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Electroencephalography and subjective ratings of sleep deprivation.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine.
Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
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2005 (English)In: Sleep Medicine, ISSN 1389-9457, E-ISSN 1878-5506, Vol. 6, no 3, 231-240 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND AND PURPOSE: Sleep-related vehicle accidents account for many injuries and fatalities each year on monotonous motorways and roads. To effectively prevent such incidents requires greater knowledge of the mechanisms and development of the effects of sleep deprivation. Ten volunteers participated in a laboratory study aimed to analyze the way changes in wakefulness were described in terms of EEG changes and subjective ratings. PATIENTS AND METHODS: For each subject, the study consisted of four testing sessions that varied in length on different days: one session each of 60, 90, and 120 min when sleep-deprived, and one session of 120 min when rested. Changes in wakefulness were analyzed using electroencephalographic recordings and ratings on two different scales, the Karolinska Sleepiness Scale (KSS) and the Category-Ratio Scale (CR-10). RESULTS: The results indicate quite conclusively that significant changes in the perception of sleepiness occur during the first 60-90 min of sedentary, monotonous work. Beyond this time period, subjective and physiological changes remained constant throughout the rest of the 120-min period. CONCLUSION: In general, the subjective rating scales highly and significantly correlated with theta activity in both tired and rested states and with alpha activity in the rested state. Similar results were seen using both subjective rating scales.

Place, publisher, year, edition, pages
2005. Vol. 6, no 3, 231-240 p.
URN: urn:nbn:se:umu:diva-4957DOI: 10.1016/j.sleep.2004.11.012PubMedID: 15854853OAI: diva2:144273
Available from: 2006-02-24 Created: 2006-02-24 Last updated: 2015-01-21Bibliographically approved
In thesis
1. Indicators and predictors of sleepiness
Open this publication in new window or tab >>Indicators and predictors of sleepiness
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sleep is a basic need as important as physical fitness and good nutrition. Without enough sleep, we will create a sleep debt and experience sleepiness. Sleepiness can be defined as the inability to stay awake, a condition that has become a health problem in our 24-hour-7-day-a-week society. Estimates suggest that up to one-third of the population suffers from excessive sleepiness. Among other interactions, sleepiness affects our performance, increasing the risk of being involved in accidents. A considerable portion of work related accidents and injuries are related to sleepiness resulting in large costs for the individuals and society. Professional drivers are one example of workers who are at risk of sleepiness related accidents. Up to 40% of heavy truck accidents could be related to sleepiness. A better knowledge about reliable indicators and predictors of sleepiness is important in preventing sleepiness related accidents.

This thesis investigates both objective and subjective indicators of sleepiness, how these relate to each other, and how their pattern changes over time. The indicators investigated were electroencephalography, heart rate variability, simple reaction time, head movement, and subjective ratings of sleepiness (Study I-IV). In Study V, a questionnaire study was conducted with professional drivers in northern Sweden. This study mainly deals with predictors of sleepiness.

When subjects were sleep deprived both objective and subjective ratings indicated a rapid increase in sleepiness during the first hour of the test followed by a levelling off. This change in pattern was evident for all the indicators except heart rate and heart rate variability. On the other hand, HRV was correlated with the increase of EEG parameters during the post-test sleep period. The changes in pattern of the indicators included in the thesis are analysed in the perspective of temporal patterns and relationships. Of the tested indicators, a subjective rating of sleepiness with CR-10 was considered to be the most reliable indicator of sleepiness.

Of the investigated predictors of sleepiness, prior sleep habits were found to be strongly associated to sleepiness and the sleepiness related symptoms while driving. The influences of driving conditions and individual characteristics on sleepiness while driving were lower.

A multidisciplinary approach when investigating and implementing indicators and predictors of sleepiness is important. In addition to their actual relations to the development of sleepiness, factors such as technical and practical limitations, work, and individual and situational needs must be taken into account.

Place, publisher, year, edition, pages
Umeå: Folkhälsa och klinisk medicin, 2006. 85 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1003
Public health, Sleep Scale (KSS), Category-Ratio Scale (CR-10), sleepiness, sleep, driving, indicator, sleep debt, heart rate variability, electroencephalography (EEG), head movements, performance, truck drivers, sleep habits, predictor, Folkhälsomedicin
National Category
Public Health, Global Health, Social Medicine and Epidemiology
urn:nbn:se:umu:diva-708 (URN)91-7264-017-0 (ISBN)
Public defence
2006-03-17, Stora föreläsningsalen, Arbetslivsinstitutet, petrus laestadiusvägen, Umeå, 09:00 (English)
Available from: 2006-02-24 Created: 2006-02-24 Last updated: 2009-10-30Bibliographically approved

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Nilsson, Leif
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