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  • Ahlström, Christer, et al. (författare)
  • Fit-for-duty test for estimation of drivers sleepiness level: Eye movements improve the sleep/wake predictor
  • 2013
  • Ingår i: Transportation Research Part C. - : Elsevier. - 0968-090X .- 1879-2359. ; 26, s. 20-32
  • Tidskriftsartikel (refereegranskat)abstract
    • Driver sleepiness contributes to a considerable proportion of road accidents, and a fit-for-duty test able to measure a drivers sleepiness level might improve traffic safety. The aim of this study was to develop a fit-for-duty test based on eye movement measurements and on the sleep/wake predictor model (SWP, which predicts the sleepiness level) and evaluate the ability to predict severe sleepiness during real road driving. Twenty-four drivers participated in an experimental study which took place partly in the laboratory, where the fit-for-duty data were acquired, and partly on the road, where the drivers sleepiness was assessed. A series of four measurements were conducted over a 24-h period during different stages of sleepiness. Two separate analyses were performed; a variance analysis and a feature selection followed by classification analysis. In the first analysis it was found that the SWP and several eye movement features involving anti-saccades, pro-saccades, smooth pursuit, pupillometry and fixation stability varied significantly with different stages of sleep deprivation. In the second analysis, a feature set was determined based on floating forward selection. The correlation coefficient between a linear combination of the acquired features and subjective sleepiness (Karolinska sleepiness scale, KSS) was found to be R = 0.73 and the correct classification rate of drivers who reached high levels of sleepiness (KSS andgt;= 8) in the subsequent driving session was 82.4% (sensitivity = 80.0%, specificity = 84.2% and AUC = 0.86). Future improvements of a fit-for-duty test should focus on how to account for individual differences and situational/contextual factors in the test, and whether it is possible to maintain high sensitive/specificity with a shorter test that can be used in a real-life environment, e.g. on professional drivers.
  • Bellavia, Andrea, et al. (författare)
  • Sleep Duration and Survival Percentiles Across Categories of Physical Activity
  • 2014
  • Ingår i: ; 179:4, s. 484-491
  • Tidskriftsartikel (refereegranskat)abstract
    • The association between long sleep duration and death is not fully understood. Long sleep is associated with low physical activity, which is a strong predictor of death. Our aim was to investigate the association between sleep duration and death across categories of total physical activity in a large prospective cohort of Swedish men and women. We followed a population-based cohort of 70,973 participants (37,846 men and 33,127 women), aged 45-83 years, from January 1998 to December 2012. Sleep duration and physical activity levels were assessed through a questionnaire. We evaluated the association of interest in terms of mortality rates by estimating hazard ratios with Cox regression and in terms of survival by evaluating 15th survival percentile differences with Laplace regression. During 15 years of follow-up, we recorded 14,575 deaths (8,436 men and 6,139 women). We observed a significant interaction between sleep duration and physical activity in predicting death (P < 0.001). Long sleep duration (>8 hours) was associated with increased mortality risk (hazard ratio = 1.24; 95% confidence interval: 1.11, 1.39) and shorter survival (15th percentile difference = -20 months; 95% confidence interval: -30, -11) among only those with low physical activity. The association between long sleep duration and death might be partly explained by comorbidity with low physical activity.
  • Hallvig, David, et al. (författare)
  • Real driving at night - predicting lane departures from physiological and subjective sleepiness
  • 2014
  • Ingår i: Biological Psychology. - : Elsevier. - 0301-0511 .- 1873-6246. ; 101, s. 18-23
  • Tidskriftsartikel (refereegranskat)abstract
    • Only limited information is available on how driving performance relates to physiological and subjective sleepiness on real roads. This relation was the focus of the present study. 33 volunteers drove for 90min on a rural road during the afternoon and night in an instrumented car, while electroencephalography and electrooculography and lane departures were recorded continuously and subjective ratings of sleepiness were made every 5min (Karolinska Sleepiness Scale - KSS). Data was analyzed using Bayesian multilevel modeling. Unintentional LDs increased during night driving, as did KSS and long blink durations(LBD). Lateral position moved to the left . LDs were predicted by self-reported sleepiness and LBDs across time and were significantly higher in individuals with high sleepiness. Removal of intentional LDs, enhanced the KSS/LD relation. It was concluded that LDs, KSS, and LBDs are strongly increased during night driving and that KSS predicts LDs.
