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  • 1. Ahlström, Christer
    et al.
    Anund, Anna
    Fors, Carina
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    The effect of daylight versus darkness on driver sleepiness: a driving simulator study2018Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 27, nr 3, artikkel-id e12642Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 2. Ahlström, Christer
    et al.
    Solis-Marcos, Ignacio
    Nilsson, Emma
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    The impact of driver sleepiness on fixation-related brain potentials2020Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 29, nr 5, artikkel-id e12962Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 3.
    Balter, Leonie J. T.
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Stockholm, Sweden.
    Sundelin, Tina
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Stockholm, Sweden.
    Holding, Benjamin C.
    Petrovic, Predrag
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet Stockholm Sweden.
    Intelligence predicts better cognitive performance after normal sleep but larger vulnerability to sleep deprivation2023Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 32, nr 4, artikkel-id e13815Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fluid intelligence is seen as a beneficial attribute, protecting against stress and ill-health. Whether intelligence provides resilience to the cognitive effects of insufficient sleep was tested in the current pre-registered experimental study. Participants (N = 182) completed the Raven's test (measuring fluid intelligence) and a normal night of sleep or a night of total sleep deprivation. Sleepiness and four cognitive tests were completed at 22:30 hours (baseline), and the following day after sleep manipulation. At baseline, higher fluid intelligence was associated with faster and more accurate arithmetic calculations, and better episodic memory, but not with spatial working memory, simple attention or sleepiness. Those with higher fluid intelligence were more, not less, impacted by sleep deprivation, evident for arithmetic ability, episodic memory and spatial working memory. We need to establish a more nuanced picture of the benefits of intelligence, where intelligence is not related to cognitive advantages in all situations.

  • 4. Brandão, Luiz Eduardo Mateus
    et al.
    Espes, Daniel
    Orzechowski Westholm, Jakub
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik. Stockholms universitet, Science for Life Laboratory (SciLifeLab).
    Martikainen, Teemu
    Westerlund, Nestori
    Lampola, Lauri
    Popa, Alexandru
    Vogel, Heike
    Schürmann, Annette
    Dickson, Suzanne L.
    Benedict, Christian
    Cedernaes, Jonathan
    Acute sleep loss alters circulating fibroblast growth factor 21 levels in humans: A randomised crossover trial2022Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 31, nr 2, artikkel-id e13472Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hormone fibroblast growth factor 21 (FGF21) modulates tissue metabolism and circulates at higher levels in metabolic conditions associated with chronic sleep–wake disruption, such as type 2 diabetes and obesity. In the present study, we investigated whether acute sleep loss impacts circulating levels of FGF21 and tissue-specific production, and response pathways linked to FGF21. A total of 15 healthy normal-weight young men participated in a randomised crossover study with two conditions, sleep loss versus an 8.5-hr sleep window. The evening before each intervention, fasting blood was collected. Fasting, post-intervention morning skeletal muscle and adipose tissue samples underwent quantitative polymerase chain reaction and DNA methylation analyses, and serum FGF21 levels were measured before and after an oral glucose tolerance test. Serum levels of FGF21 were higher after sleep loss compared with sleep, both under fasting conditions and following glucose intake (~27%–30%, p = 0.023). Fasting circulating levels of fibroblast activation protein, a protein which can degrade circulating FGF21, were not altered by sleep loss, whereas DNA methylation in the FGF21 promoter region increased only in adipose tissue. However, even though specifically the muscle exhibited transcriptional changes indicating adverse alterations to redox and metabolic homeostasis, no tissue-based changes were observed in expression of FGF21, its receptors, or selected signalling targets, in response to sleep loss. In summary, we found that acute sleep loss resulted in increased circulating levels of FGF21 in healthy young men, which may occur independent of a tissue-based stress response in metabolic peripheral tissues. Further studies may decipher whether changes in FGF21 signalling after sleep loss modulate metabolic outcomes associated with sleep or circadian disruption.

  • 5. Conte, Francesca
    et al.
    De Rosa, Oreste
    Rescott, Marissa Lynn
    Arabia, Teresa Pia
    D'Onofrio, Paolo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Lustro, Alessio
    Malloggi, Serena
    Molinaro, Danila
    Spagnoli, Paola
    Giganti, Fiorenza
    Barbato, Giuseppe
    Ficca, Gianluca
    High sleep fragmentation parallels poor subjective sleep quality during the third wave of the Covid-19 pandemic: An actigraphic study2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, artikkel-id e13519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies on sleep during the Covid-19 pandemic have mostly been conducted during the first wave of contagion (spring 2020). To follow up on two Italian studies addressing subjective sleep features during the second wave (autumn 2020), here we assess sleep during the third wave (spring 2021) in a sample of healthy adults from Campania (Southern Italy). Actigraphic data (on 2 nights) and the Pittsburgh Sleep Quality Index were collected from 82 participants (40 F, mean age: 32.5 +/- 11.5 years) from 11 March to 18 April 2021, when Campania was classified as a red zone, i.e. it was subjected to strict restrictions, only slightly looser than those characterizing the first national lockdown (spring 2020). Although objective sleep duration and architecture appeared in the normal range, the presence of disrupted sleep was indexed by a relevant degree of sleep fragmentation (number of awakenings >= 1 min: 12.7 +/- 6.12; number of awakenings >= 5 min: 3.04 +/- 1.52), paralleled by poor subjective sleep quality (Pittsburgh Sleep Quality Index global score: 5.77 +/- 2.58). These data suggest that the relevant subjective sleep impairments reported during the first wave could have relied on subtle sleep disruptions that were undetected by the few objective sleep studies from the same period. Taken together with sleep data on previous phases of the pandemic, our findings show that the detrimental effects on sleep determined by the initial pandemic outbreak have not abated across the subsequent waves of contagion, and highlight the need for interventions addressing sleep health in global emergencies.

  • 6. Filtness, Ashleigh J.
    et al.
    Anund, Anna
    Fors, Carina
    Ahlström, Christer
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Radboud University Nijmegen, Netherlands.
    Sleep-related eye symptoms and their potential for identifying driver sleepiness2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr 5, s. 568-575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The majority of individuals appear to have insight into their own sleepiness, but there is some evidence that this does not hold true for all, for example treated patients with obstructive sleep apnoea. Identification of sleep-related symptoms may help drivers determine their sleepiness, eye symptoms in particular show promise. Sixteen participants completed four motorway drives on two separate occasions. Drives were completed during daytime and night-time in both a driving simulator and on the real road. Ten eye symptoms were rated at the end of each drive, and compared with driving performance and subjective and objective sleep metrics recorded during driving. 'Eye strain', 'difficulty focusing', 'heavy eyelids' and 'difficulty keeping the eyes open' were identified as the four key sleep-related eye symptoms. Drives resulting in these eye symptoms were more likely to have high subjective sleepiness and more line crossings than drives where similar eye discomfort was not reported. Furthermore, drivers having unintentional line crossings were likely to have 'heavy eyelids' and 'difficulty keeping the eyes open'. Results suggest that drivers struggling to identify sleepiness could be assisted with the advice 'stop driving if you feel sleepy and/or have heavy eyelids or difficulty keeping your eyes open'.

  • 7.
    Garefelt, Johanna
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Gershagen, Sara
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Westerlund, Hugo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Platts, Loretta G.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    How does work impact daily sleep quality? A within-individual study using actigraphy and self-reports over the retirement transition2022Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 31, nr 3, artikkel-id e13513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study examined how the cessation of work at retirement affects daily measures of actigraphy-measured and self-rated sleep quality. Time in bed or asleep and stress at bedtime were examined as potential mechanisms. In total 117 employed participants who were aged 60-72 years and planned to retire soon were recruited to the Swedish Retirement Study. Sleep quality was measured in a baseline week using accelerometers, diaries, and questionnaires. Subjective sleep measures were sleep quality, restless sleep, restorative sleep, getting enough sleep, estimated wake after sleep onset, difficulties falling asleep, too early final awakening, and difficulties waking up. Actigraphy measures were sleep efficiency, wake after sleep onset, and average awakening length. After 1 and 2 years, the measurements were repeated for the now retired participants. Daily variations in sleep quality before and after retirement were analysed using multilevel modelling, with time in bed or asleep and stress at bedtime as potential mediators. We found that several self-reports of sleep improved (e.g., +0.2 standard deviations for sleep quality and +0.5 standard deviations for restorative sleep) while objective sleep quality remained unchanged or decreased slightly with retirement (e.g., -0.8% for sleep efficiency). Increased time in bed or asleep and stress at bedtime accounted partially for the improvements in self-rated sleep quality at retirement. In conclusion, actigraph-measured and self-reported sleep quality do not change in concert at retirement, highlighting the interest of studying both outcomes. The main effects of retirement from work concern subjective experiences of recovery more than sleep quality per se.

