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Sökning: WFRF:(Akerstedt Torbjorn)

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1.
  • Ahlstrom, C, et al. (författare)
  • The impact of driver sleepiness on fixation-related brain potentials
  • 2019
  • Ingår i: Journal of Sleep Research. - 1365-2869 .- 0962-1105.
  • 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.
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2.
  • Persson, Roger, et al. (författare)
  • Impact of an 84-hour workweek on biomarkers for stress, metabolic processes and diurnal rhythm
  • 2006
  • Ingår i: Scandinavian Journal of Work, Environment and Health. - Finnish Institute of Occupational Health. - 0355-3140. ; 32:5, s. 349-358
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives This study examined the degree to which long workhours in combination with an extended workweek (12 hours/7 days) with permanent day shifts (0700-1900), as requested by the workers, influenced biomarkers for stress, metabolic processes, and diurnal rhythm. Methods Construction workers (N=50) working 84 hours a week, with alternate weeks off, were compared with construction workers (N=25) having a traditional 40-hour work schedule. The participants were all male and between the ages of 21 to 65 years. Blood samples were obtained in the morning immediately prior to the start of work on workday 1, 5, and 7 to assess cholesterol, cortisol, dehydroepiandrosterone, melatonin, prolactin, testosterone, and uric acid. Psychosocial circumstances were assessed with a questionnaire. Results The 84-hour group had higher melatonin concentrations and reported higher job-control scores than the 40-hour group. For both groups, the melatonin, cortisol, and cholesterol concentrations were lower on workday 5 than on workday 1. In the 84-hour group, most of the biomarkers were significantly lower in concentrations on workday 7 than on workday 1. Only testosterone showed a significant decrease between workdays 5 and 7. The concentrations of dehydroepiandrosterone and uric acid remained stable across all of the days, as did the melatonin concentrations between workdays 5 and 7. Conclusions Working of one's own freewill on an 84-hour regimen is not, in the short-term, necessarily more harmful for health than working on a 40-hour regimen with a similar type of heavy worktasks. However, working on an 84-hour schedule beyond the ordinary 40-hour week results in signs of a functional shift in hormonal regulation.
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3.
  • Ahlstrom, Christer, et al. (författare)
  • The effect of daylight versus darkness on driver sleepiness: a driving simulator study
  • 2018
  • Ingår i: Journal of Sleep Research. - WILEY. - 0962-1105 .- 1365-2869. ; 27:3
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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 +/- 1.7years old) participated in a driving simulator experiment where they drove on a rural road. A 2x2 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.</p>
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4.
  • 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 : Emerging Technologies. - Elsevier. - 0968-090X .- 1879-2359. ; 26, s. 20-32
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
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5.
  • Ahlström, 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.. - 0962-1105 .- 1365-2869.
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
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6.
  • 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
    • <p>Predicting long-term sickness absence from sleep and fatigue.</p><p>Akerstedt T, Kecklund G, Alfredsson L, Selen J.</p><p>Institute for Psychosocial Medicine, Public Health Sciences, Karolinska Institutet, Stockholm, Sweden. torbjorn.akerstedt@ipm.ki.se</p><p>Disturbed 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 (&gt;/=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.</p><p>PMID: 18036078 [PubMed - in process]</p>
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7.
  • Akerstedt, Torbjorn, et al. (författare)
  • Women with both sleep problems and snoring show objective impairment of sleep
  • 2018
  • Ingår i: Sleep Medicine. - 1389-9457 .- 1878-5506. ; 51, s. 80-84
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Objective: Combined insomnia and obstructive sleep apnea has been the focus of considerable research with respect to its health effects. A related issue is whether sleep disturbances in combination with snoring might exert effects on objective sleep variables in the non-clinical general population. The purpose of the present study was to investigate the polysomnographical characteristics of individuals who had sought medical help for both disturbed sleep and for snoring. No previous work of this type has been carried out. Method: For this study we used a representative set of data of 384 women with one night of in-home PSG. We identified those individuals who had sought medical help for sleep problems (SL), individuals that had sought help for snoring (SN), as well as those that had sought help for either both (Combined), or for neither (Control). Results: Our results yielded an N of 46, 16, 21, and 301 individuals, respectively. A one-factor analysis of variance showed significant main effects on N1% (F = 10.2, p &lt; 0.001), N3% (F = 2.7, p &lt; 0.05), AHI/h (F = 5.5, p &lt; 0.001), and a delta power measure (F = 3.8, p &lt; 0.05). The combined group showed significantly higher levels than the other groups for N1% (29% vs &lt; 21%), AHI/h (19/h vs &lt; 10/h) and lower levels for N3%, and a measure of delta power. Reported sleep quality measures did not show the same pattern, since the highest/lowest value were found for either the group presenting snoring alone or sleep problems alone. Conclusion: We concluded that individuals who had sought help for both insomnia and snoring showed impaired sleep in terms of PSG and that this was not reflected in ratings of sleep or health. This suggests that simultaneous sleep disturbances and snoring may potentiate each other to cause impaired sleep, yet the mechanism still needs to be elucidated.</p>
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8.
  • Anund, Anna, et al. (författare)
  • Driver impairment at night and its relation to physiological sleepiness
  • 2008
  • Ingår i: Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 34:2, s. 142-150
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
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9.
  • 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
    • <p>Clinical update: melatonin and sleep disorders.</p><p>Arendt J, Van Someren EJ, Appleton R, Skene DJ, Akerstedt T.</p><p>Centre for Chronobiology, Faculty of Health and Medical Sciences, University of Surrey, Guildford. j.arendt@surrey.ac.uk</p><p>The 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.</p>
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10.
  • 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
    • <p>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 90 min 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 5 min (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.</p>
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