Construction and validation of the EEG analogues of the Karolinska sleepiness scale based on the Karolinska drowsiness test.

OBJECTIVE: Simple methods of sleepiness assessment are greatly needed for both fundamental research and practical applications. The Karolinska drowsiness test (KDT) was applied to construct physiological alertness scales and to validate them against such well-known instrument of subjective sleepiness assessment as the Karolinska sleepiness scale (KSS).
METHODS: Seven-min EEG recordings were obtained with 2-h interval from frontal and occipital derivations during the last 32-50 h of 44-61-h wakefulness of 15 healthy study participants. Occipital alpha-theta power difference and frontal and occipital scores on the 2nd principal component of the EEG spectrum were calculated for each one-min interval of 5-min eyes closed section of the record.
RESULTS: To obtain scores (from 0 to 5) on alertness scales for each of these EEG indexes, all positive one-min values of the index were assigned to 1, and all remaining (negative) values were assigned to 0. Scores on any of the physiological alertness scales were found to be strongly associated with KSS scores.
CONCLUSION: Physiological analogues of KSS were offered by utilising the EEG recordings on eyes closed interval of KDT. SIGNIFICANCE: The constructed physiological scales can help in improving validity and user-friendliness of the field and laboratory methods of quantification of drowsy state.