  • 8.
    Garefelt, Johanna
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Platts, Loretta G.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Hyde, Martin
    Magnusson Hanson, Linda L.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Westerlund, Hugo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Reciprocal relations between work stress and insomnia symptoms: A prospective study2020Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 29, nr 2, artikkel-id e12949Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Work stress and poor sleep are closely related in cross-sectional data, but evidence from prospective data is limited. We analysed how perceived stress and work stressors (work demands, decision authority and workplace social support) are related to key dimensions of insomnia over time, using structural equation modelling. Biennial measurements from a large sample of the working population in Sweden enabled us to analyse both the relationship from stress to sleep as well as that from sleep to stress. Overall, we found reciprocal relations between insomnia and all four stress measures. However, looking at the relation between each dimension of insomnia and each stress measure, there were some differences in direction of effects. In the direction from stress to sleep, all work stressors as well as perceived stress predicted both difficulties initiating sleep and difficulties maintaining sleep. The same was found for non-restorative sleep, with the exception for decision authority. In the opposite direction, difficulties maintaining sleep predicted increased levels of work demands and perceived stress. Difficulties initiating sleep stood out among the insomnia symptoms as not predicting any of the stress measures, while non-restorative sleep was the only symptom predicting all stress measures. The results advance the understanding of the stress-sleep relationship and indicate a potential vicious circle between insomnia and perceived stress as well as work stressors, suggesting that the workplace could be an arena for interventions to alleviate insomnia.

  • 9.
    Garefelt, Johanna
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Westerlund, Hugo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Magnusson Hanson, Linda L.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Sverke, Magnus
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Work and sleep – a prospective study of psychosocial work factors, physical work factors and work scheduling2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr S1, s. 218-218, artikkel-id P706Artikkel i tidsskrift (Fagfellevurdert)
  • 10.
    Garefelt, Johnna
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Gershagen, Sara
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Westerlund, Hugo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Platts, Loretta
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    How does cessation of work affect sleep? Prospective analyses of sleep duration, timing and efficiency from the Swedish Retirement Study2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 3, artikkel-id e13157Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several strands of research indicate that work competes for time with sleep, but to what extent the timing and duration of sleep is affected by work is not known. Retirement offers a quasi-experimental life transition to study this in a within-individual study design. The few existing studies report that people sleep longer and later after retirement but mainly rely on self-reported data or between-individual analyses. We recruited 100 participants aged 61–72 years who were in paid work but would soon retire and measured them in a baseline week with accelerometers, diaries and questionnaires. After 1 and 2 years, the measurements were repeated for the now retired participants. Changes in sleep duration, timing, efficiency, chronotype and social jetlag were analysed using multilevel modelling. Gender, chronotype at baseline and partner's working status were analysed as potential effect modifiers. Sleep duration increased by 21 min, whereas sleep efficiency remained similar. Time of sleep onset and final awakening were postponed by 26 and 52 min, respectively, pushing midsleep forward from 03:17 to 03:37 hours. Changes in duration and timing of sleep were driven by weekday sleep, whereas weekend sleep stayed about the same. Social jetlag decreased but still occurred after retirement. Changes at retirement in sleep duration and timing were smaller for participants with a later chronotype and who had full-time working partners. These findings indicate that paid work generates sleep loss and hinders people from sleeping in line with their biological time.

  • 11.
    Gerhardsson, Andreas
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Porada, Danja K.
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Lundström, Johan N.
    Stockholms universitet, Humanistiska fakulteten, Institutionen för lingvistik. Karolinska Institute, Sweden; Monell Chemical Senses Center, USA; University of Pennsylvania, USA.
    Schwarz, Johanna
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Does insufficient sleep affect how you learn from reward or punishment? Reinforcement learning after 2 nights of sleep restriction2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 4, artikkel-id e13236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To learn from feedback (trial and error) is essential for all species. Insufficient sleep has been found to reduce the sensitivity to feedback as well as increase reward sensitivity. To determine whether insufficient sleep alters learning from positive and negative feedback, healthy participants (n = 32, mean age 29.0 years, 18 women) were tested once after normal sleep (8 hr time in bed for 2 nights) and once after 2 nights of sleep restriction (4 hr/night) on a probabilistic selection task where learning behaviour was evaluated in three ways: as generalised learning, short-term win-stay/lose-shift learning strategies, and trial-by-trial learning rate. Sleep restriction did not alter the sensitivity to either positive or negative feedback on generalised learning. Also, short-term win-stay/lose-shift strategies were not affected by sleep restriction. Similarly, results from computational models that assess the trial-by-trial update of stimuli value demonstrated no difference between sleep conditions after the first block. However, a slower learning rate from negative feedback when evaluating all learning blocks was found after sleep restriction. Despite a marked increase in sleepiness and slowed learning rate for negative feedback, sleep restriction did not appear to alter strategies and generalisation of learning from positive or negative feedback.

  • 12.
    Gerhardsson, Andreas
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Fischer, Håkan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Lekander, Mats
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Schwarz, Johanna
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Effect of sleep deprivation on emotional working memory2019Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 28, nr 1, artikkel-id e12744Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The emotional dysregulation and impaired working memory found after sleep loss can have severe implications for our daily functioning. Considering the intertwined relationship between emotion and cognition in stimuli processing, there could be further implications of sleep deprivation in high‐complex emotional situations. Although studied separately, this interaction between emotion and cognitive processes has been neglected in sleep research. The aim of the present study was to investigate the effect of 1 night of sleep deprivation on emotional working memory. Sixty‐one healthy participants (mean age: 23.4 years) were either sleep deprived for 1 night (n = 30) or had a normal night’s sleep (n = 31). They performed an N‐back task with two levels of working memory load (1‐back and 3‐back) using positive, neutral and negative picture scenes. Sleep deprivation, compared with full night sleep, impaired emotional working memory accuracy, but not reaction times. The sleep‐deprived participants, but not the controls, responded faster to positive than to negative and neutral pictures. The effect of sleep deprivation was similar for both high and low working memory loads. The results showed that although detrimental in terms of accuracy, sleep deprivation did not impair working memory speed. In fact, our findings indicate that positive stimuli may facilitate working memory processing speed after sleep deprivation.

  • 13. Ghilotti, Francesca
    et al.
    Bellocco, Rino
    Trolle Lagerros, Ylva
    Thorson, Anna
    Theorell-Haglöw, Jenny
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Lindberg, Eva
    Relationship between sleep characteristics and markers of inflammation in Swedish women from the general population2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 2, artikkel-id e13093Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Systemic inflammation is thought to mediate the link between sleep and cardiovascular outcomes, but previous studies on sleep habits and inflammation markers have found inconsistent results. This study investigated the relationship between sleep characteristics and C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha). A representative sample of 319 Swedish women was randomly selected from the general population for in-home polysomnography, sleep questionnaire and blood samples. As variables were highly correlated, principal component analysis was used to reduce the number of original variables. Linear regression with log-transformation of the outcomes (lnCRP, lnIL-6 and lnTNF alpha) and quantile regression were fitted to estimate cross-sectional relationships. Multivariable linear regression models suggested a significant association of insomnia symptoms (self-reported) with higher lnCRP levels (beta = 0.11; 95% confidence interval [CI] = 0.02; 0.21), but not with lnIL-6 and lnTNF alpha. From quantile regression analysis we found that a high non-restorative index (subjective) and insomnia symptoms (self-reported) were associated with higher values of CRP, especially in the highest quantiles of the CRP distribution (90th percentile: beta = 0.71; 95% CI = 0.17; 1.24. beta = 1.23; 95% CI = 0.44; 2.02, respectively). Additionally, higher amounts of rapid eye movement (REM) sleep were associated with lower CRP values (90th percentile: beta = -0.80; 95% CI = -0.14; -1.46). In conclusion, sleep disturbances (self-reported), specifically difficulties maintaining sleep and early morning awakenings, but not sleep duration (neither subjective nor objective), were associated with higher CRP levels. No association was found with IL-6 or TNF alpha. Elevated REM sleep was associated with lower CRP levels. The results suggest that inflammation might be an intermediate mechanism linking sleep and health in women.

