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| 2. |
- Akerstedt, Torbjörn, et al.
(författare)
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Accounting for partial sleep deprivation and cumulative sleepiness in the Three-Process Model of alertness regulation.
- 2008
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Ingår i: Chronobiol Int. - : Informa UK Limited. - 1525-6073 .- 0742-0528. ; 25:2, s. 309-19
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Tidskriftsartikel (refereegranskat)abstract
- Accounting for partial sleep deprivation and cumulative sleepiness in the Three-Process Model of alertness regulation.Akerstedt T, Ingre M, Kecklund G, Folkard S, Axelsson J.Stress Research Institute, University of Stockholm, Stockholm, Sweden. torbjorn.akerstedt@ki.seMathematical models designed to predict alertness or performance have been developed primarily as tools for evaluating work and/or sleep-wake schedules that deviate from the traditional daytime orientation. In general, these models cope well with the acute changes resulting from an abnormal sleep but have difficulties handling sleep restriction across longer periods. The reason is that the function representing recovery is too steep--usually exponentially so--and with increasing sleep loss, the steepness increases, resulting in too rapid recovery. The present study focused on refining the Three-Process Model of alertness regulation. We used an experiment with 4 h of sleep/night (nine participants) that included subjective self-ratings of sleepiness every hour. To evaluate the model at the individual subject level, a set of mixed-effect regression analyses were performed using subjective sleepiness as the dependent variable. These mixed models estimate a fixed effect (group mean) and a random effect that accounts for heterogeneity between participants in the overall level of sleepiness (i.e., a random intercept). Using this technique, a point was sought on the exponential recovery function that would explain maximum variance in subjective sleepiness by switching to a linear function. The resulting point explaining the highest amount of variance was 12.2 on the 1-21 unit scale. It was concluded that the accumulation of sleep loss effects on subjective sleepiness may be accounted for by making the recovery function linear below a certain point on the otherwise exponential function.
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| 3. |
- Akerstedt, Torbjörn, et al.
(författare)
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Disturbed sleep in shift workers, day workers, and insomniacs.
- 2008
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Ingår i: Chronobiol Int. - : Informa UK Limited. - 1525-6073 .- 0742-0528. ; 25:2, s. 333-48
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Tidskriftsartikel (refereegranskat)abstract
- Disturbed sleep in shift workers, day workers, and insomniacs.Akerstedt T, Ingre M, Broman JE, Kecklund G.Stress Research Institute, University of Stockholm, Karolinska Institutet, Stockholm, Sweden. torbjorn.akerstedt@ki.seVery little is known about differences in sleep between day and shift workers in representative samples of the population. This study compared a national representative sample (N=3400) of shift (with night shifts) and day workers regarding the different types of sleep disturbances and also the level of sleep symptoms with that of insomnia patients. The results showed very few differences between shift and day workers; only "too little sleep" and "nodding off at work" were marginally higher among shift workers. The results also showed that the complaints of insomnia patients for most sleep disturbances corresponded to the 2nd-16th percentile of the shift workers' levels of complaints. The results suggest, at least with the present questionnaire methodology, that shift work does not appear to be a major source of sleep disturbances and that their complaint levels bear no resemblance to those seen in insomniac patients.
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| 4. |
- Akerstedt, Torbjörn, et al.
(författare)
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Effects of context on sleepiness self-ratings during repeated partial sleep deprivation.
- 2008
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Ingår i: Chronobiol Int. - : Informa UK Limited. - 1525-6073 .- 0742-0528. ; 25:2, s. 271-8
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Tidskriftsartikel (refereegranskat)abstract
- Effects of context on sleepiness self-ratings during repeated partial sleep deprivation.Akerstedt T, Kecklund G, Axelsson J.Stress Research Institute, Stockholm University, Stockholm, Sweden. torbjorn.akerstedt@ki.seRatings of subjective sleepiness are often used in laboratory and field studies of sleep loss and shifted sleep hours. Some studies suggest that such ratings might fail to reflect sleepiness as shown in physiology or performance. One reason for this may be the influence of the context of the rating. Social interaction or physical activity may mask latent sleepiness. The present study attempted to approach this question. Nine subjects participated in a partial sleep-deprivation experiment (five days of 4 h of time in bed [TIB]), preceded by two baseline days (8 h TIB) and followed by three recovery days (8 h TIB). Sleepiness was self-rated on the Karolinska Sleepiness Scale (KSS; scores of 1-9) after a period of relaxation, after a reaction-time test, and after 30 min of free activities. The results showed a strong increase in subjective sleepiness during sleep restriction and a significant difference between conditions. Free activity reduced the self-rated subjective sleepiness by 1.1 KSS units compared to the level of sleepiness self-rated at the end of the reaction-time test. Thus, the results of this study indicate that the context of a sleepiness rating affects the outcome of the rating.
