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  • 1.
    Dahlgren, Anna
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Karolinska Institute, Sweden.
    Tucker, Philip
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Swansea University, UK.
    Gustavsson, Petter
    Rudman, Ann
    Quick returns and night work as predictors of sleep quality, fatigue, work-family balance and satisfaction with work hours2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 6, p. 759-767Article in journal (Refereed)
    Abstract [en]

    Quick returns (intervals of <11 h between the end of one shift and the start of the next) are associated with short sleeps and fatigue on the subsequent shift. Recent evidence suggests that shift workers regard quick returns as being more problematic than night work. The current study explored quick returns and night work in terms of their impact on sleep, unwinding, recovery, exhaustion, satisfaction with work hours and work-family interference. Data from the 2006 cohort of Swedish nursing students within the national Longitudinal Analysis of Nursing Education (LANE) study were analysed (N = 1459). Respondents completed a questionnaire prior to graduation (response rate 69.2%) and 3 years after graduation (65.9%). The analyses examined associations between frequency of quick returns and night work and measures taken in year three, while adjusting for confounding factors (in year three and prior graduation). Frequency of quick returns was a significant predictor of poor sleep quality, short sleeps, unwinding, exhaustion, satisfaction with work hours and work-to-family interference, with higher frequency predicting more negative outcomes. Quick returns did not predict recovery after rest days. Frequency of night work did not predict any of the outcomes. In conclusion, quick returns were an important determinant of sleep, recovery and wellbeing, whereas night work did not show such an association.

  • 2. Dahlgren, Anna
    et al.
    Åkerstedt, Torbjörn
    Kecklund, Göran
    Individual differences in the diurnal cortisol response to stress2004In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 21, no 6, p. 913-922Article in journal (Refereed)
    Abstract [en]

    The objectives of this study were to explore individual differences associated with diverse reactions in cortisol secretion under different stress levels. This study was part of a larger project concerning working hours and health. Thirty-four whitecollar workers participated under two different conditions; one work week with a high stress level (H) and one with a lower stress level (L) as measured through self-rated stress during workdays. Based on the morning cortisol concentration during a workday subjects were divided into two groups. One group consisted of subjects whose morning level of cortisol increased in response to the high-stress week, compared to their morning levels in the low-stress condition (Group 1). The other group consisted of subjects whose morning cortisol response was the opposite, with a lower level under the high stress condition (Group 2). Subjects wore actiwatches, completed a sleep diary, and rated their sleepiness and stress for one work week in each condition, i.e., high and low stress. Saliva samples for measures of cortisol were collected on a Wednesday. Group 2 reported higher workload, fatigue, and exhaustion during both weeks. Since there were no differences in perceived stress, neither within nor between groups, the data indicate that there are other factors influencing morning cortisol. The results suggest that one component modulating the cortisol response might be the level of exhaustion, probably related to work overload. Higher levels of stress in exhausted individuals might suppress morning cortisol levels.

  • 3.
    Dahlgren, Anna
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Psychology. National Institute for Psychosocial Medicine.
    Åkerstedt, Torbjörn
    National Institute for Psychosocial Medicine.
    Kecklund, Göran
    National Institute for Psychosocial Medicine.
    Individual differences in the diurnal cortisol response to stress2004In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 21, no 6, p. 913-922Article in journal (Refereed)
    Abstract [en]

    The objectives of this study were to explore individual differences associated with diverse reactions in cortisol secretion under different stress levels. This study was part of a larger project concerning working hours and health. Thirty-four whitecollar workers participated under two different conditions; one work week with a high stress level (H) and one with a lower stress level (L) as measured through self-rated stress during workdays. Based on the morning cortisol concentration during a workday subjects were divided into two groups. One group consisted of subjects whose morning level of cortisol increased in response to the high-stress week, compared to their morning levels in the low-stress condition (Group 1). The other group consisted of subjects whose morning cortisol response was the opposite, with a lower level under the high stress condition (Group 2). Subjects wore actiwatches, completed a sleep diary, and rated their sleepiness and stress for one work week in each condition, i.e., high and low stress. Saliva samples for measures of cortisol were collected on a Wednesday. Group 2 reported higher workload, fatigue, and exhaustion during both weeks. Since there were no differences in perceived stress, neither within nor between groups, the data indicate that there are other factors influencing morning cortisol. The results suggest that one component modulating the cortisol response might be the level of exhaustion, probably related to work overload. Higher levels of stress in exhausted individuals might suppress morning cortisol levels.