  • 14. Hedström, Anna Karin
    et al.
    Hössjer, Ola
    Stockholms universitet, Naturvetenskapliga fakulteten, Matematiska institutionen.
    Trolle Lagerros, Ylva
    Åkerstedt, Torbjorn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Short- and long-term mortality following hypnotic use2020Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 29, nr 4, artikkel-id e13061Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Potential long-term consequences of hypnotics remain controversial. We used the prospective Swedish National March Cohort, a study based on 41,695 participants with a mean follow-up duration of 18.9 years. Logistic regression models and Cox proportional hazards models with attained age as timescale were used to assess associations of hypnotic use with short- and long-term mortality. The proportion of subjects who initiated or discontinued hypnotic use during follow-up was substantial. All groups of hypnotics were associated with increased mortality within 2 years after a first prescription, with an overall OR of 2.38 (95% CI, 2.13-2.66). The association was more pronounced among subjects younger than 60 years (OR, 6.16; 95% CI, 3.98-9.52). There was no association between hypnotic use and long-term mortality. The association between hypnotic use and increased mortality was thus restricted to a relatively short period after treatment initiation, and may be explained in terms of confounding by indication.

  • 15.
    Heming, Meike
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Xu, Tianwei
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Nyberg, Anna
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Uppsala University, Sweden.
    Magnusson Hanson, Linda L.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    The relationship between onset of workplace violence and onset of sleep disturbances in the Swedish working population2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 5, artikkel-id e13307Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The study investigated the association between onset of workplace violence and onset of sleep disturbances. We used self-reported data from the Swedish Longitudinal Occupational Survey of Health (SLOSH) collected in 2014, 2016, and 2018. A two-wave design was based on participants who had no exposure to workplace violence or sleep disturbances at baseline (n = 6,928). A three-wave design was based on participants who in addition were unexposed to sleep disturbances in the second wave (n = 6,150). Four items of the Karolinska Sleep Questionnaire were used to measure sleep disturbances and one question was used to measure the occurrence of workplace violence or threats of violence. Multivariate logistic regression analyses were performed. In the two-wave approach, onset of workplace violence was associated with onset of sleep disturbances after adjustment for sex, age, occupational position, education, and civil status (adjusted odds ratio 1.41, 95% confidence interval 1.02-1.96). The association was no longer statistically significant after further adjustment for night/evening work, demands, control, and social support at work. In the three-wave approach, results were only suggestive of an association between onset of workplace violence and subsequent onset of sleep disturbances after adjustment for sex, age, occupational position, education, and civil status. Onset of frequent exposure to workplace violence was associated with subsequent onset of sleep disturbances in the adjusted analyses, but these analyses were based on few individuals (13 exposed versus 5,907 unexposed). The results did not conclusively demonstrate that onset of workplace violence predicts development of sleep disturbances. Further research could elucidate the role of other working conditions.

  • 16. Holding, Benjamin C.
    et al.
    Sundelin, Tina
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden; New York University, NY, USA.
    Cairns, Patrick
    Perrett, David I.
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    The effect of sleep deprivation on objective and subjective measures of facial appearance2019Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 28, nr 6, artikkel-id e12860Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The faces of people who are sleep deprived are perceived by others as looking paler, less healthy and less attractive compared to when well rested. However, there is little research using objective measures to investigate sleep-loss-related changes in facial appearance. We aimed to assess the effects of sleep deprivation on skin colour, eye openness, mouth curvature and periorbital darkness using objective measures, as well as to replicate previous findings for subjective ratings. We also investigated the extent to which these facial features predicted ratings of fatigue by others and could be used to classify the sleep condition of the person. Subjects (n = 181) were randomised to one night of total sleep deprivation or a night of normal sleep (8-9 hr in bed). The following day facial photographs were taken and, in a subset (n = 141), skin colour was measured using spectrophotometry. A separate set of participants (n = 63) later rated the photographs in terms of health, paleness and fatigue. The photographs were also digitally analysed with respect to eye openness, mouth curvature and periorbital darkness. The results showed that neither sleep deprivation nor the subjects' sleepiness was related to differences in any facial variable. Similarly, there was no difference in subjective ratings between the groups. Decreased skin yellowness, less eye openness, downward mouth curvature and periorbital darkness all predicted increased fatigue ratings by others. However, the combination of appearance variables could not be accurately used to classify sleep condition. These findings have implications for both face-to-face and computerised visual assessment of sleep loss and fatigue.

  • 17. Holding, J. B. C.
    et al.
    Laukka, Petri
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Kognitiv psykologi.
    Fischer, Håkan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Axelsson, John
    Sundelin, Tina
    Total sleep deprivation does not impact emotion categorisation in dynamic stimuli2016Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 25(S1), s. 152-152, artikkel-id P193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous studies have highlighted a deficit in facial emotion recognition after sleep loss. However, while some studies suggest an overall deficit in ability, others have only found effects in individual emotions, or no effect at all. The aim of this study was to investigate this relationship in a large sample and to utilise a dynamic test of emotion recognition in multiple modalities. 145 individuals (91 female, ages 18–45) participated in a sleep-deprivation experiment. Participants were randomised into: one night of total sleep deprivation (TSD) or normal sleep (8–9 h in bed). The following day participants completed a computerised emotional recognition test, consisting of 72 visual, audio, and audio-visual clips, representing 12 different emotions. The stimuli were divided into “easy” and “hard” depending on the intensity of emotional display. A mixed ANOVA revealed significant main effects of modality and difficulty, P < 0.001, but no main effect of condition, P = 0.31, on emotional recognition accuracy. Additionally, there was no interaction between condition and difficulty, P = 0.96, or modality, P = 0.67. This study indicates that sleep deprivation does not reduce the ability to recognise emotions. Given that some studies have only found effects on single emotions, it is possible that the effects of sleep loss are more specific than investigated here. However, it is also possible that previous findings relate to the types of static stimuli used. The ability to recognise emotions is key to social perception; this study suggests that this ability is resilient to one night of sleep deprivation.

  • 18.
    Ingre, Michael
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    van Leeuwen, Wessel M A
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Klemets, T
    Ullvetter, C
    Hough, S
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Karlsson, D
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Validating and extending the three process model (TPM) of alertness in airline operations.2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr S1, s. 264-264, artikkel-id P836Artikkel i tidsskrift (Annet vitenskapelig)
  • 19. Johansson, Peter J.
    et al.
    Crowley, Patrick
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Stockholm, Sweden.
    Franklin, Karl
    Garde, Anne Helene
    Hettiarachchi, Pasan
    Holtermann, Andreas
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Stockholm, Sweden.
    Lindberg, Eva
    Ljunggren, Mirjam
    Stamatakis, Emmanuel
    Theorell Haglöw, Jenny
    Svartengren, Magnus
    Development and performance of a sleep estimation algorithm using a single accelerometer placed on the thigh: an evaluation against polysomnography2023Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 32, nr 2, artikkel-id e13725Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accelerometers placed on the thigh provide accurate measures of daily physical activity types, postures and sedentary behaviours, over 24 h and across consecutive days. However, the ability to estimate sleep duration or quality from thigh-worn accelerometers is uncertain and has not been evaluated in comparison with the 'gold-standard' measurement of sleep polysomnography. This study aimed to develop an algorithm for sleep estimation using the raw data from a thigh-worn accelerometer and to evaluate it in comparison with polysomnography. The algorithm was developed and optimised on a dataset consisting of 23 single-night polysomnography recordings, collected in a laboratory, from 15 asymptomatic adults. This optimised algorithm was then applied to a separate evaluation dataset, in which, 71 adult males (mean [SD] age 57 [11] years, height 181 [6] cm, weight 82 [13] kg) wore ambulatory polysomnography equipment and a thigh-worn accelerometer, simultaneously, whilst sleeping at home. Compared with polysomnography, the algorithm had a sensitivity of 0.84 and a specificity of 0.55 when estimating sleep periods. Sleep intervals were underestimated by 21 min (130 min, Limits of Agreement Range [LoAR]). Total sleep time was underestimated by 32 min (233 min LoAR). Our results evaluate the performance of a new algorithm for estimating sleep and outline the limitations. Based on these results, we conclude that a single device can provide estimates of the sleep interval and total sleep time with sufficient accuracy for the measurement of daily physical activity, sedentary behaviour, and sleep, on a group level in free-living settings.