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| 5. |
- Akerstedt, Torbjörn, et al.
(författare)
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Predicting road crashes from a mathematical model of alertness regulation--The Sleep/Wake Predictor.
- 2008
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Ingår i: Accid Anal Prev. - : Elsevier BV. - 0001-4575. ; 40:4, s. 1480-5
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Predicting road crashes from a mathematical model of alertness regulation--The Sleep/Wake Predictor.Akerstedt T, Connor J, Gray A, Kecklund G.Stress Research Institute, Stockholm University and Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden. torbjorn.akerstedt@ki.seSleepiness is related to factors such as the time of day, the time since awakening and the duration of prior sleep. The present study investigated whether actual road crashes could be predicted from a mathematical model based on these three factors (the Sleep/Wake Predictor-SWP). Data were derived from a population-based case-control study of serious injury crashes. Data on accident time (or control sampling time) and start and end of prior sleep were entered into the model (blind). The predicted sleepiness values were used in logistic regressions. The results showed a highly significant odds ratio (OR)=1.72 (confidence interval=1.41-2.09) for each incremental step of sleepiness on the output sleepiness scale (nine steps). There was also a significant interaction with blood alcohol level, showing high OR values for high sleepiness levels and alcohol levels above 50 mg% (0.05 g/dl). It was concluded that the model is a good predictor of road crashes beyond that of alcohol level, and that interaction between the two carries a very high risk.
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| 6. |
- Akerstedt, Torbjörn, et al.
(författare)
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Sleep and sleepiness in relation to stress and displaced work hours.
- 2007
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Ingår i: Physiol Behav. - : Elsevier BV. - 0031-9384. ; 92:1-2, s. 250-5
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Sleep and sleepiness in relation to stress and displaced work hours.Akerstedt T, Kecklund G, Gillberg M.Karolinska Institutet, Institute for Psychosocial Medicine Box 230, S-171 77 Stockholm, Sweden. torbjorn.akerstedt@ipm.ki.seSleep is an important factor in relation to accidents, long-term health and mortality. Our group has had a long-term commitment to research on sleep regulation and its consequences. Over the years we have demonstrated pronounced effects of night work on sleep and alertness, including electroencephalographically determined sleep during work. We have also demonstrated that experimental displacement of sleep will result in short sleep at daytime and increased physiological sleepiness at night and developed mathematical models for prediction of sleep duration, as well as of sleepiness and risk of sleep-related accidents. We have also looked at the concept of sleep quality and found it dependent on sleep duration, sleep continuity and content of sleep stages 3 and 4. Sleep is also clearly disturbed in patients on long-term sick leave for burnout or in non-patients with high burnout scores, in particular sleep fragmentation is increased and sleep efficiency and sleep stages 3 and 4 (SWS--deep sleep) decreased. The fragmentation in turn seems related to endocrine changes. Present work is focused on bringing this work together, connecting the links from stress to sleep to metabolic changes to disease and long-term sickness absence.PMID: 17585960 [PubMed - indexed for MEDLINE]
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| 7. |
- Akerstedt, Torbjörn, et al.
(författare)
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Sleep homeostasis during repeated sleep restriction and recovery : support from EEG dynamics.
- 2009
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Ingår i: Sleep. - : Oxford University Press (OUP). - 0161-8105 .- 1550-9109. ; 32:2, s. 217-22
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Tidskriftsartikel (refereegranskat)abstract
- STUDY OBJECTIVES: Sleep reduction normally causes a homeostatic response during subsequent recovery sleep, but this does not seem to be true for repeated partial sleep loss. The aim of the present study was to test the response to repeated partial sleep loss through detailed focus on spectral data and parts of sleep. DESIGN: The experiment involved 4 h of sleep across 5 days in the laboratory (partial sleep deprivation [PSD]), followed by 3 days of recovery sleep. PSD was achieved through a delayed bedtime. Nine individuals participated. To avoid "laboratory monotony," subjects were permitted to leave the lab for a few hours each day. MEASUREMENTS AND RESULTS: All sleep stages and the latencies to sleep and slow wave sleep (SWS) showed a significant reduction during PSD. However, SWS and TST (total sleep time) during the first half of sleep increased gradually across days with PSD. During the first recovery sleep, SWS was significantly increased, while stage 1 and latency to stage 3 were reduced. All were back to baseline on the second night of recovery sleep. Summed spectral power during the first 3.8 h of sleep showed a gradual and robust increase (50% above baseline) in the range 1.25-7.25 Hz across days with PSD up to first recovery sleep and then returned to baseline. CONCLUSIONS: SWS and summed power density in a broad low-frequency band respond to repeated partial sleep deprivation in a dose-response fashion during the first 4 h sleep, apparently reflecting a robust and stable homeostatic response to sleep loss.