  • Hallvig, D., et al. (författare)
  • Sleepy driving on the real road and in the simulator - A comparison
  • 2013
  • Ingår i: Accident Analysis and Prevention. - : Elsevier. - 0001-4575 .- 1879-2057. ; 50, s. 44-50
  • Tidskriftsartikel (refereegranskat)abstract
    • Sleepiness has been identified as one of the most important factors contributing to road crashes. However, almost all work on the detailed changes in behavior and physiology leading up to sleep related crashes has been carried out in driving simulators. It is not clear, however, to what extent simulator results can be generalized to real driving. This study compared real driving with driving in a high fidelity, moving base, driving simulator with respect to driving performance, sleep related physiology (using electroencephalography and electrooculography) and subjective sleepiness during night and day driving for 10 participants. The real road was emulated in the simulator. The results show that the simulator was associated with higher levels of subjective and physiological sleepiness than real driving. However, both for real and simulated driving, the response to night driving appears to be rather similar for subjective sleepiness and sleep physiology. Lateral variability was more responsive to night driving in the simulator, while real driving at night involved a movement to the left in the lane and a reduction of speed, both of which effects were absent in the simulator. It was concluded that the relative validity of simulators is acceptable for many variables, but that in absolute terms simulators cause higher sleepiness levels than real driving. Thus, generalizations from simulators to real driving must be made with great caution.
  • Ingre, M., et al. (författare)
  • Periodic self-rostering in shift work : correspondence between objective work hours, work hour preferences (personal fit), and work schedule satisfaction
  • 2012
  • Ingår i: Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 38:4, s. 327-336
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives The main objective of the present study was to investigate relative personal fit as the association between rated needs and preferences for work hours, on the one hand, and actual work hours, on the other hand, in three groups (hospital, call-center, and police) working with periodic self-rostering. We also examined the association between personal fit and satisfaction with the work schedule and preference for a fixed and regular shift schedule, respectively. Methods We collected questionnaire data and objective work hour data over 6-12 months from the computerized self-rostering system. The response rate of the questionnaire was 69% at the hospital and call-center and 98% among the police. In total, 29 433 shifts for 285 shift workers were included in the study. Data was analyzed by means of mixed ANOVA, Kendal tau correlations and ordinal (proportional odds) logistic regression. Results The results show that evening types worked relatively more hours during the evening and night hours compared to morning types as an indication of relative personal fit. Relative personal fit was also found for long shift, short rest, and morning-, evening- and night-shift frequency, but only personal fit related to morning, evening and night-shift was associated with satisfaction with work hours. Reported conflicts at the workplace about work hours and problems with lack of predictability of time for family/leisure activities, was associated with poor satisfaction and a preference for a fixed shift schedule. Conclusions The present study shows that periodic self-rostering is associated with relative personal fit, in particular with respect to night, evening, and morning work. Personal fit seems to be associated with satisfaction with work hours and may be a moderator of tolerance to shift work exposure.
