Neurophysiological patterns reflecting vulnerability to delirium subtypes: a resting-state EEG and event-related potential study

Monique S Boord; Daniel Feuerriegel; Scott W Coussens; Daniel H J Davis; Peter J Psaltis; Marta I Garrido; Alice Bourke; Hannah A D Keage

doi:10.1093/braincomms/fcae298

Neurophysiological patterns reflecting vulnerability to delirium subtypes: a resting-state EEG and event-related potential study

Brain Commun. 2024 Sep 5;6(5):fcae298. doi: 10.1093/braincomms/fcae298. eCollection 2024.

Authors

Monique S Boord^{1

2}, Daniel Feuerriegel³, Scott W Coussens¹, Daniel H J Davis⁴, Peter J Psaltis^{5

6

7}, Marta I Garrido^{3

8}, Alice Bourke⁹, Hannah A D Keage¹

Affiliations

¹ Cognitive Ageing and Impairment Neurosciences Laboratory, Justice and Society, University of South Australia, Adelaide, 5072, South Australia, Australia.
² College of Education, Psychology and Social Work, Flinders University, Adelaide, 5042, South Australia, Australia.
³ Melbourne School of Psychological Sciences, University of Melbourne, Melbourne, 3052, Victoria, Australia.
⁴ MRC Unit for Lifelong Health and Ageing, UCL, London, WC1E 6BT, UK.
⁵ Vascular Research Centre, Heart and Vascular Program, Lifelong Health Theme, South Australian Health and Medical Research Institute, Adelaide, 5000, South Australia, Australia.
⁶ Adelaide Medical School, University of Adelaide, Adelaide, 5005, South Australia, Australia.
⁷ Department of Cardiology, Royal Adelaide Hospital, Central Adelaide Local Health Network, Adelaide, 5000, South Australia, Australia.
⁸ Graeme Clark Institute for Biomedical Engineering, University of Melbourne, Melbourne, 3052, Victoria, Australia.
⁹ Aged Care, Rehabilitation and Palliative Care (Medical), Northern Adelaide Local Health Network, Adelaide, 5092, South Australia, Australia.

Abstract

Delirium is a common and acute neurocognitive disorder in older adults associated with increased risk of dementia and death. Understanding the interaction between brain vulnerability and acute stressors is key to delirium pathophysiology, but the neurophysiology of delirium vulnerability is not well defined. This study aimed to identify pre-operative resting-state EEG and event-related potential markers of incident delirium and its subtypes in older adults undergoing elective cardiac procedures. This prospective observational study included 58 older participants (mean age = 75.6 years, SD = 7.1; 46 male/12 female); COVID-19 restrictions limited recruitment. Baseline assessments were conducted in the weeks before elective cardiac procedures and included a 4-min resting-state EEG recording (2-min eyes open and 2-min eyes closed), a 5-min frequency auditory oddball paradigm recording, and cognitive and depression examinations. Periodic peak power, peak frequency and bandwidth measures, and aperiodic offsets and exponents were derived from resting-state EEG data. Event-related potentials were measured as mean component amplitudes (first positive component, first negative component, early third positive component, and mismatch negativity) following standard and deviant auditory stimuli. Incident delirium occurred in 21 participants: 10 hypoactive, 6 mixed, and 5 hyperactive. Incident hyperactive delirium was associated with higher pre-operative eyes open (P = 0.045, d = 1.0) and closed (P = 0.036, d = 1.0) aperiodic offsets. Incident mixed delirium was associated with significantly larger pre-operative first positive component amplitudes to deviants (P = 0.037, d = 1.0) and larger third positive component amplitudes to standards (P = 0.025, d = 1.0) and deviants (P = 0.041, d = 0.9). Other statistically non-significant but moderate-to-large effects were observed in relation to all subtypes. We report evidence of neurophysiological markers of delirium risk weeks prior to elective cardiac procedures in older adults. Despite being underpowered due to COVID-19-related recruitment impacts, these findings indicate pre-operative dysfunction in neural excitation/inhibition balance associated with different delirium subtypes and warrant further investigation on a larger scale.

Keywords: EEG; delirium; event-related potentials; pathophysiology.

Grants and funding

WT_/Wellcome Trust/United Kingdom