  • 20. Kaldo, Viktor
    et al.
    Bothelius, Kristoffer
    Blom, Kerstin
    Lindhe, Maria
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen. Stockholm County Council, Sweden.
    Larsson, Matilda
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen. Stockholm County Council, Sweden.
    Karimi, Kobra
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen.
    Melder, Susanne
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen.
    Bondestam, Viveka
    Ulfsparre, Charlotte
    Sternbrink, Klara
    Jernelöv, Susanna
    An open-ended primary-care group intervention for insomnia based on a self-help book: A randomized controlled trial and 4-year follow-up2020Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 29, nr 1, artikkel-id e12881Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chronic insomnia is a common and burdensome problem for patients seeking primary care. Cognitive behavioural therapy has been shown to be effective for insomnia, also when presented with co-morbidities, but access to sleep therapists is limited. Group-treatment and self-administered treatment via self-help books have both been shown to be efficacious treatment options, and the present study aimed to evaluate the effect of an open-ended group intervention based on a self-help book for insomnia, adapted to fit a primary-care setting. Forty primary-care patients with insomnia (mean age 55 years, 80% women) were randomized to the open-ended group intervention based on a cognitive behavioural therapy for insomnia self-help book or to a care as usual/wait-list control condition. Results show high attendance to group sessions and high treatment satisfaction. Participants in the control group later received the self-help book, but without the group intervention. The book-based group treatment resulted in significantly improved insomnia severity, as well as shorter sleep-onset latency, less wake time after sleep onset, and less use of sleep medication compared with treatment as usual. The improvements were sustained at a 4-year follow-up assessment. A secondary analysis found a significant advantage of the combination of the book and the open-ended group intervention compared with when the initial control group later used only the self-help book. An open-ended treatment group based on a self-help book for insomnia thus seems to be an effective and feasible intervention for chronic insomnia in primary-care settings.

  • 21.
    Kecklund, Göran
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Radun, Igor
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Ingre, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Fors, C.
    Ihlström, J.
    Anund, A.
    Bus drivers’ working hours and their effects on sleep and fatigue2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr S1, s. 286-287, artikkel-id P905Artikkel i tidsskrift (Annet vitenskapelig)
  • 22.
    Lowden, Arne
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Nagai, Roberta
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Åkerstedt, Torbjörn
    Karolinska Institutet, Sweden.
    Mild, Kjell Hansson
    Hillert, Lena
    Effects of evening exposure to electromagnetic fields emitted by 3G mobile phones on health and night sleep EEG architecture2019Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 28, nr 4, artikkel-id UNSP e12813Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies on sleep after exposure to radiofrequency electromagnetic fields have shown mixed results. We investigated the effects of double-blind radiofrequency exposure to 1,930-1,990 MHz, UMTS 3G signalling standard, time-averaged 10 g specific absorption rate of 1.6 W kg(-1) on self-evaluated sleepiness and objective electroencephalogram architecture during sleep. Eighteen subjects aged 18-19 years underwent 3.0 hr of controlled exposure on two consecutive days 19:45-23:00 hours (including 15-min break); active or sham prior to sleep, followed by full-night 7.5 hr polysomnographic recordings in a sleep laboratory. In a cross-over design, the procedure was repeated a week later with the second condition. The results for sleep electroencephalogram architecture showed no change after radiofrequency exposure in sleep stages compared with sham, but power spectrum analyses showed a reduction of activity within the slow spindle range (11.0-12.75 Hz). No differences were found for self-evaluated health symptoms, performance on the Stroop colour word test during exposure or for sleep quality. These results confirm previous findings that radiofrequency post-exposure in the evening has very little influence on electroencephalogram architecture but possible on spindle range activity.

  • 23.
    Lowden, Arne
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    van der Zande, BMI
    Geerdinc, L
    Change to higher illuminance and light colour temperature in open office, implications for sleep and sleepiness in Scandinavian winter2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr Suppl., s. 178-179, artikkel-id P586Artikkel i tidsskrift (Annet vitenskapelig)
  • 24.
    Magnusson Hanson, Linda L.
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Peristera, Paraskevi
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Chungkham, Holendro S.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Indian Statistical Institute, North-East Centre, India.
    Westerlund, Hugo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Psychosocial work characteristics, sleep disturbances and risk of subsequent depressive symptoms: a study of time-varying effect modification2017Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 26, nr 3, s. 266-276Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Job strain and low social support at work are recognized risk factors for depression. However, people with poor sleep may represent a high-risk group more likely to benefit from interventions against work stress. The present study examined whether the associations between these work stressors and depressive symptoms differed by strata of sleep disturbances (effect modification/effect moderation) considering repeat measures of work characteristics and sleep. The study was based on five biennial measurements of the Swedish Longitudinal Occupational Survey of Health, including 1537 respondents recurrently in paid work, from an originally representative sample of the Swedish working population. High work demands, low decision authority and low social support were measured waves 2 and 4, sleep disturbances (putative moderator/modifier) waves 1 and 3, and depressive symptoms (outcome) wave 5. Causal effect modification, whether the effect of working conditions differed by strata of sleep disturbances, was analysed by structural nested mean modelling estimated using a regression-with-residuals with inverse-probability-of-treatment weighting approach. High demands and low social support, but not low decision authority, influenced subsequent depressive symptoms. The relationship between social support and depressive symptoms was not apparently modified by sleep disturbances. However, disturbed sleep wave 3 modified the effect of high demands wave 4 (coefficient 1.77, P<0.05) on depressive symptoms wave 5. The results indicate that high job demands is a stronger risk factor for depressive symptoms in people with pre-existing sleep disturbances, suggesting that targeted workplace interventions may be more effective when it comes to preventing negative effects of job demands.

  • 25.
    Peristera, Paraskevi
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Nyberg, Anna
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Uppsala University, Sweden.
    Magnusson Hanson, Linda L.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Westerlund, Hugo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Platts, Loretta G.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    How consistently does sleep quality improve at retirement? Prospective analyses with group-based trajectory models2022Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 31, nr 2, artikkel-id e13474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Growing evidence indicates that retiring from paid work is associated, at least in the short-term, with dramatic reductions in sleep difficulties and more restorative sleep. However, much is still not known, in particular how universal these improvements are, how long they last, and whether they relate to the work environment. A methodological challenge concerns how to model time when studying abrupt changes such as retirement. Using data from Swedish Longitudinal Occupational Survey of Health (n = 2,148), we studied difficulties falling asleep, difficulties maintaining sleep, premature awakening, restless sleep, a composite scale of these items, and non-restorative sleep. We compared polynomial and B-spline functions to model time in group-based trajectory modelling. We estimated variations in the individual development of sleep difficulties around retirement, relating these to the pre-retirement work environment. Reductions in sleep difficulties at retirement were sudden for all outcomes and were sustained for up to 11 years for non-restorative sleep, premature awakening, and restless sleep. Average patterns masked distinct patterns of change: groups of retirees experiencing greatest pre-retirement sleep difficulties benefitted most from retiring. Higher job demands, lower work time control, lower job control, and working full-time were work factors that accounted membership in these groups. Compared to polynomials, B-spline models more appropriately estimated time around retirement, providing trajectories that were closer to the observed shapes. The study highlights the need to exercise care in modelling time over a sudden transition because using polynomials can generate artefactual uplifts or omit abrupt changes entirely, findings that would have fallacious implications.

  • 26.
    Petersen, Helena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    D'Onofrio, Paolo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Akerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Exercise is associated with changes in sleep architecture during stress2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr Suppl. 1Artikkel i tidsskrift (Annet vitenskapelig)
  • 27.
    Petersen, Helena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    D'Onofrio, Paolo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Thank god it's Friday - sleep improved2017Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 26, nr 5, s. 567-571Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The weekend is usually seen as a window of recovery. Thus, sleep before a day off may be less impaired than that before a workday. However, very few polysomnographical studies have investigated this hypothesis. Therefore, the aim of the present study was to compare sleep before a workday with that before a weekend. Seventeen teachers participated. Sleep was recorded with polysomnography on one weekday night during the workweek, and on a workday (Friday) followed by a day off. Sleep diaries and actigraphs were also used. Weekend sleep showed delayed bedtime and time of rising, a longer total sleep time (45 min), increased N3 and N1, and decreased N2 and REM. Sleep spindles were reduced. The results remained after truncation to the shortest common sleep duration (5 h). The increase in N3 from weekday sleep to Friday night sleep was positively correlated with N1 change (r = 0.853, P <= 0.001), and negatively correlated with N2 change (r = -0.614, P <= 0.001). Subjective ratings showed that weekend sleep was associated with less awakening problems and lower subjective arousal during the day. The authors concluded that weekend sleep was longer, and showed increased N3 and N1. The authors suggest that the N3 increase before the day off is a result of lower stress, while the N1 increase may be an effect of sleep spindle suppression via the increase of N3 (which would suppress sleep spindles), thus reducing N2 and enhancing N1.

