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  • Anund, A, et al. (författare)
  • The effects of driving situation on sleepiness indicators after sleep loss: a driving simulator study
  • 2009
  • Ingår i: Industrial Health. - 0019-8366 .- 1880-8026. ; 47:4, s. 393-401
  • Tidskriftsartikel (refereegranskat)abstract
    • Almost all studies of sleepy driving are carried out in driving simulators and with monotonous road conditions (no interaction with other cars). The present study investigated indicators of sleepy driving in a more challenging scenario after a night awake. 17 participants drove a high fidelity moving base driving simulator experiment while sleepiness was monitored physiologically and behaviourally. Short periods of situations of free driving (no other vehicles) alternated with short periods of following another vehicle (car following) with and without the possibility to overtake. The result showed that a night of prior sleep loss increased sleepiness levels at the wheel (eye closure duration and lateral variability) compared to after a night of normal sleep. Blink duration while overtaking was significantly lower compared to the other situations, it was at the same level as after night sleep. Speed when passing a stopped school bus was not significantly affected by sleepiness. However the warning caused a more rapid reduction of speed. In conclusion, a moderately challenging driving contest did not affect sleepiness indicators, but a very challenging one did so (overtaking). This suggests that it is important to monitor the driving situation in field operational tests of sleepy driving.
  • Dahlgren, A, et al. (författare)
  • Day to day variation in saliva cortisol-Relation with sleep, stress and self-rated health
  • 2009
  • Ingår i: Biological Psychology. - 0301-0511. ; 82:2, s. 149-155
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective was to examine the day-to-day variation in cortisol among healthy individuals and its relation to the time of saliva sampling, work, stress and fatigue. During 4 consecutive weeks, 14 office workers provided saliva samples (at awakening, 15 min after awakening and at bedtime) and made diary ratings for each day. Results showed a variation in cortisol values between participants but also within individuals. After controlling for the individual differences, results showed that low cortisol levels in the morning were associated with sleepiness at awakening and anxiety, exhaustion, and poor health the day before. High evening levels of cortisol were associated with symptoms of stress and poor self-rated health. Further analysis of the cortisol awakening response (CAR) showed that all participants had a mixture of both a positive and negative responses. During mornings with a negative response participants stayed in bed for a longer time after the initial awakening, which might be a sign of snoozing, thus missing the awakening response.
  • Ingre, Michael, et al. (författare)
  • Sleep length as a function of morning shift-start time in irregular shift schedules for train drivers : self-rated health and individual differences.
  • 2008
  • Ingår i: Chronobiol Int. - 1525-6073. ; 25:2, s. 349-58
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Sleep length as a function of morning shift-start time in irregular shift schedules for train drivers: self-rated health and individual differences.</p><p>Ingre M, Kecklund G, Akerstedt T, Söderström M, Kecklund L.</p><p>Stress Research Institute, Stockholm University, Sweden. michael.ingre@stressforskning.su.se</p><p>Forty-six male train drivers (mean age = 46.5, SD = 5.1) were recruited to participate in a diary study for 14 consecutive days with questions about their sleep and working hours. A polynomial mixed-effect regression model showed a curvilinear relation ( p &lt; .001) between shift-start time and sleep duration for shifts starting at 03:00-12:00 hand with a near linear increase for ones starting between 04:30 and 09:00 h of approximately 0.7 h for every 1 h the shift was delayed. The longest sleeps were estimated at approximately 8 h before shifts that started at approximately 10:00 h. The shortest sleeps were found for shifts that started before 04:30 h and were estimated at approximately 5 h. Individual differences were estimated with a random-effect standard deviation of 0.51 h, independent of shift start time ( p = .005). One-half of the between-subject variance was explained by subjective health. A one-step decrease in health was associated with a 26 min increase in sleep length. The results have practical implications for constructing shift schedules. Early morning shifts reduced sleep length substantially and should be mixed with later start hours to avoid the accumulation of sleep dept. Delaying the shift-start past 10:00 h had little effect on sleep opportunity; however, delaying shift-start to between 04:30 and 9:00 h had a strong impact on sleep length, with 70% of the extra time used for sleep, suggesting large positive effects for this range of shift-start times.</p>
  • Kecklund, Lena, et al. (författare)
  • The TRAIN-project: Effects of Organizational Factors, Automatic Train Control, Work Hours, and Environment: Suggestions for Safety-Enhancing Measures
  • 2003
  • Ingår i: Proceedings of the Human Factors and Ergonomic Society, 47th Annual Meeting. ; s. 1835-1839
  • Konferensbidrag (refereegranskat)abstract
    • <p>The purpose of the TRAIN project was to describe and analyse the train drivers information environment, working hours, work situation and work environment and their effect on drivers' behaviour and the train driver system safety as well as to propose safety enhancing measures. The results indicate several problems of significance to the train driver system safety, which have been grouped into three main areas; organizational support functions, information environment including cognitive ergonomics and ATC and also working hours, work situation and work environment.</p>
  • Persson, Roger, et al. (författare)
  • Effects of the implementation of an 84-hour workweek on neurobehavioral test performance and cortisol responsiveness during testing.
