common sleep disorder that leads to widespread cognitive impairment when left untreated. OSAS is also reported as a risk factor for developing Alzheimer’s disease. Recent studies report a shared pathophysiology between OSAS and Alzheimer’s disease (Polsek et al., 2018; Baril et al., 2018). Working memory and attention related ERP P300 deficits were previously reported (for a review see, Raggi and Ferri, 2012). This study aims to investigate electrophysiological changes by using time‐frequency analysis to gain a better understanding on cognitive impairment in OSAS.Method56 severe OSAS patients and age, education and gender matched 33 healthy controls were participated to the study. Participants completed a classical auditory oddball task. A complex Morlet with Gabor normalization was applied and total power within four frequency bandwidths, delta (0.5‐3.5 Hz), theta (4‐7 Hz), alpha (8‐13 Hz), and beta (15‐30 Hz), was calculated using Event‐Related Spectral Perturbation (ERSP) analyses.ResultOSAS patients had reduced delta and theta ERPS to target stimuli compared to healthy controls in repeated measures ANOVA yielding a significant main GROUP effect (respectively, [F(1,87)=9.181, p=0.003] and [F(1,87)=5.083, p=0.027]). No differences were found on alpha and beta power.ConclusionWe found reduced delta and theta activity in severe OSAS patients. Delta EROs activity is associated with attention and decision making (Başar ve Stampfer, 1985; Stampfer ve Başar, 1985), whereas theta activity was associated with task induced activation of working memory (Yordanova et al. 2000). Reduced delta and theta EROs activity can be useful indices of subtle cognitive impairment in severe OSAS even before neuropsychological test. These results strengthen our understanding of the cognitive changes in OSAS by means of electrophysiological methodologies. This study was supported by Dokuz Eylul University Scientific Research Projects (Project Number: 2014.KB.SAG.058).