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| 8. |
- Anund, Anna, et al.
(författare)
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Driver sleepiness and individual differences in preferences for countermeasures.
- 2008
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Ingår i: J Sleep Res. - : Wiley. - 1365-2869 .- 0962-1105. ; 17:1, s. 16-22
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- 1: J Sleep Res. 2008 Mar;17(1):16-22. LinksDriver sleepiness and individual differences in preferences for countermeasures.Anund A, Kecklund G, Peters B, Akerstedt T.Swedish National Road and Transport Research Institute (VTI), Linköping, Sweden. anna.anund@vti.seThe aim of the present national questionnaire study was to relate the use of sleepiness countermeasures among drivers to possible explanatory factors such as age, sex, education, professional driving, being a shift worker, having experience of sleepy driving, sleep-related crashes, problems with sleep and sleepiness in general and sleep length during working days. Also the attitude to countermeasures related to information or driver support system was studied. A random sample of 3041 persons was drawn from the national register of vehicle owners. The response rate was 62%. The most common countermeasures were to stop to take a walk (54%), turn on the radio/stereo (52%), open a window (47%), drink coffee (45%) and to ask passengers to engage in conversation (35%). Logistic regression analysis showed that counteracting sleepiness with a nap (a presumably efficient method) was practiced by those with experience of sleep-related crashes or of driving during severe sleepiness, as well as by professional drivers, males and drivers aged 46-64 years. The most endorsed means of information to the driver about sleepiness was in-car monitoring of driving performance providing drivers with information on bad or unsafe driving. This preference was related to experience of sleepy driving, not being a professional driver and male gender. Four clusters of behaviours were identified: alertness-enhancing activity while driving (A), stopping the car (S), taking a nap (N) and ingesting coffee or other sources of caffeine (C) (energy drinks, caffeine tablets). The participants were grouped according to their use of any of the four categories of countermeasures. The most common cluster was those who used activity, as well as stopping and drinking caffeine.PMID: 18275551 [PubMed - in process]
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| 9. |
- Anund, Anna, et al.
(författare)
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The alerting effect of hitting a rumble strip--a simulator study with sleepy drivers.
- 2008
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Ingår i: Accid Anal Prev. - : Elsevier BV. - 1879-2057 .- 0001-4575. ; 40:6, s. 1970-6
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Tidskriftsartikel (refereegranskat)abstract
- The alerting effect of hitting a rumble strip--a simulator study with sleepy drivers.Anund A, Kecklund G, Vadeby A, Hjälmdahl M, Akerstedt T.Clinical Neuroscience, Karolinska Institutet, SE-177 71 Stockholm, Sweden. anna.anund@vti.seA moving base driving simulator experiment was carried out in order to investigate the effects of milled rumble strips on driver fatigue. There were rumble strips both at the edge line and centre line. Four different physical designs of milled rumble strips (yielding noise values from 1.5 to 16 dBA) and two placements on shoulder were used in the experiment. Sound and vibrations from real milled rumble strips were reproduced in the simulator. In total 35 regular shift workers drove during the morning hours after a full night shift. The main results showed an increase in sleepiness indicators (EEG alpha/theta activity, eye closure duration, standard deviation of lateral position, subjective sleepiness) from start to before hitting the rumble strip, an alerting effect in most parameters (not subjective sleepiness) after hitting the strip. The alertness enhancing effect was, however, short and the sleepiness signs returned 5 min after the rumble strip hit. Essentially no effects were seen due to type of strip. It was concluded that various aspects of sleepiness are increased before hitting a rumble strip and that the effect is very short-lived. Type of strip, as used in the present study did not have any effect.
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| 10. |
- Asberg, Marie, et al.
(författare)
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Novel biochemical markers of psychosocial stress in women.
- 2009
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Prolonged psychosocial stress is a condition assessed through self-reports. Here we aimed to identify biochemical markers for screening and early intervention in women. METHODS: Plasma concentrations of interleukin (IL) 1-alpha, IL1-beta, IL-2, IL-4, IL-6, IL-8, IL-10, interferon-gamma (INF-gamma), tumor necrosis factor-alpha (TNF-alpha), monocyte chemotactic protein-1 (MCP-1), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), thyroid stimulating hormone (TSH), total tri-iodothyronine (TT3), total thyroxine (TT4), prolactin, and testosterone were measured in: 195 women on long-term sick-leave for a stress-related affective disorder, 45 women at risk for professional burnout, and 84 healthy women. RESULTS: We found significantly increased levels of MCP-1, VEGF and EGF in women exposed to prolonged psychosocial stress. Statistical analysis indicates that they independently associate with a significant risk for being classified as ill. CONCLUSIONS: MCP-1, EGF, and VEGF are potential markers for screening and early intervention in women under prolonged psychosocial stress.
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