Subjective and Objective Sleepiness in the Active Individual

TLDR

Eight subjects were kept awake and active overnight in a sleep lab isolated from environmental time cues while ambulatory EEG and EOG were continuously recorded, with sleepiness ratings every two hours and short EEG test sessions, and the EEG was subjected to spectral analysis and EOG visually scored for slow rolling eye movements. Intrusions of slow rolling eye movements and increased alpha and theta power during open‑eyed activity strongly differentiated high from low subjective sleepiness, with high intraindividual correlations, but physiological indices only appeared when subjective sleepiness reached extreme levels, supporting the use of ambulatory EEG/EOG to quantify sleepiness.

Abstract

AbstractEight subjects were kept awake and active overnight in a sleep lab isolated from environmental time cues. Ambulatory EEG and EOG were continuously recorded and sleepiness ratings carried out every two hours as was a short EEG test session with eyes open for 5 min and closed for 2 min. The EEG was subjected to spectral analysis and the EOG was visually scored for slow rolling eye movements (SEM). Intrusions of SEM and of alpha and theta power density during waking, open-eyed activity strongly differentiated between high and low subjective sleepiness (the differentiation was poorer for closed eyes) and the mean intraindividual correlations between subjective and objective sleepiness were very high. Still, the covariation was curvilinear; physiological indices of sleepiness did not occur reliably until subjective perceptions fell between "sleepy" and "extremely sleepy-fighting sleep"; i.e. physiological changes due to sleepiness are not likely to occur until extreme sleepiness is encountered. The results support the notion that ambulatory EEG/EOG changes may be used to quantify sleepiness.Key Words: sleepinessspectral analysispolysomnographyEEGEOGratings