  • 4.
    Danielsson, Katarina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Psychiatry, University Hospital.
    Markström, Agneta
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Respiratory Medicine and Allergology.
    Broman, Jan-Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Respiratory Medicine and Allergology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Psychiatry, University Hospital.
    von Knorring, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Psychiatry, University Hospital.
    Jansson-Fröjmark, Markus
    Institutionen för Psykologi, Stockholms Universitet.
    Delayed sleep phase disorder in a Swedish cohort of adolescents and young adults: Prevalence and associated factors2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 10, p. 1331-1339Article in journal (Refereed)
    Abstract [en]

    A delayed sleep-wake and circadian rhythm often occurs during puberty. While some individuals only develop a delayed sleep phase (DSP), others will fulfill the criteria for the diagnosis of delayed sleep phase disorder (DSPD). All previous studies have however not separated DSP from DSPD, and, as a result, the prevalence and associated factors are largely unknown for the two conditions individually. We estimated the prevalence of DSP and DSPD in a Swedish cohort of adolescents and young adults. We also investigated associated factors in the two conditions relative to each other and individuals with no delayed sleep phase. A questionnaire regarding sleep patterns, demographics, substance use/abuse, and symptoms of depression, anxiety, worry, and rumination was sent to 1000 randomly selected participants (16–26 years of age) in Uppsala, Sweden (response rate = 68%). DSP was defined as a late sleep onset and a preferred late wake up time. The DSPD diagnosis was further operationalized according to the Diagnostic and Statistical Manual of Mental Disorders, Edition 5 (DSM-5) criteria including insomnia or excessive sleepiness, distress or dysfunction caused by the delayed sleep phase and that the sleep problem had been evident for 3 months. DSP occurred at a frequency of 4.6% and DSPD at a frequency of 4% in the investigated cohort. DSP was more common in males and was associated with not attending educational activity or work, having shift work, nicotine and alcohol use and less rumination. DSPD was equally common in males and females and was associated with not attending educational activity or work and with elevated levels of anxiety. Both DSP and DSPD appear to be common in adolescents and young adults in this Swedish cohort. No educational activity or work was associated with both DSP and DSPD. However, there were also apparent differences between the two groups in shift work, substance use and mental health, relative to persons with no delayed sleep phase. Thus, it seems reasonable to assess DSP and DSPD as distinct entities in future studies.

  • 5. Danielsson, Katarina
    et al.
    Markström, Agneta
    Broman, Jan-Erik
    von Knorring, Lars
    Jansson-Fröjmark, Markus
    Stockholm University, Faculty of Social Sciences, Department of Psychology, Clinical psychology.
    Delayed sleep phase disorder in a Swedish cohort of adolescents and young adults: Prevalence and associated factors2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 10, p. 1331-1339Article in journal (Refereed)
    Abstract [en]

