Amplitude coupling is altered in delirium of various etiologies: Results from a retrospective multi-center case-control EEG study

Objective: Delirium manifests with comparable clinical presentations, regardless of its heterogeneous etiology. This suggests a final common pathway such as decreased electroencephalography (EEG) phase coupling. This study investigates if amplitude coupling, another mode of neural communication, is altered in delirium due to different etiologies. Methods: We analyzed EEGs of patients from three sites with either postoperative, poststroke or medical delirium and non-delirious control patients. Amplitude envelope correlation corrected for spatial leakage (AECc) was calculated and Mann-Whitney U-tests were used to compare patients with or without delirium. AECc differences among delirium types were compared using Kruskal-Wallis tests. Results: AECc was significantly increased in delirious (n = 173, age 79.2±9.3 years, 46 % female) as compared to non-delirious (n = 204, age 72.9±13.1 years, 45 % female) patients in the delta (median, effect size of difference: 0.16 vs. 0.12, r = 0.28, p < 0.01) and beta band (0.11 vs. 0.09, r = 0.14, p = 0.04). These changes did not differ among delirium types (p > 0.05). Conclusions: We found modestly higher delta and beta band AECc in delirium compared to non-delirious control patients, regardless of the presumed etiology. Significance: This study provides evidence for altered amplitude coupling as mode of impaired neuronal communication in delirium, the role of which should be investigated in future studies of neural network pathophysiology.