  • 28.
    Petersen, Helena
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    D'Onofrio, Paolo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Nilsson, Jens
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Stress vulnerability and the effects of moderate daily stress on sleep polysomnography and subjective sleepiness2013Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 22, nr 1, s. 50-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The purpose of this study was to investigate if and how sleep physiology is affected by naturally occurring high work stress and identify individual differences in the response of sleep to stress. Probable upcoming stress levels were estimated through weekly web questionnaire ratings. Based on the modified FIRST-scale (Ford insomnia response to stress) participants were grouped into high (n = 9) or low (n = 19) sensitivity to stress related sleep disturbances (Drake et al., 2004). Sleep was recorded in 28 teachers with polysomnography, sleep diaries and actigraphs during one high stress and one low stress condition in the participants home. EEG showed a decrease in sleep efficiency during the high stress condition. Significant interactions between group and condition were seen for REM sleep, arousals and stage transitions. The sensitive group had an increase in arousals and stage transitions during the high stress condition and a decrease in REM, whereas the opposite was seen in the resilient group. Diary ratings during the high stress condition showed higher bedtime stress and lower ratings on the awakening index (insufficient sleep and difficulties awakening). Ratings also showed lower cognitive function and preoccupation with work thoughts in the evening. KSS ratings of sleepiness increased during stress for the sensitive group. Saliva samples of cortisol showed no effect of stress. It was concluded that moderate daily stress is associated with a moderate negative effect on sleep sleep efficiency and fragmentation. A slightly stronger effect was seen in the sensitive group.

  • 29.
    Radun, Igor
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. University of Helsinki, Finland.
    Levitski, Andres
    Wahde, Mattias
    Ingre, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden; Institute for Globally Distributed Open Research and Education (IGDORE), Sweden.
    Benderius, Ola
    Radun, Jenni
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Sleepy drivers on a slippery road: A pilot study using a driving simulator2022Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 31, nr 2, artikkel-id e13488Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sleepy drivers have problems with keeping the vehicle within the lines, and might often need to apply a sudden or hard corrective steering wheel movement. Such movements, if they occur while driving on a slippery road, might increase the risk of ending off road due to the unforgiving nature of slippery roads. We tested this hypothesis. Twelve young men participated in a driving simulator experiment with two counterbalanced conditions; dry versus slippery road x day (alert) versus night (sleepy) driving. The participants drove 52.5 km on a monotonous two-lane highway and rated their sleepiness seven times using the Karolinska Sleepiness Scale. Blink durations were extracted from an electrooculogram. The standard deviation of lateral position and the smoothness of steering events were measures of driving performance. Each outcome variable was analysed with mixed-effect models with road condition, time-of-day and time-on-task as predictors. The Karolinska Sleepiness Scale increased with time-on-task (p < 0.001) and was higher during night drives (p < 0.001), with a three-way interaction suggesting a small increased sleepiness with driving time at night with slippery road conditions (p = 0.012). Blink durations increased with time-on-task (p < 0.01) with an interaction between time-of-day and road condition (p = 0.040) such that physiological sleepiness was lower for sleep-deprived participants in demanding road conditions. The standard deviation of lateral position increased with time-on-task (p = 0.026); however, during night driving it was lower on a slippery road (p = 0.025). The results indicate that driving in demanding road condition (i.e. slippery road) might further exhaust already sleepy drivers, although this is not clearly reflected in driving performance.

  • 30. Rongen, E. F. E. R.
    et al.
    Rost-Ernst, A. E. W. G.
    Kloos, R.
    van Leeuwen, Wessel M. A.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Sleep and fatigue among officers on board gas tankers2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr Suppl. 1, s. 173-173Artikkel i tidsskrift (Annet vitenskapelig)
  • 31. Rosén, Ann
    et al.
    D'Onofrio, Paolo
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Kaldo, Viktor
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Stockholm, Sweden.
    Jernelöv, Susanna
    A comparison of sleep restriction and sleep compression on objective measures of sleep: A sub-sample from a large randomised controlled trial2023Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 32, nr 4, artikkel-id e13826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sleep restriction therapy is a central component of cognitive behavioural therapy for insomnia, but can lead to excessive sleepiness, which may impede treatment adherence. Sleep compression therapy has been suggested as a possibly gentler alternative. The aim of this study was to compare the effects of sleep restriction therapy and sleep compression therapy on objective measures of sleep, with a focus on magnitude and timing of effects. From a larger study of participants with insomnia, a sub-sample of 36 underwent polysomnographic recordings, before being randomised to either sleep restriction (n = 19) or sleep compression (n = 17) and receiving online treatment for 10 weeks. Assessments with polysomnography were also carried out after 2, 5, and 10 weeks of treatment. Data were analysed with multilevel linear mixed effect modelling. As per treatment instructions, participants in sleep restriction initially spent shorter time in bed compared with sleep compression. Participants in sleep restriction also showed an initial decrease of total sleep time, which was not seen in the sleep compression group. Both treatments led to improvements in sleep continuity variables, with a tendency for the improvements to come earlier during treatment in sleep restriction. No substantial differences were found between the two treatments 10 weeks after the treatment start. The results indicate that homeostatic sleep pressure may not be as important as a mechanism in sleep compression therapy as in sleep restriction therapy, and an investigation of other mechanisms is needed. In conclusion, the treatments led to similar changes in objective sleep at a somewhat different pace, and possibly through different mechanisms. 

  • 32. Salo, P
    et al.
    Ala-Mursula, L
    Rod, NH
    Tucker, Philip
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Pentti, J
    Kivimäki, M
    Vahtera, J
    Work time control and sleep disturbances2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr Suppl. 1, s. 138-138Artikkel i tidsskrift (Annet vitenskapelig)
  • 33.
    Schwarz, Johanna
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Gerhardsson, Andreas
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Arbets- och organisationspsykologi.
    Tamm, Sandra
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Fischer, Håkan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Mood impairment is stronger in young than in older adults after sleep deprivation2019Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 28, nr 4, artikkel-id e12801Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sleep deprivation commonly impairs affective regulation and causes worse mood. However, the majority of previous research concerns young adults. Because susceptibility to sleep deprivation and emotion regulation change distinctively across adult age, we tested here the hypothesis that the effect of sleep deprivation on mood is stronger in young than in older adults. In an experimental design, young (18–30 years) and older adults (60–72 years) participated in either a sleep control (young, n = 63; older, n = 47) or a total sleep deprivation condition (young, n = 61; older, n = 47). Sleepiness, mood and common symptoms of sleep deprivation were measured using established questionnaires and ratings. Sleep‐deprived participants felt more sleepy, stressed and cold, and reported lower vigour and positive affect, regardless of age. All the other outcome measures (negative affect, depression, confusion, tension, anger, fatigue, total mood disturbance, hunger, cognitive attenuation, irritability) showed a weaker response to sleep deprivation in the older group, as indicated by age*sleep deprivation interactions (ps < 0.05). The results show that older adults are emotionally less affected by sleep deprivation than young adults. This tolerance was mainly related to an attenuated increase in negative mood. This could possibly be related to the well‐known positivity effect, which suggests that older adults prioritize regulating their emotions to optimize well‐being. The results also highlight that caution is warranted when generalizing results from sleep deprivation studies across the adult lifespan.

  • 34.
    Schwarz, Johanna F. A.
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Ingre, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Fors, Carina
    Anund, Anna
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Taillard, Jacques
    Phillip, Pierre
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    In-car countermeasures open window and music revisited on the real road: popular but hardly effective against driver sleepiness2012Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 21, nr 5, s. 595-599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the effects of two very commonly used countermeasures against driver sleepiness, opening the window and listening to music, on subjective and physiological sleepiness measures during real road driving. In total, 24 individuals participated in the study. Sixteen participants received intermittent 10-min intervals of: (i) open window (2 cm opened); and (ii) listening to music, during both day and night driving on an open motorway. Both subjective sleepiness and physiological sleepiness (blink duration) was estimated to be significantly reduced when subjects listened to music, but the effect was only minor compared with the pronounced effects of night driving and driving duration. Open window had no attenuating effect on either sleepiness measure. No significant long-term effects beyond the actual countermeasure application intervals occurred, as shown by comparison to the control group (n = 8). Thus, despite their popularity, opening the window and listening to music cannot be recommended as sole countermeasures against driver sleepiness.