    A delayed sleep-wake and circadian rhythm often occurs during puberty. While some individuals only develop a delayed sleep phase (DSP), others will fulfill the criteria for the diagnosis of delayed sleep phase disorder (DSPD). All previous studies have however not separated DSP from DSPD, and, as a result, the prevalence and associated factors are largely unknown for the two conditions individually. We estimated the prevalence of DSP and DSPD in a Swedish cohort of adolescents and young adults. We also investigated associated factors in the two conditions relative to each other and individuals with no DSP. A questionnaire regarding sleep patterns, demographics, substance use/abuse and symptoms of depression, anxiety, worry and rumination was sent to 1000 randomly selected participants (16-26 years of age) in Uppsala, Sweden (response rate = 68%). DSP was defined as a late sleep onset and a preferred late wake-up time. The DSPD diagnosis was further operationalized according to the Diagnostic and Statistical Manual of Mental Disorders, Edition 5 (DSM-5) criteria including insomnia or excessive sleepiness, distress or dysfunction caused by the DSP and that the sleep problem had been evident for 3 months. DSP occurred at a frequency of 4.6% and DSPD at a frequency of 4% in the investigated cohort. DSP was more common in males and was associated with not attending educational activity or work, having shift work, nicotine and alcohol use and less rumination. DSPD was equally common in males and females and was associated with not attending educational activity or work and with elevated levels of anxiety. Both DSP and DSPD appear to be common in adolescents and young adults in this Swedish cohort. No educational activity or work was associated with both DSP and DSPD. However, there were also apparent differences between the two groups in shift work, substance use and mental health, relative to persons with no DSP. Thus, it seems reasonable to assess DSP and DSPD as distinct entities in future studies.

  • 6.
    Danielsson, Katarina
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Psychiatry, University Hospital.
    Sakarya, Aysegül
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Psychiatry, University Hospital.
    Jansson-Fröjmark, Markus
    Department of Clinical Neuroscience, Karolinska Institute.
    The reduced Morningness–Eveningness Questionnaire: Psychometric properties and related factors in a young Swedish population2019In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 36, no 4, p. 530-540Article in journal (Refereed)
    Abstract [en]

    During puberty, there is a delay in sleep patterns and the circadian clock, and the prevalence of sleep difficulties is high among young adults. Thus, it is important to be able to measure chronotype (CT) in this group, both in the clinic and for broader epidemiological studies, to better understand the sleep difficulties observed. The reduced version of one of the most widely used questionnaire to measure CT, the Horne & Östberg Morningness–Eveningness Questionnaire (MEQ), has been developed and validated in many languages. The aim of the present study was to investigate the reliability and validity of the Swedish reduced MEQ (rMEQ) and to investigate factors correlated with rMEQ scores in a random sample of young Swedish participants. We sent the rMEQ, sleep questions, demographic questions, the Insomnia Severity Index (ISI), the Epworth Sleepiness Scale, and the Hospital Anxiety and Depression Scale (HADS-A and HADS-D) to 1000 randomly selected individuals aged 16–26 years in Uppsala, Sweden (response rate = 68%). A parallel analysis of the rMEQ revealed a single factor solution. Inter-item correlations within the questionnaire were between 0.08 and 0.46. One of the rMEQ items displayed weak correlations with the other questions. Cronbach’s alpha of the rMEQ was 0.68. Low rMEQ scores (eveningness) were correlated with more frequent late bedtimes and difficulties getting up in the morning. Lower rMEQ scores were significantly related to male sex, no educational activity or work, nicotine use, younger age, and higher ISI and HADS-D scores. Even though the inter-item correlations of the rMEQ were very low to moderate, the rMEQ had a Cronbach’s alpha not far off from acceptable levels, and the strong correlations of the rMEQ scores with responses to the sleep questions indicated that the rMEQ had an adequate validity. To conclude, the rMEQ can be used to effectively estimate CT when a short questionnaire is required; however, caution should be taken when interpreting the results considering the reliability of the questionnaire.