  • 2003
  • Ingår i: Scandinavian Journal of Work, Environment and Health. - Finnish Institute of Occupational Health. - 0355-3140. ; 29:4, s. 261-269
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES: This study examined whether long workhours in combination with an extended workweek (12 hours/7 days), as requested by the workers, impaired attention and cognitive performance and whether the degree of hypothalamic-pituitary-adrenal (HPA) activation was related to the response to the performance tasks. METHODS: A group of 41 male construction workers between 21 and 60 (mean 39) years of age who worked 84 hours a week, with alternate weeks off, was compared with a group of 23 male construction workers between 24 and 65 (mean 43) years of age who had a traditional 40-hour work schedule. Neurobehavioral test performance, self-ratings of fatigue and sleepiness, and salivary cortisol levels were evaluated in a counterbalanced repeated-measures design. RESULTS: The 84-hour group did not show any signs of reduced test performance or elevated fatigue and sleepiness. The 84-hour group had faster reaction times on day 7 than on days 1 and 5. Although the expected activation of the HPA axis was only found in the total study sample when workdays 1 and 5 were collapsed, the HPA activation can be considered normal. CONCLUSIONS: The results suggest that an 84-hour work regimen in response to requests from workers does not induce more performance deficits than an ordinary 40-hour workweek. An extended work schedule of 84 hours cannot in the short-term be considered to affect basic mental capabilities negatively.
  • Radun, Igor, et al. (författare)
  • Company employees as experimental participants in traffic safety research : : prevalence and implications
  • 2018
  • Ingår i: Transportation Research Part F: Traffic Psychology and Behaviour. - Stockholm : Karolinska Institutet, Dept of Learning, Informatics, Management and Ethics. - 1369-8478. ; 92.
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of company employees as experimental participants when testing products, technology or paradigms developed by the same company raises questions about bias in results and research ethics. We aimed to investigate the prevalence of studies authored by car company researchers with car company employees as participants, to assess the risk of bias in such studies, to investigate journal editors’ opinions in the field of traffic safety regarding these procedures, and to offer a general discussion about ethical and methodological implications. Three types of data were collected. We (i) examined guidelines and recommendations for authors in eleven selected peer-reviewed journals in the area of traffic safety; (ii) surveyed editors of these journals; and (iii) reviewed articles authored by researchers from a selected group of car manufacturers and published in these journals during 2011-2015. Guidelines and recommendations for authors in the included journals did not mention whether and under what circumstances company employees can be research participants, nor did publishers’ general guidelines. However, three out of the four editors who responded to our survey believed that this issue of private company researchers using participants from the same company deserves to be explicitly addressed in their journal’s guide for authors. The total number of regular articles and conference papers during 2011-2015 in the eleven journals reviewed was 6763; 95 (1.4%) listed at least one car manufacturer in the authors’ affiliations; and out of these, nine included company employees as participants. In summary, company employees are seldom (0.13%) used as research participants in traffic safety research. Nevertheless, the use of company employees as research participants raises questions about bias in results as well as about incursions into the participants’ autonomy.
  • Sandberg, D, et al. (författare)
  • Detecting driver sleeepiness using optimized non-linear combinations of sleepiness indicators
  • 2011
  • Ingår i: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050. ; 12:1, s. 97-108
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper addresses the problem of detecting sleepiness in car drivers. First, a variety of sleepiness indicators (based on driving behavior) proposed in the literature were evaluated. These indicators were then subjected to parametric optimization using stochastic optimization methods. To improve performance, the functional form of some of the indicators was generalized before optimization. Next, using a neural network, the best performing sleepiness indicators were combined with a mathematical model of sleepiness, i.e., the sleep/wake predictor (SWP). The analyses were based on data obtained from a study that involved 12 test subjects at the moving-base driving simulator at the Swedish National Road and Transportation Research Institute (VTI), Linkping, Sweden. The data were derived from 12 1-h driving sessions for each test subject, with varying degrees of sleepiness. The performance measure (range [0,1]) for indicators was taken as the average of sensitivity and specificity. Starting with indicators proposed in the literature, the best such indicator, i.e., the standard deviation of the yaw angle, reached a performance score of 0.72 on previously unseen test data. It was found that indicators based on a given signal gave essentially equal performance after parametric optimization, but in no case was it better than 0.72. The best generalized indicator (the generic variability indicator) obtained a performance score of 0.74. SWP achieved a score of 0.78. However, by nonlinearly combining SWP with the generic variability indicator, a score of 0.83 was obtained. Thus, the results imply that a nonlinear combination of a measure based on driving behavior with a model of sleepiness significantly improves driver sleepiness detection.
  • Santoft, Fredrik, et al. (författare)
  • Mediators of Change in Cognitive Behavior Therapy for Clinical Burnout
  • 2019
  • Ingår i: Behavior Therapy. - 0005-7894 .- 1878-1888. ; 50:3, s. 475-488
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Evidence supporting the effectiveness of cognitive behavior therapy (CBT) for stress-related illness is growing, but little is known about its mechanisms of change. The aim of this study was to investigate potential mediators of CBT for severe stress in form of clinical burnout, using an active psychological treatment as comparator. We used linear mixed models to analyze data from patients (N = 82) with clinical burnout who received either CBT or another psychological treatment in a randomized controlled trial. Potential mediators (i.e., sleep quality, behavioral activation, perceived competence, and therapeutic alliance) and outcome (i.e., symptoms of burnout) were assessed weekly during treatment. The results showed that the positive treatment effects on symptoms of burnout favoring CBT (estimated between-group d = 0.93) were mediated by improvements in sleep quality, ab = -0.017,95% CIasymmetric [-0.037, -0.002], and increase in perceived competence, ab = -0.037, 95% CIasymmetric [-0.070, -0.010]. Behavioral activation, ab = -0.004 [-0.016, 0.007], and therapeutic alliance, ab = 0.002 [-0.006, 0.011], did not significantly mediate the difference in effects between the treatments. Improving sleep quality and increasing perceived competence may thus constitute important process goals in order to attain symptom reduction in CBT for clinical burnout.</p>
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