  • 35.
    Schwarz, Johanna F. A.
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Lindberg, Eva
    Gruber, Georg
    Fischer, Håkan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Theorell-Haglöw, Jenny
    Age affects sleep microstructure more than sleep macrostructure2017Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 26, nr 3, s. 277-287Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is well known that the quantity and quality of physiological sleep changes across age. However, so far the effect of age on sleep microstructure has been mostly addressed in small samples. The current study examines the effect of age on several measures of sleep macro- and microstructure in 211 women (22–71 years old) of the ‘Sleep and Health in Women’ study for whom ambulatory polysomnography was registered. Older age was associated with significantly lower fast spindle (effect size f2 = 0.32) and K-complex density (f2 = 0.19) during N2 sleep, as well as slow-wave activity (log) in N3 sleep (f2 = 0.21). Moreover, total sleep time (f2 = 0.10), N3 sleep (min) (f2 = 0.10), rapid eye movement sleep (min) (f2 = 0.11) and sigma (log) (f2 = 0.05) and slow-wave activity (log) during non-rapid eye movement sleep (f2 = 0.09) were reduced, and N1 sleep (f2 = 0.03) was increased in older age. No significant effects of age were observed on slow spindle density, rapid eye movement density and beta power (log) during non-rapid eye movement sleep. In conclusion, effect sizes indicate that traditional sleep stage scoring may underestimate age-related changes in sleep.

  • 36.
    Schwarz, Johanna
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Gerhardsson, Andreas
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Van Leeuwen, Wessel
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Fischer, Håkan
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi.
    Lekander, Mats
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    The effect of sleep loss on the response to acute psychosocial stress in young and elderly2016Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 25(S1), s. 48-48, artikkel-id 245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Both sleep loss and social stress are risk factors for health and performance ability. It is assumed that sleep and stress are bidirectional linked, but most of the previous research has focused on studying sleep problems as consequence of stress. We believe that it is important to improve our understanding of the reverse connection, which is less studied. This presentation will cover recent experimental human studies that have investigated how sleep loss affects stress responses and whether it makes individuals more vulnerable to psychosocial stress. A study by Minkel et al. (Health Psychology, 2014) reported that the cortisol response to an acute stress situation was increased after sleep deprivation compared with a control condition indicating a more pronounced activation of the hypothalamic-pituitary-adrenal stress axis. I will also present recently collected data from young (18–30 years) and older (60–72 years) subjects that participated in four conditions (between subject design):

    (i) normal night sleep.

    (ii) normal night sleep & acute stress (Trier Social Stress Test).

    (iii) total sleep deprivation.

    (iv) total sleep deprivation & acute stress.

    The presentation thus provides state of the art knowledge of the link between sleep loss and vulnerability to stress.

  • 37.
    Sundelin, Tina
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Stockholm, Sweden.
    Landry, Shane
    Axelsson, John
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Stockholm, Sweden.
    Is snoozing losing? Why intermittent morning alarms are used and how they affect sleep, cognition, cortisol, and mood2024Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 33, nr 3, artikkel-id e14054Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pressing the snooze button is a common way to start the day, but little is known about this behaviour. Through two studies we determined predictors and effects of snoozing. In Study 1 (n = 1732) respondents described their waking habits, confirming that snoozing is widespread, especially in younger individuals and later chronotypes. Morning drowsiness and shorter sleep were also more common for those who snooze. Study 2 was a within-subjects laboratory study (with polysomnography) on habitual snoozers (n = 31), showing that 30 min of snoozing improved or did not affect performance on cognitive tests directly upon rising compared to an abrupt awakening. Bayes factors indicate varying strengths of this evidence. Snoozing resulted in about 6 min of lost sleep, while preventing awakenings from slow-wave sleep (N3). There were no clear effects of snoozing on the cortisol awakening response, morning sleepiness, mood, or overnight sleep architecture. A brief snooze period may thus help alleviate sleep inertia, without substantially disturbing sleep, for late chronotypes and those with morning drowsiness.

  • 38. Tahmasian, Masoud
    et al.
    Aleman, André
    Andreassen, Ole A.
    Arab, Zahra
    Baillet, Marion
    Benedetti, Francesco
    Bresser, Tom
    Bright, Joanna
    Chee, Michael W. L.
    Chylinski, Daphne
    Cheng, Wei
    Deantoni, Michele
    Dresler, Martin
    Eickhoff, Simon B.
    Eickhoff, Claudia R.
    Elvsåshagen, Torbjørn
    Feng, Jianfeng
    Foster-Dingley, Jessica C.
    Ganjgahi, Habib
    Grabe, Hans J.
    Groenewold, Nynke A.
    Ho, Tiffany C.
    Hong, Seung Bong
    Houenou, Josselin
    Irungu, Benson
    Jahanshad, Neda
    Khazaie, Habibolah
    Kim, Hosung
    Koshmanova, Ekaterina
    Kocevska, Desi
    Kochunov, Peter
    Lakbila-Kamal, Oti
    Leerssen, Jeanne
    Li, Meng
    Luik, Annemarie
    Muto, Vincenzo
    Narbutas, Justinas
    Nilsonne, Gustav
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    O'Callaghan, Victoria S.
    Olsen, Alexander
    Osorio, Ricardo S.
    Poletti, Sara
    Poudel, Govinda
    Reesen, Joyce E.
    Reneman, Liesbeth
    Reyt, Mathilde
    Riemann, Dieter
    Rosenzweig, Ivana
    Rostampour, Masoumeh
    Saberi, Amin
    Schiel, Julian
    Schmidt, Christina
    Schrantee, Anouk
    Sciberras, Emma
    Silk, Tim J.
    Sim, Kang
    Smevik, Hanne
    Soares, Jair C.
    Spiegelhalder, Kai
    Stein, Dan J.
    Talwar, Puneet
    Tamm, Sandra
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden; University of Oxford, UK.
    Teresi, Giana L.
    Valk, Sofie L.
    Van Someren, Eus
    Vandewalle, Gilles
    Van Egroo, Maxime
    Völzke, Henry
    Walter, Martin
    Wassing, Rick
    Weber, Frederik D.
    Weihs, Antoine
    Westlye, Lars Tjelta
    Wright, Margaret J.
    Wu, Mon-Ju
    Zak, Nathalia
    Zarei, Mojtaba
    ENIGMA-Sleep: Challenges, opportunities, and the road map2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 6, artikkel-id e13347Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Neuroimaging and genetics studies have advanced our understanding of the neurobiology of sleep and its disorders. However, individual studies usually have limitations to identifying consistent and reproducible effects, including modest sample sizes, heterogeneous clinical characteristics and varied methodologies. These issues call for a large-scale multi-centre effort in sleep research, in order to increase the number of samples, and harmonize the methods of data collection, preprocessing and analysis using pre-registered well-established protocols. The Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) consortium provides a powerful collaborative framework for combining datasets across individual sites. Recently, we have launched the ENIGMA-Sleep working group with the collaboration of several institutes from 15 countries to perform large-scale worldwide neuroimaging and genetics studies for better understanding the neurobiology of impaired sleep quality in population-based healthy individuals, the neural consequences of sleep deprivation, pathophysiology of sleep disorders, as well as neural correlates of sleep disturbances across various neuropsychiatric disorders. In this introductory review, we describe the details of our currently available datasets and our ongoing projects in the ENIGMA-Sleep group, and discuss both the potential challenges and opportunities of a collaborative initiative in sleep medicine.

  • 39.
    Tucker, Philip
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Swansea University, UK.
    Harmä, Mikko
    Ojajärvi, Anneli
    Kivimäki, Mika
    Leineweber, Constanze
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet.
    Oksanen, Tuula
    Salo, Paula
    Vahtera, Jussi
    Association of rotating shift work schedules and the use of prescribed sleep medication: A prospective cohort study2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 6, artikkel-id e13349Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We examined whether working rotating shifts, with or without night work, is associated with the purchase of prescribed sleep medication, and whether the association is dependent on age. Data were obtained from a longitudinal cohort study of Finnish public sector employees who responded to questions on work schedule and background characteristics in 2000, 2004 and 2008. The data were linked to national register data on redeemed prescriptions of hypnotic and sedative medications, with up to 11 years of follow-up. Age stratified Cox proportional hazard regression models were computed to examine incident use of medication comparing two groups of rotating shift workers (those working shifts that included night shifts and those whose schedules did not include night shifts) with day workers who worked in a similar range of occupations. Shift work with night shifts was associated with increased use of sleep medication in all age groups, after adjustments for sex, occupational status, marital status, alcohol consumption, smoking and physical activity levels (hazard ratio [HR], [95% confidence interval, CI] 1.14 [1.01-1.28] for age group <= 39 years; 1.33 [1.19-1.48] for age group 40-49 years; 1.28 [1.13-1.44] for age group >= 50 years). Shift work without nights was associated with medication use in the two older age groups (HR [95% CI] 1.14 [1.01-1.29] and 1.17 [1.05-1.31] for age groups 40-49 years and >50 years, respectively). These findings suggest that circadian disruption and older age puts rotating shift workers, and especially those who work nights, at increased risk of developing clinically significant levels of sleep problems.