  • 7. Eckerberg, Berndt
    et al.
    Lowden, Arne
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Nagai, Roberta
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Melatonin treatment effects on adolescent students' sleep timing and sleepiness in a placebo-controlled crossover study2012In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 29, no 9, p. 1239-1248Article in journal (Refereed)
    Abstract [en]

    During the last few decades, the incidence of sleep-onset insomnia, due to delay of circadian phase, has increased substantially among adolescents all over the world. We wanted to investigate whether a small dose of melatonin given daily, administered in the afternoon, could advance the sleep timing in teenagers. Twenty-one students, aged 14-19 yrs, with sleep-onset difficulties during school weeks were recruited. The study was a randomized, double blind, placebo (PL)-controlled crossover trial, lasting 5 wks. During the first 6 d in wks 2 and 4, the students received either PL or melatonin (1 mg) capsules between 16:30 and 18:00 h. During the first 6 d of wk 5, all students received melatonin. Wks 1 and 3 were capsule-free. In the last evening of each week and the following morning, the students produced saliva samples at home for later melatonin analysis. The samples were produced the same time each week, as late as possible in the evening and as early as possible in the morning. Both the student and one parent received automatic mobile text messages 15 min before saliva sampling times and capsule intake at agreed times. Diaries with registration of presumed sleep, subjective sleepiness during the day (Karolinska Sleepiness Scale, KSS) and times for capsule intake and saliva samplings were completed each day. Primary analysis over 5 wks gave significant results for melatonin, sleep and KSS. Post hoc analysis showed that reported sleep-onset times were advanced after melatonin school weeks compared with PL school weeks (p  <  .005) and that sleep length was longer (p  <  .05). After the last melatonin school week, the students fell asleep 68 min earlier and slept 62 min longer each night compared with the baseline week. Morning melatonin values in saliva diminished compared with PL (p  <  .001) and evening values increased (p  <  .001), indicating a possible sleep phase advance. Compared with PL school weeks, the students reported less wake up (p  <  .05), less school daytime sleepiness (p  <  .05) and increased evening sleepiness (p  <  .005) during melatonin weeks. We conclude that a small dose of melatonin given daily, administered in the afternoon, could advance the sleep timing and make the students more alert during school days even if they continued their often irregular sleep habits during weekends.

  • 8.
    Eriksen, Claire A.
    et al.
    Institute for Psychosocial Factors and Health (IPM), Stockholm, Sweden.
    Gillberg, Mats
    Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden.
    Vestergren, Peter
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    Sleepiness and sleep in a simulated ''six hours on/six hours off'' sea watch system2006In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 23, no 6, p. 1193-1202Article in journal (Refereed)
    Abstract [en]

    Ships are operated around the clock using rapidly rotating shift schedules called sea watch systems. Sea watch systems may cause fatigue, in the same way as other irregular working time arrangements. The present study investigated subjective sleepiness and sleep duration in connection with a 6 h on/6 h off duty system. The study was performed in a bridge simulator, very similar to those found on ships. Twelve officers divided into two groups participated in the study that lasted 66 h. Half of the subjects started with the 06:00-12:00 h watch and the other half with the 12:00-18:00 h watch. The subjects alternated between off-duty and on-duty for the remainder of the experimental period. Approximately halfway through the experiment, the 12:00-18: 00 h watch was divided into two 3 h watches/off-duty periods. The effect of this was to reverse the on-duty/off-duty pattern between the two groups. This enabled all subjects to work the four possible watches (00:00-06:00 h, 06:00-12:00 h, 12:00-18:00 h, and 18:00-24:00 h) in an order that was essentially counterbalanced between groups. Ratings of sleepiness (Karolinska Sleepiness Scale; KSS) were obtained every 30 min during on-duty periods and if subjects were awake during off-duty periods. The subjectively rated duration of sleep was recorded after each off-duty period that preceded watch periods when KSS was rated. The results showed that the average level of sleepiness was significantly higher during the 00:00-06:00 h watch compared to the 12:00-18:00 h and 18:00-24:00 h watches, but not to the 06:00-12:00 h watch. Sleepiness also progressed significantly from the start toward the end of each watch, with the exception of the 06:00-12:00 h watch, when levels remained approximately stable. There were no differences between groups (i.e., the order between watches). Sleep duration during the 06:00-12:00 h off-duty period (3 h 29 min) was significantly longer than during the 12:00-18:00 h period (1 h 47 min) and the 18:00-24:00 h period (2 h 7 min). Sleep during the 00:00-06:00 h period (4 h 23 min) was longer than all sleep periods except the 06:00-12:00 h period. There were no differences between groups. In spite of sufficient opportunities for sleep, sleep was on the average around 1-1 h 30 min shorter than the 7-7 h 30 min that is considered "normal" during a 24 h period. This is probably a consequence of the difficulty to sleep during daytime due to the alerting effects of the circadian rhythm. Also, sleepiness during the night and early mornings reached high levels, which may be explained by a combination of working close to or during the circadian trough of alertness and the relatively short sleep periods obtained. An initial suppression of sleepiness was observed during all watches, except for the 06:00-12:00 h watch. This suppression may be explained by the "masking effect" exerted by the relative high levels of activity required when taking over the responsibility of the ship. Toward the end of watches, the levels of sleepiness progressively increased to relatively high levels, at least during the 00:00-06:00 h watch. Presumably, initially high levels of activity are replaced by routine and even boredom.