  • Ivarsson, Malena, et al. (författare)
  • The effect of violent and nonviolent video games on heart rate variability, sleep, and emotions in adolescents with different violent gaming habits
  • 2013
  • Ingår i: Psychosomatic Medicine. - : Lippincott Williams & Wilkins. - 0033-3174 .- 1534-7796. ; 75:4, s. 390-396
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective To study cardiac, sleep-related, and emotional reactions to playing violent (VG) versus nonviolent video games (NVG) in adolescents with different gaming habits.Methods Thirty boys (aged 13-16 years, standard deviation = 0.9), half of them low-exposed (≤1 h/d) and half high-exposed (≥3 h/d) to violent games, played a VG/NVG for 2 hours during two different evenings in their homes. Heart rate (HR) and HR variability were registered from before start until next morning. A questionnaire about emotional reactions was administered after gaming sessions and a sleep diary on the following mornings.Results During sleep, there were significant interaction effects between group and gaming condition for HR (means [standard errors] for low-exposed: NVG 63.8 [2.2] and VG 67.7 [2.4]; for high-exposed: NVG 65.5 [1.9] and VG 62.7 [1.9]; F(1,28) = 9.22, p = .005). There was also a significant interaction for sleep quality (low-exposed: NVG 4.3 [0.2] and VG 3.7 [0.3]); high-exposed: NVG 4.4 [0.2] and VG 4.4 [0.2]; F(1,28) = 3.51, p = .036, one sided), and sadness after playing (low-exposed: NVG 1.0 [0.0] and VG 1.4 [0.2]; high-exposed: NVG 1.2 [0.1] and VG 1.1 [0.1]; (F(1,27) = 6.29, p = .009, one sided).Conclusions Different combinations of the extent of (low versus high) previous VG and experimental exposure to a VG or an NVG are associated with different reaction patterns-physiologically, emotionally, and sleep related. Desensitizing effects or selection bias stand out as possible explanations.
  • Lekander, M., et al. (författare)
  • Subjective health perception in healthy young men changes in response to experimentally restricted sleep and subsequent recovery sleep
  • 2013
  • Ingår i: Brain Behavior and Immunity. - 0889-1591 .- 1090-2139. ; 34, s. 43-46
  • Tidskriftsartikel (refereegranskat)abstract
    • Sleep and subjective health are both prospectively related to objective indices of health and health care use. Here, we tested whether five days with restricted sleep and subsequent recovery days affect subjective health and is related to increased levels of circulating IL-6 and TNF-alpha and fatigue. Nine healthy men (23-28 years) went through a 6-week sleep protocol with subjects as their own controls in a repeated measures design with a total of 11 nights in a sleep laboratory. The experimental part of the protocol included three baseline days (sleep 23-07 h), five days with sleep restriction (03-07 h) and three recovery days (23-07 h) in the sleep laboratory. Subjective health and fatigue was recorded daily. Eight blood samples were drawn each day (every third hour) on 8 days of the protocol and analyzed with respect to IL-6 and TNF-alpha. Subjective health deteriorated gradually during restricted sleep (p = .002) and returned to baseline levels after three days of recovery. IL-6 and TNF-alpha did not change significantly. Fatigue increased gradually during sleep restriction (p = .001), which significantly contributed to the association between restricted sleep and subjective health. The study is the first to show that subjective health is directly responsive to changes in sleep length and related to increased fatigue. Thus, subjective health is differently appraised after manipulation of one of its presumed determinants. Larger experimental studies would be beneficial to further distinguish causation from association regarding the underpinnings of subjective health. (C) 2013 Published by Elsevier Inc.
  • Di Milia, Lee, et al. (författare)
  • Sleepiness, long distance commuting and night work as predictors of driving performance
  • 2012
  • Ingår i: PLoS ONE. - 1932-6203 .- 1932-6203. ; 7:9, s. e45856-
  • Tidskriftsartikel (refereegranskat)abstract
    • Few studies have examined the effect of working night shift and long distance commuting. We examined the association between several sleep related and demographic variables, commuting distance, night work and use of mobile phones on driving performance. We used a prospective design to recruit participants and conducted a telephone survey (n = 649). The survey collected demographic and journey details, work and sleep history and driving performance concerning the day the participant was recruited. Participants also completed the Karolinska Sleepiness Scale and the Epworth Sleepiness Scale. Night workers reported significantly more sleepiness, shorter sleep duration and commuting longer distances. Seven variables were significant predictors of lane crossing. The strongest predictor was acute sleepiness (OR = 5.25, CI, 1.42-19.49, p < 0.01) followed by driving >= 150 kms (OR = 3.61, CI, 1.66-7.81, p < 0.001), obtaining less than 10 hours sleep in the previous 48 hours (OR = 2.58, CI, 1.03-6.46, p < 0.05), driving after night shift (OR = 2.19, CI, 1.24-3.88, p < 0.001), being <43 years old (OR = 1.95, CI, 1.11-3.41, p < 0.05) and using mobile phones during the journey (OR = 1.90, CI, 1.10-3.27, p < 0.05). Sleep related variables, long-distance commuting and night work have a major impact on lane crossing. Several interventions should be considered to reduce the level of sleepiness in night workers.
