Validation of the Karolinska sleepiness scale against performance and EEG variables

• Published in: Clinical neurophysiology Vol. 117; no. 7; pp. 1574 - 1581
• Main Authors: Kaida, Kosuke, Takahashi, Masaya, Åkerstedt, Torbjörn, Nakata, Akinori, Otsuka, Yasumasa, Haratani, Takashi, Fukasawa, Kenji
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.07.2006; Elsevier Science
• Subjects: Adult; Analysis of Variance; Biological and medical sciences; Electrodiagnosis. Electric activity recording; Electroencephalography; Female; Fundamental and applied biological sciences. Psychology; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Medicin och hälsovetenskap; Nervous system; Psychomotor Performance - physiology; Reaction Time - physiology; Reproducibility of Results; Sleep - physiology; Sleep. Vigilance; Surveys and Questionnaires; Task Performance and Analysis; The alpha attenuation test (AAT); The Japanese version of the Karolinska sleepiness scale (KSS-J); The Karolinska drowsiness test (KDT); The Karolinska sleepiness scale (KSS); The psychomotor vigilance task (PVT); Vertebrates: nervous system and sense organs; The Karolinska drowsiness test (KDT); The alpha attenuation test (AAT); The Karolinska sleepiness scale (KSS); The Japanese version of the Karolinska sleepiness scale (KSS-J); The psychomotor vigilance task (PVT); Human; Validation; Vigilance; Electrophysiology; Electroencephalography; Eye; Visual system; Electrodiagnosis; Validity; Reaction time; Attenuation; Reliability; Performance
• ISSN: 1388-2457; 1872-8952
• DOI: 10.1016/j.clinph.2006.03.011

The Karolinska sleepiness scale (KSS) is frequently used for evaluating subjective sleepiness. The main aim of the present study was to investigate the validity and reliability of the KSS with electroencephalographic, behavioral and other subjective indicators of sleepiness. Participants were 16 healthy females aged 33–43 (38.1±2.68) years. The experiment involved 8 measurement sessions per day for 3 consecutive days. Each session contained the psychomotor vigilance task (PVT), the Karolinska drowsiness test (KDT—EEG alpha & theta power), the alpha attenuation test (AAT—alpha power ratio open/closed eyes) and the KSS. Median reaction time, number of lapses, alpha and theta power density and the alpha attenuation coefficients (AAC) showed highly significant increase with increasing KSS. The same variables were also significantly correlated with KSS, with a mean value for lapses (r=0.56). The KSS was closely related to EEG and behavioral variables, indicating a high validity in measuring sleepiness. KSS ratings may be a useful proxy for EEG or behavioral indicators of sleepiness.