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Sökning: WFRF:(Akerstedt Torbjorn)

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  • Ahlstrom, Christer, et al. (författare)
  • The impact of driver sleepiness on fixation-related brain potentials
  • 2020
  • Ingår i: Journal of Sleep Research. - : Wiley-Blackwell Publishing Inc.. - 1365-2869 .- 0962-1105. ; 29:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of driver sleepiness are often quantified as deteriorated driving performance, increased blink durations and high levels of subjective sleepiness. Driver sleepiness has also been associated with increasing levels of electroencephalogram (EEG) power, especially in the alpha range. The present exploratory study investigated a new measure of driver sleepiness, the EEG fixation-related lambda response. Thirty young male drivers (23.6 +/- 1.7 years old) participated in a driving simulator experiment in which they drove on rural and suburban roads in simulated daylight versus darkness during both the daytime (full sleep) and night-time (sleep deprived). The results show lower lambda responses during night driving and with longer time on task, indicating that sleep deprivation and time on task cause a general decrement in cortical responsiveness to incoming visual stimuli. Levels of subjective sleepiness and line crossings were higher under the same conditions. Furthermore, results of a linear mixed-effects model showed that low lambda responses are associated with high subjective sleepiness and more line crossings. We suggest that the fixation-related lambda response can be used to investigate driving impairment induced by sleep deprivation while driving and that, after further refinement, it may be useful as an objective measure of driver sleepiness.
  • 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.
  • Ahlström, Christer, 1977-, et al. (författare)
  • The effect of daylight versus darkness on driver sleepiness : A driving simulator study
  • 2017
  • Ingår i: Journal of Sleep Research. - : Wiley-Blackwell Publishing Inc.. - 0962-1105 .- 1365-2869.
  • Tidskriftsartikel (refereegranskat)abstract
    • Driver sleepiness studies are often carried out with alert drivers during daytime and sleep-deprived drivers during night-time. This design results in a mixture of different factors (e.g. circadian effects, homeostatic effects, light conditions) that may confound the results. The aim of this study was to investigate the effect of light conditions on driver sleepiness. Thirty young male drivers (23.6 ± 1.7 years old) participated in a driving simulator experiment where they drove on a rural road. A 2 × 2 design was used with the conditions daylight versus darkness, and daytime (full sleep) versus night-time (sleep deprived). The results show that light condition had an independent effect on the sleepiness variables. The subjective sleepiness measured by Karolinska Sleepiness Scale was higher, lateral position more left-oriented, speed lower, electroencephalogram alpha and theta higher, and blink durations were longer during darkness. The number of line crossings did not change significantly with light condition. The day/night condition had profound effects on most sleepiness indicators while controlling for light condition. The number of line crossings was higher during night driving, Karolinska Sleepiness Scale was higher, blink durations were longer and speed was lower. There were no significant interactions, indicating that light conditions have an additive effect on sleepiness. In conclusion, Karolinska Sleepiness Scale and blink durations increase primarily with sleep deprivation, but also as an effect of darkness. Line crossings are mainly driven by the need for sleep and the reduced alertness at the circadian nadir. Lane position is, however, more determined by light conditions than by sleepiness.
  • Akerstedt, Torbjorn, et al. (författare)
  • Predicting long-term sickness absence from sleep and fatigue.
  • 2007
  • Ingår i: J Sleep Res. - 0962-1105. ; 16:4, s. 341-5
  • Tidskriftsartikel (övrigt vetenskapligt)abstract
    • Predicting long-term sickness absence from sleep and fatigue.Akerstedt T, Kecklund G, Alfredsson L, Selen J.Institute for Psychosocial Medicine, Public Health Sciences, Karolinska Institutet, Stockholm, Sweden. torbjorn.akerstedt@ipm.ki.seDisturbed or shortened sleep is prospectively related to disease. One might also expect that sickness absence would be another consequence but very little data seem to exist. The present study used 8300 individuals in a national sample to obtain information on reports of disturbed sleep and fatigue 1 year and merged this with data on long-term sickness absence 2 years later. A logistic regression analysis was applied to the data with adjustments for demographic and work environment variables. The results showed that individuals without registered sickness absence at the start had a higher probability of entering a period of long-term (>/=90 days, odds ratio [OR] = 1.24 with 95% confidence interval [CI] = 1.02-1.51) sickness absence 2 years later if they reported disturbed sleep at the start. The figure for fatigue was OR = 1.35 (CI = 1.14-1.60). When fatigue or disturbed sleep was separately excluded the OR increased to OR = 1.44 and OR = 1.47, respectively. Intermediate sickness absence (14-89 days) showed similar but slightly weaker results. The results indicate that disturbed sleep and fatigue are predictors of long-term absence and it is suggested that impaired sleep may be part of a chain of causation, considering its effects on fatigue.PMID: 18036078 [PubMed - in process]
  • Anund, Anna, et al. (författare)
  • Driver impairment at night and its relation to physiological sleepiness.
  • 2008
  • Ingår i: Scand J Work Environ Health. - 0355-3140 .- 1795-990X. ; 34:2, s. 142-50
  • Tidskriftsartikel (refereegranskat)abstract
    • Driver impairment at night and its relation to physiological sleepiness.Anund A, Kecklund G, Peters B, Forsman A, Lowden A, Akerstedt T.VTI, S-581 95 Linköping, Sweden. anna.anund@vti.se.OBJECTIVES: Studies of devices detecting sleepiness need reference points of physiological sleepiness. The present study sought to validate the Karolinska drowsiness score (KDS) as an indicator of physiological sleepiness against driving impairment and eye blink duration during a 45-minute drive in an advanced moving-base driving simulator. METHODS: Data from 19 persons were used in the analysis. Electrooculography, electroencephalography, and electromyography were administered continuously. Physiological sleepiness was quantified by scoring the percentage (0-100%) of the scoring epoch with alpha and theta activity and slow eye movements (KDS). Lateral position and speed were used as measures of driving behavior. Lane departure was defined as two wheels touching the lane markers. Blink duration was used as a secondary indicator of sleepiness. RESULTS: The results showed that, for young drivers, sleepiness increased with time in the task with higher levels. The variability of the lateral position and the mean and variability of the blink duration significantly changed when sleepiness increased to KDS >/=20%. Furthermore, there was an increase in the risk of lane departure for KDS >/=30%. CONCLUSIONS: The results suggest that KDS scoring is a reasonable procedure for estimating physiological sleepiness under conditions of driving. The results also indicate that a younger age is associated with greater sensitivity to sleepiness at the wheel.
  • Arendt, Josephine, et al. (författare)
  • Clinical update : melatonin and sleep disorders.
  • 2008
  • Ingår i: Clin Med. - 1470-2118. ; 8:4, s. 381-3
  • Tidskriftsartikel (refereegranskat)abstract
    • Clinical update: melatonin and sleep disorders.Arendt J, Van Someren EJ, Appleton R, Skene DJ, Akerstedt T.Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford. j.arendt@surrey.ac.ukThe hormone melatonin is increasingly used for the treatment of certain sleep disorders, particularly those related to disturbed biological rhythms. This article summarises current knowledge of its mechanism of action and identifies situations where there is good evidence for its efficacy. The authors provide advice, based on their own experience and consistent published data, concerning the dose range of melatonin to be used and the critically important question of the timing of treatment. Anecdotal evidence for the use of melatonin needs to be replaced by data from well-controlled, preferably multi-centre, randomised clinical trials.
  • 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.
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