Exclusion of EEG-based arousals in wake epochs of polysomnography leads to underestimation of the arousal index

Danielle L Wilson; Julie Tolson; Thomas J Churchward; Kerri Melehan; Fergal J O'Donoghue; Warren R Ruehland

doi:10.5664/jcsm.9878

Exclusion of EEG-based arousals in wake epochs of polysomnography leads to underestimation of the arousal index

J Clin Sleep Med. 2022 May 1;18(5):1385-1393. doi: 10.5664/jcsm.9878.

Authors

Danielle L Wilson^{1

2}, Julie Tolson^{1

2

3}, Thomas J Churchward^{1

2}, Kerri Melehan^{4

5}, Fergal J O'Donoghue^{1

2

3}, Warren R Ruehland^{1

2}

Affiliations

¹ Department of Respiratory and Sleep Medicine, Austin Hospital, Heidelberg, Australia.
² Institute for Breathing and Sleep, Austin Hospital, Heidelberg, Australia.
³ Faculty of Medicine, University of Melbourne, Melbourne, Australia.
⁴ Royal Prince Alfred Hospital, Sydney, Australia.
⁵ Faculty of Medicine and Health, University of Sydney, Sydney, Australia.

Abstract

Study objectives: There is an internal contradiction in current American Academy of Sleep Medicine standards for arousal index (AI) calculation in polysomnography: Arousals in sleep and wake epochs are counted, but only sleep time is used in the denominator. This study aimed to investigate the impact of including arousals scored in wake epochs on the AI.

Methods: We compared AIs including (AI_inc) vs excluding (AI_exc) awake-epoch arousals from 100 consecutive polysomnograms conducted for investigation of possible obstructive sleep apnea. To determine the AI that most closely approximated "truth," AI_inc and AI_exc were compared to an AI calculated from continuous sleep analysis (AI_cont) in a 20-polysomnogram subgroup of patients.

Results: The median (interquartile range) increase in AI_inc was 5.2 events/h (3.5-8.1) vs AI_exc (AI_inc = 28.0 events/h [18.4-38.9] vs AI_exc = 22.9 events/ h [13.1-31.3]), equating to an increase of 25.3% (15.6-40.8). As the AI increased, the difference increased (P < .001), with decreasing sleep efficiency and an increasing apnea-hypopnea index as the strongest predictors of the difference between AI_exc and AI_inc. The absolute AI_exc-AI_cont difference (7.7 events/h [5.1-13.6]) was significantly greater than the AI_inc-AI_cont difference (1.2 events/h [0.6-5.7]; z = -3.099; P = .002).

Conclusions: There was a notable increase in AI when we included wake-epoch arousals, particularly in patients with more severe obstructive sleep apnea or reduced sleep efficiency. However, the AI including wake-epoch arousals best matched the "true" continuous sleep-scoring AI. Our study informs clinical and research practice, highlights epoch scoring pitfalls, and supports the current American Academy of Sleep Medicine standard arousal reporting approach for future standards.

Citation: Wilson DL, Tolson J, Churchward TJ, Melehan K, O'Donoghue FJ, Ruehland WR. Exclusion of EEG-based arousals in wake epochs of polysomnography leads to underestimation of the arousal index. J Clin Sleep Med. 2022;18(5):1385-1393.

Keywords: analysis; arousal; continuous; epoch; polysomnography; wake.

MeSH terms

Arousal*
Electroencephalography
Humans
Polysomnography
Sleep
Sleep Apnea, Obstructive* / diagnosis