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Subjective sleepiness is a sensitive indicator of insufficient sleep and impaired waking function
Stockholm University, Faculty of Social Sciences, Stress Research Institute. Karolinska Institutet. (Biologisk psykologi och behandlingsforskning)
Stockholm University, Faculty of Social Sciences, Stress Research Institute. (Biologisk psykologi och behandlingsforsknig)
2014 (English)In: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, no 3, 240-252 p.Article in journal (Refereed) Published
Abstract [en]

The main consequence of insufficient sleep is sleepiness. While measures of sleep latency, continuous encephalographical/electro-oculographical (EEG/EOG) recording and performance tests are useful indicators of sleepiness in the laboratory and clinic, they are not easily implemented in large, real-life field studies. Subjective ratings of sleepiness, which are easily applied and unobtrusive, are an alternative, but whether they measure sleepiness sensitively, reliably and validly remains uncertain. This review brings together research relevant to these issues. It is focused on the Karolinska Sleepiness Scale (KSS), which is a nine-point Likert-type scale. The diurnal pattern of sleepiness is U-shaped, with high KSS values in the morning and late evening, and with great stability across years. KSS values increase sensitively during acute total and repeated partial sleep deprivation and night work, including night driving. The effect sizes range between 1.5 and 3. The relation to driving performance or EEG/EOG indicators of sleepiness is highly significant, strongly curvilinear and consistent across individuals. High (>6) KSS values are associated particularly with impaired driving performance and sleep intrusions in the EEG. KSS values are also increased in many clinical conditions such as sleep apnea, depression and burnout. The context has a strong influence on KSS ratings. Thus, physical activity, social interaction and light exposure will reduce KSS values by 1-2 units. In contrast, time-on-task in a monotonous context will increase KSS values by 1-2 units. In summary, subjective ratings of sleepiness as described here is as sensitive and valid an indicator of sleepiness as objective measures, and particularly suitable for field studies.

Place, publisher, year, edition, pages
2014. Vol. 23, no 3, 240-252 p.
Keyword [en]
driving, EEG, EOG, ratings, shift work, sleep, sleepiness, sleep deprivation, work
National Category
URN: urn:nbn:se:su:diva-105906DOI: 10.1111/jsr.12158ISI: 000336379700002Local ID: P-3158OAI: diva2:733360
Forte, Swedish Research Council for Health, Working Life and Welfare


Available from: 2014-07-09 Created: 2014-07-08 Last updated: 2014-07-24Bibliographically approved

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Åkerstedt, Torbjörn
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