  • 9.
    Inoue, Y.
    et al.
    University of Tokyo, Bunkyo-ku, Tokyo, Japan.
    Stickley, Andrew
    Södertörn University, School of Social Sciences, Sociology. Södertörn University, School of Social Sciences, SCOHOST (Stockholm Centre for Health and Social Change). University of Tokyo, Bunkyo-ku, Tokyo, Japan.
    Yazawa, A.
    University of Tokyo, Bunkyo-ku, Tokyo, Japan.
    Fujiwara, T.
    National Center for Child Health and Development, Setagaya-ku, Japan.
    Kondo, K.
    Chiba University, Chiba City, Chiba, Japan / Nihon Fukushi University, Nagoya City, Aichi, Japan.
    Kondo, N.
    University of Tokyo, Bunkyo-ku, Tokyo, Japan.
    Month of birth is associated with mortality among older people in Japan: Findings from the JAGES cohort2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 4, p. 441-447Article in journal (Refereed)
    Abstract [en]

    Month of birth (MOB) has been linked to a variety of health conditions in adulthood. This study examined the association between MOB and mortality among the healthy elderly in Japan, where a practice of traditional age reckoning was employed up until the late 1940s. The results showed male participants born in December were more likely to die earlier while those born in January had lower mortality. It is possible that social factors in early life, such as the time period when a birth is officially registered, may have implications for health that stretch across the life course.

  • 10.
    Kecklund, Göran
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Milia, Lee Di
    Axelsson, John
    Lowden, Arne
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    20th International Symposium on Shiftwork and Working Time: Biological Mechanisms, Recovery, and Risk Management in the 24-h Society2012In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 29, no 5, p. 531-536Article in journal (Refereed)
    Abstract [en]

    This dedicated issue of Chronobiology International is devoted to the selected proceedings of the 20th International Symposium on Shift Work and Working Time held in Stockholm, Sweden, 28 June to 1 July 2011. It constitutes the fifth such issue of the journal since 2004 dedicated to the selected proceedings to the meetings of the Working Time Society. The key theme of the 20th Symposium was "Biological Mechanisms, Recovery, and Risk Management in the 24-h Society." The collection of papers of this dedicated issue represents the best of contemporary research on the effects of night and rotating shift schedules on worker health and safety. The contents cover such topics as sleep restriction, injuries, health, and performance of night work and rotating shiftwork, plus light treatment as a countermeasure against the circadian disruption of shiftwork. The majority of the papers are observational field studies, including some of large sample size, and three studies are well-designed laboratory experiments. (Author correspondence: goran.kecklund@stress.su.se ).

