Quantitative Electroencephalogram Changes before and after Postoperative Delirium: a prospective, multicenter, cohort study

BACKGROUND: Delirium occurs frequently after major surgery in older adults and is associated with long-term cognitive dysfunction. While postoperative delirium (POD) shows electroencephalographic (EEG) changes during the acute phase, it remains unclear whether quantitative EEG alterations precede or persist after POD. Identifying such patterns could reveal risk markers and mechanisms of long-term cognitive dysfunction.

METHODS: In this prospective multicenter, cohort study, EEG recordings were obtained in patients aged ≥65 years before and three months after major elective surgery without pre-existent cognitive dysfunction, and in non-surgical controls. We analyzed quantitative EEG measures that show alterations during acute delirium, namely: relative power, phase-based and amplitude-based functional connectivity, spectral variability and signal complexity. Linear mixed models were used to assess effects of time, surgery, and POD on these EEG measures.

RESULTS: Of 379 enrolled surgical patients, 330 had sufficient EEG data quality, of which 59 (18%) developed POD. Fifty-seven non-surgical controls were included and served as reference. At baseline, future POD patients exhibited significantly lower beta amplitude based connectivity (β= -0.36, pcorrected=0.04). No other EEG measures showed significant differences between groups at baseline. Three months after surgery, no persistent changes in quantitative EEG characteristics were observed in relation to POD occurrence or surgery alone.

CONCLUSIONS: This study identified reduced preoperative beta amplitude-based connectivity as a possible marker of neurophysiological vulnerability for POD. However, the absence of significant longitudinal changes in quantitative EEG measures suggests that resting-state EEG networks may functionally recover or compensate in this cohort at three months postoperative.