  • Nordin, M., et al. (författare)
  • Psychometric evaluation and normative data for the Karolinska Sleep Questionnaire
  • 2013
  • Ingår i: Sleep and Biological Rhythms. - Hoboken : Wiley-Blackwell. - 1446-9235 .- 1479-8425. ; 11:4, s. 216-226
  • Tidskriftsartikel (refereegranskat)abstract
    • The study objective was to validate the Karolinska Sleep Questionnaire with regard to dimensionality, internal consistency, and construct and criterion validity. Another objective was to provide normative data. Data from the cross-sectional Vasterbotten Environmental Health Study in Sweden were used. The 3406 participants in this study, 18 to 79 years old, constituted a random sample stratified for age and sex. Along with the Karolinska Sleep Questionnaire, the participants responded to the Hospital Anxiety and Depression Scale, the Perceived Stress Scale, and the Shirom Melamed Burnout Questionnaire for assessing construct validity. Factor analyses of the questions in the Karolinska Sleep Questionnaire that relate to nocturnal sleep revealed the dimensions sleep quality, non-restorative sleep, and sleep apnea. A separate factor analysis on the questions regarding day time sleepiness revealed a sleepiness dimension. The sleep quality, non-restorative sleep, and sleepiness dimensions showed approximate normal distributions, whereas the distribution for sleep apnea was positively skewed. All dimensions showed good internal consistency. Satisfactory construct validity was found for all dimensions. Using the DSM-IV criteria of insomnia, relevant questions in the Karolinska Sleep Questionnaire were combined into an index of nocturnal symptoms of insomnia as were questions of sleep apnea. Prevalences of insomnia and sleep apnea correspond well to those of other studies, indicating good criterion validity. The favorable psychometric properties of the dimensions and indexes from the Karolinska Sleep Questionnaire suggest their use for assessing sleep quality, non-restorative sleep, sleep apnea, sleepiness and nocturnal symptoms of insomnia.
  • Rehman, Javaid-ur, et al. (författare)
  • Sleeping during the day : effects on the 24-h patterns of IGF-binding protein 1, insulin, glucose, cortisol, and growth hormone.
  • 2010
  • Ingår i: European Journal of Endocrinology. - 0804-4643 .- 1479-683X. ; 163:3, s. 383-90
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Disturbed sleep is a major risk factor for metabolic disturbances, including type 2 diabetes, but the involved mechanisms are still poorly understood. We investigated how an acute shift of sleep to the daytime affected IGF-binding protein 1 (IGFBP1), which is a risk factor for diabetes. METHODS: Seven healthy men (age, 22-32 years) participated in a night sleep condition (sleep 2300-0700 h) and a day sleep condition (0700-1500 h) with hourly blood samples taken for 25 h (starting at 1900 h) and isocaloric meals every 4th hour awake. The blood samples were analyzed for IGFBP1, insulin, GH, glucose, and cortisol. RESULT: The acute shift of sleep and meal timing (to 8 h) shifted the 24-h patterns of IGFBP1, glucose, insulin, and GH to a similar degree. However, the day sleep condition also resulted in elevated levels of IGFBP1 (area under curve (AUC)+22%, P<0.05), and reduced glucose levels (AUC-7%, P<0.05) compared with nocturnal sleep. Sleeping during the day resulted in elevated cortisol levels during early sleep and reduced levels in late sleep, but also in increased levels the subsequent evening (P's<0.05). CONCLUSION: Sleep-fasting seems to be the primary cause for the elevation of IGFBP1, irrespective of sleep timing. However, sleeping during the day resulted in higher levels of IGFBP1 than nocturnal sleep, suggesting altered metabolism among healthy individuals, which may have implications for other groups with altered sleep/eating habits such as shift workers. Moreover, sleep and meal times should be accounted for while interpreting IGFBP1 samples.
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