  • 40.
    Watling, Christopher N.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Queensland University of Technology (QUT), Australia.
    Young drivers who continue to drive while sleepy: What are the associated sleep- and driving-related factors?2020Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 29, nr 3, artikkel-id e12900Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Crashes due to sleepiness account for a substantial proportion of road crash incidents. The purpose of the current study was to examine several sleep-related factors and driving-related factors for their association with self-reports of continuing to drive while sleepy. In total 257 young drivers aged 18-25 years completed an online survey that assessed factors such as sleep quality, sleep duration and consistency, excessive daytime sleepiness, experiences with sleepiness and their driving-related behaviours. The results demonstrate that being older, having a perceived ability to overcome sleepiness, committing more highway code violations and having experienced a sleep-related close call were positively associated with an increased likelihood of continuing to drive while sleepy. The obtained results highlight the acceptance of risky driving behaviours among some younger drivers. Younger drivers' risky driving behaviour is certainly a road safety concern given the impairment associated with sleepiness and their over-representation in road crash incidents.

  • 41.
    Watling, Christopher N.
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Queensland University of Technology, Australia.
    Åkerstedt, Torbjörn
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Radboud University, Netherlands.
    Anund, Anna
    Do repeated rumble strip hits improve driver alertness?2016Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 25, nr 2, s. 241-247Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Driving while sleepy is associated with increased crash risk. Rumble strips are designed to alert a sleepy or inattentive driver when they deviate outside their driving lane. The current study sought to examine the effects of repeated rumble strip hits on levels of physiological and subjective sleepiness as well as simulated driving performance. In total, 36 regular shift workers drove a high-fidelity moving base simulator on a simulated road with rumble strips installed at the shoulder and centre line after a working a full night shift. The results show that, on average, the first rumble strip occurred after 20 min of driving, with subsequent hits occurring 10 min later, with the last three occurring approximately every 5 min thereafter. Specifically, it was found that the first rumble strip hit reduced physiological sleepiness; however, subsequent hits did not increase alertness. Moreover, the results also demonstrate that increased subjective sleepiness levels, via the Karolinska Sleepiness Scale, were associated with a greater probability of hitting a rumble strip. The present results suggest that sleepiness is very resilient to even strongly arousing stimuli, with physiological and subjective sleepiness increasing over the duration of the drive, despite the interference caused by rumble strips.

  • 42.
    Åkerstedt, Torbjorn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Schwarz, Johanna
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Gruber, Georg
    Theorell-Haglöw, Jenny
    Lindberg, Eva
    Short sleep-poor sleep? A polysomnographic study in a large population-based sample of women2019Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 28, nr 4, artikkel-id e12812Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a lack of studies on the association between total sleep time (TST) and other polysomnographical parameters. A key question is whether a short sleep is an expression of habitual short sleep, or whether it reflects temporary impairment. The purpose of the present study was to investigate the association between TST and amount of sleep stages and sleep continuity measures, in a large population-based sample of women (n = 385), sleeping at home in a normal daily life setting. The results show that sleep efficiency, N1 (min), N2 (min), REM (min), REM% and proportion of long sleep segments, increased with increasing TST, whereas the number of awakenings/hr, the number of arousals/hr, N1% and REM intensity decreased. In addition, longer sleep was more associated with TST being perceived as of usual duration and with better subjective sleep quality. TST was not associated with habitual reported sleep duration. It was concluded that short TST of a recorded sleep in a real-life context may be an indicator of poor objective sleep quality for that particular sleep episode. Because individuals clearly perceived this reduction, it appears that self-reports of poor sleep quality often may be seen as indicators of poor sleep quality. It is also concluded that PSG-recorded sleep duration does not reflect habitual reported sleep duration in the present real-life context.

  • 43.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet.
    Anund, Anna
    Axelsson, John
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Subjective sleepiness is a sensitive indicator of insufficient sleep and impaired waking function2014Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 23, nr 3, s. 240-252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main consequence of insufficient sleep is sleepiness. While measures of sleep latency, continuous encephalographical/electro-oculographical (EEG/EOG) recording and performance tests are useful indicators of sleepiness in the laboratory and clinic, they are not easily implemented in large, real-life field studies. Subjective ratings of sleepiness, which are easily applied and unobtrusive, are an alternative, but whether they measure sleepiness sensitively, reliably and validly remains uncertain. This review brings together research relevant to these issues. It is focused on the Karolinska Sleepiness Scale (KSS), which is a nine-point Likert-type scale. The diurnal pattern of sleepiness is U-shaped, with high KSS values in the morning and late evening, and with great stability across years. KSS values increase sensitively during acute total and repeated partial sleep deprivation and night work, including night driving. The effect sizes range between 1.5 and 3. The relation to driving performance or EEG/EOG indicators of sleepiness is highly significant, strongly curvilinear and consistent across individuals. High (>6) KSS values are associated particularly with impaired driving performance and sleep intrusions in the EEG. KSS values are also increased in many clinical conditions such as sleep apnea, depression and burnout. The context has a strong influence on KSS ratings. Thus, physical activity, social interaction and light exposure will reduce KSS values by 1-2 units. In contrast, time-on-task in a monotonous context will increase KSS values by 1-2 units. In summary, subjective ratings of sleepiness as described here is as sensitive and valid an indicator of sleepiness as objective measures, and particularly suitable for field studies.

  • 44.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Axelsson, John
    Lekander, Mats
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Orsini, Nicola
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    The daily variation in sleepiness and its relation to the preceding sleep episode - a prospective study across 42days of normal living2013Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 22, nr 3, s. 258-265Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sleepiness is linked to accidents and reduced performance, and is usually attributed to short/poor prior sleep and sleepiness. However, while the link between reduced sleep and subsequent sleepiness is well established in laboratory experiments of sleep reduction, very little is known about the day-to-day variation of sleepiness in everyday life and its relation to the immediately preceding sleep episode. The purpose of the present study was to investigate the characteristics of this relation across 42 consecutive days. Fifty volunteers participated. Self-reports of sleep were given in the morning and recorded with actigraphy; health was rated in the evening; and sleepiness was rated at eight points during the day (on a scale of 1-9). Results from mixed-model regression analyses showed that, on average, total sleep time predicted sleepiness during the rest of the day across the 42 days, with sleepiness increasing with shorter preceding sleep (β = -0.15 units h(-1) , P < 0.001). Sleepiness also increased with earlier time of rising and lower-rated sleep quality. Days off reduced sleepiness, but was accounted for by sleep. Self-rated health improved when sleepiness was low during the same day (β = -0.36 unit unit(-1) of rated health, P < 0.001), but the two were measured simultaneously. Napping was related to high sleepiness during the same day. Actigraphy measures of sleep duration showed similar, but somewhat weaker, effects than diary measures. It was concluded that the main determinants of daytime sleepiness in a real-life day-to-day context were short sleep, poor sleep and early rising, and that days with high sleepiness ended with ratings of poorer health.

  • 45.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Biologisk psykologi. Karolinska Institutet, Sweden.
    Bellocco, Rino
    Widman, Linnea
    Eriksson, Julia
    Ye, Weimin
    Adami, Hans-Olov
    Trolle Lagerros, Ylva
    The association of short and long sleep with mortality in men and women2024Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 33, nr 2, artikkel-id e13931Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Both short (< 6 hr) and long (> 8 hr) sleep are associated with increased mortality. We here investigated whether the association between sleep duration and all-cause, cardiovascular disease and cancer mortality differs between men and women. A cohort of 34,311 participants (mean age and standard deviation = 50.5 ± 15.5 years, 65% women), with detailed assessment of sleep at baseline and up to 20.5 years of follow-up (18 years for cause-specific mortality), was analysed using Cox proportional hazards model to estimate HRs with 95% confidence intervals. After adjustment for covariates, all-cause, cardiovascular disease and cancer mortalities were increased for both < 5 hr and ≥ 9 hr sleep durations (with 6 hr as reference). For all-cause mortality, women who slept < 5 hr had a hazard ratio = 1.54 (95% confidence interval = 1.32–1.80), while the corresponding hazard ratio was 1.05 (95% confidence interval = 0.88–1.27) for men, the interaction being significant (p < 0.05). For cardiovascular disease mortality, exclusion of the first 2 years of exposure, as well as competing risk analysis eliminated the originally significant interaction. Cancer mortality did not show any significant interaction. Survival analysis of the difference between the reference duration (6 hr) and the short duration (< 5 hr) during follow-up showed a gradually steeper reduction of survival time for women than for men for all-cause mortality. We also observed that the lowest cancer mortality appeared for the 5-hr sleep duration. In conclusion, the pattern of association between short sleep duration and all-cause mortality differed between women and men, and the difference between men and women increased with follow-up time.

