title: The effects of sleep debt and monotonous work on sleepiness and performance during a 12-h dayshift.
abstract: The study examined the effects of the amount of preceding sleep and work pace on sleepiness and cognitive performance during a 12-h dayshift. Twelve process operators (aged 28-56 years) completed a study with four single 12-h dayshifts and preceding night sleep in the laboratory. A simulated distillation process served as a work task. The 12-h shifts differed from each other in terms of the amount of preceding night sleep (23:00-06:30 hours or 2:30-6:30 hours) and work pace (slow or fast). All shifts contained four work simulation sessions of 1.5 h, and each of them included a 15-min alarm session. Cognitive performance was also measured with a 10-choice reaction time test and a mental subtraction test. Objective sleepiness was measured with a continuous electroencephalography/electro-oculography (EEG/EOG) recording during the work periods and with a sleep latency test. Subjective sleepiness at work was measured with the Karolinska Sleepiness Scale. Sleep debt increased the proportion of EEG/EOG-defined and subjective sleepiness at work, but did not impair work or test performance. The fatiguing effect of monotonous work as indicated by EEG/EOG-defined sleepiness was comparable with the effect of sleep debt. The alarm epochs in the middle of monotonous work temporarily decreased EEG/EOG-defined sleepiness. Sleep debt or monotonous work did not have a significant effect on the results of the sleep latency test. None of the sleepiness or performance measures indicated the impairment of a subject's functional capacity at the end of the 12-h shift. Our results suggest that monotonous work is at least as harmful as moderate sleep debt for alertness at work. The results support the view that the last hours of a single 12-h dayshift with frequent pauses are not associated with an increase in sleepiness or performance errors.
authors.affiliation: Brain and Work Research Units, Finnish Institute of Occupational Health, Helsinki, Finland. mikael.sallinen@ttl.fi
authors.forename: Mikael
authors.initials: M
authors.lastname: Sallinen
authors.forename: Mikko
authors.initials: M
authors.lastname: Härmä
authors.forename: Ritva
authors.initials: R
authors.lastname: Akila
authors.forename: Anu
authors.initials: A
authors.lastname: Holm
authors.forename: Ritva
authors.initials: R
authors.lastname: Luukkonen
authors.forename: Hannu
authors.initials: H
authors.lastname: Mikola
authors.forename: Kiti
authors.initials: K
authors.lastname: Müller
authors.forename: Jussi
authors.initials: J
authors.lastname: Virkkala
mesh_terms: D000328:Adult; D000339:Affect; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology*; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000209:etiology*; D004569:Electroencephalography; D004585:Electrooculography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D017286:Polysomnography; D011930:Reaction Time; D012720:Severity of Illness Index; D012892:Sleep Deprivation / Q000150:complications* / Q000175:diagnosis; D012894:Sleep Stages / Q000502:physiology; D017132:Workplace / Q000523:psychology*