  • 11.
    Keramidas, Michail E.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Siebenmann, Christoph
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Norrbrand, Lena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Gadefors, Magnus
    Mil Acad Karlberg, Stockholm, Sweden..
    Eiken, Ola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    A brief pre-exercise nap may alleviate physical performance impairments induced by short-term sustained operations with partial sleep deprivation - A field-based study2018In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 35, no 10, p. 1464-1470Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to evaluate the recuperative efficacy of pre-exercise napping on physical capacity after military sustained operations (SUSOPS) with partial sleep deprivation. Before and after a 2-day SUSOPS, 61 cadets completed a battery of questionnaires, and performed a 2-min lunges trial and a 3,000-m running time-trial. After the completion of SUSOPS, subjects were randomized to either a control [without pre-exercise nap (CON); n = 32] or a nap [with a 30-min pre-exercise nap (NAP); n = 29] group. SUSOPS enhanced perceived sleepiness and degraded mood in both groups. Following SUSOPS, the repetitions of lunges, in the CON group, were reduced by similar to 2.3%, albeit the difference was not statistically significant (p = 0.62). In the NAP group, however, the repetitions of lunges were increased by similar to 7.1% (p = 0.01). SUSOPS impaired the 3,000-m running performance in the CON group (similar to 2.3%; p = 0.02), but not in the NAP group (0.3%; p = 0.71). Present results indicate, therefore, that a relatively brief pre-exercise nap may mitigate physical performance impairments ensued by short-term SUSOPS.

  • 12.
    Khezri, Banafsheh Seyyed
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Cederblad, Maria
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Helmersson-Karlqvist, Johanna
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry.
    Karlsson, Bo
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences.
    Melhus, Håkan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Larsson, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry.
    Seasonal variability of NT-proBNP in Swedish primary care patients2017In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 34, no 10, p. 1473-1477Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to determine if there is a seasonal variation in the widely used heart failure marker NT-proBNP. The study included all primary care requests for NT-proBNP in the county of Uppsala, Sweden, between January 2007 and December 2015. For seasonal variation, the NT-proBNP results for individual months were compared. The NT-proBNP values were highest in July to September, but there was also a minor peak in December-January. In conclusion, a seasonal periodicity for NT-proBNP was demonstrated in primary care patients. The data could be useful for practitioners for evaluation of NT-proBNP results and monitoring of patients with heart failure.

  • 13.
    Knutsson, Anders
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Methodological aspects of shift-work research2004In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Chronobiology International, ISSN 0742-0528, Vol. 21, no 6, p. 1037-1047Article in journal (Refereed)
    Abstract [en]

    A major issue in shift-work research is to understand the possible ways in which shift work can impact performance and health. Nearly all body functions, from those of the cellular level to those of the entire body, are circadian rhythmic. Disturbances of these rhythms as well as the social consequences of odd work hours are of importance for the health and well-being of shift workers. This article reviews a number of common methodological issues which are of relevance to epidemiological studies in this area of research. It discusses conceptual problems regarding the use of the term "shift work," and it underscores the need to develop models that explain the mechanisms of disease in shift workers.

  • 14.
    Knutsson, Anders
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Hammar, Niklas
    Karlsson, Berndt
    Shift workers mortality scrutinized2004In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 21, no 6, p. 1049-1053Article in journal (Refereed)
    Abstract [en]

    The objective of this article is to reappraise previous published data on the mortality of male shift workers from Taylor and Pocock (1972). Mortality rate ratios were calculated for shift workers, ex-shift workers, and for shift workers plus ex-shift workers, respectively, compared to day workers using the Mantel-Haenszel method. The overall risk for current and former shift workers was 1.05 (95% Confidence Interval: 0.95-1.16). For ex-shift workers the mortality was increased compared to day workers (1.24, 95% Confidence Interval: 1.03-1.51). In the age specific analyses increased mortality was observed in shift workers compared with day workers in the age group of 45-54 yrs (Relative Risk: 1.47, 95% Confidence Interval: 1.12-1.93). We suggest that shift work is associated with increased mortality risk.