  • 46.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Ghilotti, Francesca
    Grotta, Alessandra
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Centrum för forskning om ojämlikhet i hälsa (CHESS). Karolinska Institutet, Sweden.
    Zhao, Hongwei
    Adami, Hans-Olov
    Trolle-Lagerros, Ylva
    Bellocco, Rino
    Sleep duration and mortality - Does weekend sleep matter?2019Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 28, nr 1, artikkel-id e12712Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous studies have found a U-shaped relationship between mortality and (weekday) sleep duration. We here address the association of both weekday and weekend sleep duration with overall mortality. A cohort of 43,880 subjects was followed for 13 years through record-linkages. Cox proportional hazards regression models with attained age as time-scale were fitted to estimate multivariable-adjusted hazard ratios and 95% confidence intervals for mortality; stratified analyses on age (<65 years, >= 65 years) were conducted. Among individuals <65 years old, short sleep (<= 5 hr) during weekends at baseline was associated with a 52% higher mortality rate (hazard ratios 1.52; 95% confidence intervals 1.15-2.02) compared with the reference group (7 hr), while no association was observed for long (>= 9 hr) weekend sleep. When, instead, different combinations of weekday and weekend sleep durations were analysed, we observed a detrimental association with consistently sleeping <= 5 hr (hazard ratios 1.65; 95% confidence intervals 1.22-2.23) or >= 8 hr (hazard ratios 1.25; 95% confidence intervals 1.05-1.50), compared with consistently sleeping 6-7 hr per day (reference). The mortality rate among participants with short sleep during weekdays, but long sleep during weekends, did not differ from the rate of the reference group. Among individuals >= 65 years old, no association between weekend sleep or weekday/weekend sleep durations and mortality was observed. In conclusion, short, but not long, weekend sleep was associated with an increased mortality in subjects <65 years. In the same age group, short sleep (or long sleep) on both weekdays and weekend showed increased mortality. Possibly, long weekend sleep may compensate for short weekday sleep.

  • 47.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Hallvig, David
    Anund, Anna
    Fors, Carina
    Schwarz, Johanna
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Having to stop driving at night because of dangerous sleepiness - awareness, physiology and behaviour2013Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 22, nr 4, s. 380-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A large number of accidents are due to the driver falling asleep at the wheel, but details of this link have not been studied on a real road. The purpose of the present study was to describe the development of sleepiness indicators, leading to the drive being terminated prematurely by the onboard expert driving instructor because of imminent danger. Eighteen individuals participated during a day drive and a night drive on a motorway (both 90 min). Eight drivers terminated (N) prematurely (after 43 min) because of sleep-related imminent danger [according to the driving instructor or their own judgement (two cases)]. The results showed very high sleepiness ratings (8.5 units on the Karolinska Sleepiness Scale) immediately before termination (<7 at a similar time interval for those 10 who completed the drive). Group N also showed significantly higher levels of sleep intrusions on the electroencephalography/electro-oculography (EEG/EOG) than those who completed the drive (group C). The sleep intrusions were increased in group N during the first 40 min of the night drive. During the day drive, sleep intrusions were increased significantly in group N. The night drive showed significant increases of all sleepiness indicators compared to the day drive, but also reduced speed and driving to the left in the lane. It was concluded that 44% of drivers during late-night driving became dangerously sleepy, and that this group showed higher perceived sleepiness and more sleep intrusions in the EEG/EOG.

  • 48.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Hallvig, David
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet. Karolinska Institute, Sweden.
    Normative data on the diurnal pattern of the Karolinska Sleepiness Scale ratings and its relation to age, sex, work, stress, sleep quality and sickness absence/illness in a large sample of daytime workers2017Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 26, nr 5, s. 559-566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Self-rated sleepiness responds to sleep loss, time of day and work schedules. There is, however, a lack of a normative reference showing the diurnal pattern during a normal working day, compared with a day off, as well as differences depending on stress, sleep quality, sex, age and being sick listed. The present study sought to provide such data for the Karolinska Sleepiness Scale. Participants were 431 individuals working in medium-sized public service units. Sleepiness (Karolinska Sleepiness Scale, scale 1-9) was rated at six times a day for a working week and 2 days off (>90.000 ratings). The results show a clear circadian pattern, with high values during the morning (4.5 at 07:00 hours) and evening (6.0 at 22:00 hours), and with low values (3-4) during the 10:0016: 00 hours span. Women had significantly higher (0.5 units) Karolinska Sleepiness Scale values than men, as did younger individuals (0.3 units), those with stress (1.3 units above the low-stress group) and those with poor sleep quality (1.0 units above those with qood sleep quality). Days off showed reduced sleepiness (0.7 units), while being sick listed was associated with an increased sleepiness (0.8 units). Multiple regression analysis of mean sleepiness during the working week yielded mean daytime stress, mean sleep quality, age, and sex as predictors (not sleep duration). Improved sleep quality accounted for the reduced sleepiness during days off, but reduced stress was a second factor. Similar results were obtained in a longitudinal mixed-model regression analysis across the 7 days of the week. The percentage of ratings at Karolinska Sleepiness Scale risk levels (8 + 9) was 6.6%, but most of these were obtained at 22:00 hours. It was concluded that sleepiness ratings are strongly associated with time of day, sleep quality, stress, work day/day off, being ill, age, and sex.

  • 49.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Ingre, Michael
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Kecklund, Göran
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Stressforskningsinstitutet.
    Anund, Anna
    Sandberg, David
    Wahde, Mattias
    Philip, Pierre
    Kronberg, Peter
    Reaction of sleepiness indicators to partial sleep deprivation, time of day and time on task in a driving simulator - the DROWSI project2010Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 19, nr 2, s. 298-309Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies of driving and sleepiness indicators have mainly focused on prior sleep reduction. The present study sought to identify sleepiness indicators responsive to several potential regulators of sleepiness: sleep loss, time of day (TOD) and time on task (TOT) during simulator driving. Thirteen subjects drove a high-fidelity moving base simulator in six 1-h sessions across a 24-h period, after normal sleep duration (8 h) and after partial sleep deprivation (PSD; 4 h). The results showed clear main effects of TOD (night) and TOT but not for PSD, although the latter strongly interacted with TOD. The most sensitive variable was subjective sleepiness, the standard deviation of lateral position (SDLAT) and measures of eye closure [duration, speed (slow), amplitude (low)]. Measures of electroencephalography and line crossings (LCs) showed only modest responses. For most variables individual differences vastly exceeded those of the fixed effects, except for subjective sleepiness and SDLAT. In a multiple regression analysis, SDLAT, amplitude/peak eye-lid closing velocity and blink duration predicted subjective sleepiness bouts with a sensitivity and specificity of about 70%, but were mutually redundant. The prediction of LCs gave considerably weaker, but similar results. In summary, SDLAT and eye closure variables could be candidates for use in sleepiness-monitoring devices. However, individual differences are considerable and there is need for research on how to identify and predict individual differences in susceptibility to sleepiness.

  • 50.
    Åkerstedt, Torbjörn
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Psykologiska institutionen, Stressforskningsinstitutet. Karolinska Institutet, Sweden.
    Klemets, Tomas
    Karlsson, David
    Häbel, Henrike
    Widman, Linnea
    Sallinen, Mikael
    Acute and cumulative effects of scheduling on aircrew fatigue in ultra-short-haul operations2021Inngår i: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 30, nr 5, artikkel-id e13305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aircrew fatigue constitutes a safety hazard in aviation, which authorities attempt to mitigate through flight time limitations. Some gaps in knowledge exist, however. The purpose of the present study was to investigate the associations of schedule characteristics with fatigue and amount of sleep in the acute 24-h window, and as cumulative effects across the 7-day work period. One hundred and six aircrew (14% cabin crew) participated. They rated fatigue on the Karolinska Sleepiness Scale (KSS) three times per flight day for four 7-day work periods, with up to 7 days off between work periods. Mixed model regression was applied to the data. In the multivariable model, more sleep was associated with lower fatigue (p = .000)), corresponding to 0.26 KSS units less per hour of sleep. Very early, early and late duty types, as well as duty time, were associated with higher fatigue. For the 7-day work period, accumulation of very early duties and longer duty time were associated with increased fatigue, and more accumulated sleep was associated with lower fatigue in the adjusted model (0.08 KSS units per hour of sleep) (p = .000). Accumulated duty time was not significant when analysed as a single variable, but became so after adjustment for sleep. The results suggest that sleep, duty time and early starts are important predictors of fatigue in the 24-h window and that the number of very early starts and short sleep have cumulative effects on fatigue across a 7-day work period.

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