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Symptoms of sleepiness while driving and their relationship to prior sleep, work and individual characteristics.
Umeå University, Faculty of Medicine, Public Health and Clinical Medicine.
2006 (English)In: Transportation Research Part F: Traffic Psychology and Behaviour, ISSN 1369-8478, Vol. 9, no 3, 207-226 p.Article in journal (Refereed) Published
Abstract [en]

In total, 154 lorry and bus drivers participated in a questionnaire study dealing with sleepiness in traffic. The questionnaire included questions about sleep before work, appearance of sleepiness, the type of sleepiness they experienced while driving, and ways to counter sleepiness while driving. Driver sleepiness was analysed with respect to age, type of driving, traffic intensity, experience of work, and sleep before work. About 14% of the drivers reported regular sleepiness while driving, 33% had occasionally fought sleepiness while driving, and 8% had experienced nodding of the head while driving. The majority of the drivers had once been so tired that they had to stop driving. Sleepiness normally occurred between 03.00 and 06.00, at the end of longer trips, and was most frequently appeared in autumn. Poor sleep and poor working hours were considered as the most important causes to sleepiness. Eye tiredness, yawning, difficulties concentrating on the road, and difficulties keeping one’s thoughts together: these were the most frequently reported symptoms of sleepiness. More sleeping hours before work, better working hours, naps during work, listening to the radio, conversations, and lowering the cabin temperature were the most frequently mentioned countermeasures. The appearances of sleepiness while driving was strongly correlated to lower sleep hours and lower sleep quality before work. Age, type of work, or work experience did not interfere with sleepiness in the investigated group in any systematic way.

Place, publisher, year, edition, pages
2006. Vol. 9, no 3, 207-226 p.
Keyword [en]
Sleepiness; Sleep hours; Drivers; Survey
URN: urn:nbn:se:umu:diva-4961DOI: 10.1016/j.trf.2006.01.001OAI: diva2:144277
Available from: 2006-02-24 Created: 2006-02-24Bibliographically 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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