  • 15.
    Knutsson, Anders
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Kempe, Anders
    Health Centre of Söråker, Timrå, Sweden.
    Shift work and diabetes - A systematic review2014In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 31, no 10, p. 1146-1151Article, review/survey (Refereed)
    Abstract [en]

    Diabetes mellitus is a chronic disease, which has an increasing trend all over the world. Type 2 diabetes constitutes 90% of all diabetes. It is associated with weight gain and insulin resistance. Research during recent years has suggested that shift work could be a risk factor of type 2 diabetes. Since shift work is becoming more common, it could contribute to the increasing trend of diabetes. In this systematic review, we have studied the potential association between shift work and type 2 diabetes. We have also reviewed studies on control of diabetes in relation to shift work.

  • 16.
    Larsson, Anders
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry.
    Hassan, Moustapha
    2Experimental Cancer Medicine, KFC Novum, Karolinska University Hospital Huddinge,.
    Ridefelt, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Chemistry.
    Axelsson, John
    Section of Psychology, Department of Clinical Neurosciences, Karolinska Institutet,.
    Circadian variability of bilirubin in healthy men during normal sleep and after an acute shift of sleep2009In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 26, no 8, p. 1613-1621Article in journal (Refereed)
    Abstract [en]

    Bilirubin is a laboratory test widely used for patient care, especially neonatal patients and patients with anemia or suspected liver disorders. Bilirubin has also been shown to be associated with sleep pattern and oxidative stress. The aim of this study was to investigate the variation of bilirubin in a group of healthy individuals with normal night sleep as well as during acutely displaced sleep, as sleep timing varies immensely between individuals while clinical samples are still mainly taken in the morning. We studied the diurnal variation of bilirubin during night-sleep and day-sleep conditions in seven healthy volunteers. Serum samples were collected every hour (50 samples/individual) to evaluate the effect of different sampling times and sleep displacement on the test results. The mean acrophases (peak time) occurred at 10.6 h during the night-sleep condition and at 18.4 h during the day-sleep condition. The diurnal intraindividual variation was high during both the night-sleep and day-sleep conditions, with coefficients of variation (CV) in the range of 12.8 to 42.5%. The diurnal variation was higher during the day compared to night-sleep condition. Thus, bilirubin sampling should be restricted to the morning, preferably after a normal night sleep, to minimize intraindividual variation.

  • 17.
    Larsson, Anders
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Åkerstedt, Torbjörn
    Hansson, Lars-Olof
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Axelsson, John
    Circadian Variability of Cystatin C, Creatinine, and Glomerular Filtration Rate (GFR) in Healthy Men during Normal Sleep and after an Acute Shift of Sleep2008In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 25, no 6, p. 1047-61Article in journal (Refereed)
    Abstract [en]

    The estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with kidney disease and for the treatment of patients with medications that are eliminated by the kidneys. Plasma cystatin C has been shown in several studies to be superior to plasma creatinine for the estimation of GFR. However, there is limited information on the circadian variation of cystatin C and estimated GFR using cystatin C (eGFR(CystC)) or "The Modification of Diet in Renal Disease Study" (MDRD) (eGFR(MDRD)) equations. We studied the circadian variation of cystatin C and creatinine during night- and day-sleep conditions in seven healthy volunteers. Serum samples were collected every hour (48 samples per individual) to evaluate the effect of different sampling times on the test results. The median intra-individual coefficients of variations for the studied markers were 4.2% for creatinine, 4.7% for eGFR(MDRD), 5.5% for cystatin C, and 7.7% for eGFR(CystC). Neither cystatin C nor creatinine differed significantly between the night- and day-sleep conditions. Cystatin C differed significantly with time of day (p=.0003), but this was not the case for creatinine (p=.11). The circadian variation of cystatin C was minor. Small but significant increases in creatinine values and a decrease of eGFR(MDRD) were observed after food intake. Thus, cystatin C and creatinine sampling does not have to be restricted to specific times of the day.

  • 18.
    Lowden, Arne
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Karolinska Institute, Sweden.
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Karolinska Institute, Sweden.
    Assessment of a new dynamic light regimen in a nuclear power control room without windows on quickly rotating shiftworkers-effects on health, wakefulness, and circadian alignment: a pilot study2012In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 29, no 5, p. 641-649Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to test whether a new dynamic light regime would improve alertness, sleep, and adaptation to rotating shiftwork. The illumination level in a control room without windows at a nuclear power station was ∼200 lux (straight-forward horizontal gaze) using a weak yellow light of 200 lux, 3000 K (Philips Master TLD 36 W 830). New lighting equipment was installed in one area of the control room above the positions of the reactor operators. The new lights were shielded from the control group by a distance of >6 m, and the other operators worked at desks turned away from the new light. The new lights were designed to give three different light exposures: (i) white/blue strong light of 745 lux, 6000 K; (ii) weak yellow light of 650 lux, 4000 K; and (iii) yellow moderate light of 700 lux, 4000 K. In a crossover design, the normal and new light exposures were given during a sequence of three night shifts, two free days, two morning shifts, and one afternoon shift (NNN + MMA), with 7 wks between sessions. The operators consisted of two groups; seven reactor operators from seven work teams were at one time exposed to the new equipment and 16 other operators were used as controls. The study was conducted during winter with reduced opportunities of daylight exposure during work, after night work, or before morning work. Operators wore actigraphs, filled in a sleep/wake diary, including ratings of sleepiness on the Karolinska Sleepiness Scale (KSS) every 2 h, and provided saliva samples for analysis of melatonin at work (every 2nd h during one night shift and first 3 h during one morning shift). Results from the wake/sleep diary showed the new light treatment increased alertness during the 2nd night shift (interaction group × light × time, p < .01). Time of waking was delayed in the light condition after the 3rd night shift (group × light, p < .05), but the amount of wake time during the sleep span increased after the 2nd night shift (p < .05), also showing a tendency to affect sleep efficiency (p < .10). Effects on circadian phase were difficult to establish given the small sample size and infrequent sampling of saliva melatonin. Nonetheless, it seems that appropriate dynamic light in rooms without windows during the dark Nordic season may promote alertness, sleep, and better adaptation to quickly rotating shiftwork. (Author correspondence: arne.lowden@stress.su.se ).

  • 19.
    Matthews, Raymond W.
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Central Queensland University, Australia; Karolinska Institute, Sweden.
    Kontou, Thomas G.
    Naweed, Anjum
    Sargent, Charli
    Roach, Gregory D.
    Driving when distracted and sleepy: The effect of phone and passenger conversations on driving performance2018In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 35, no 6, p. 750-753Article in journal (Refereed)
    Abstract [en]

    This study investigates the effect of passenger and phone conversations on sleep-restricted driving. Six volunteers (50% male, mean age 24.8 +/- 4.3years) had their sleep restricted to 4h in bed followed by a 20-min simulated drive on three separate occasions. Each drive included either a passenger conversation, a mobile phone conversation or a quiet passenger. The effect size of a phone conversation on lane deviation was large while passenger conversation was small. The main effect of conversation on lane deviation was non-significant (F(2,10)=2.57, p=0.126). Combining sleep-restricted driving with conversations warrants further investigation.

  • 20.
    Moreno, Claudia R. C.
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. University of São Paulo, Brazil.
    Lowden, Arne
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Vasconcelos, Suleima
    Marqueze, Elaine C.
    Musculoskeletal pain and insomnia among workers with different occupations and working hours2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 6, p. 749-753Article in journal (Refereed)
    Abstract [en]

    Several studies have shown a bidirectional relationship between insomnia and pain. The aim of this study was to evaluate whether working hours and type of occupation are associated with insomnia, pain and insomnia plus pain. Insomnia and musculoskeletal pain symptoms were measured in airline pilots, rural workers and factory workers using validated indexes. Rural and night work were predictors for the outcomes (insomnia and pain). However, musculoskeletal pain was found to be a predictor of insomnia but not vice versa. The current findings suggest that working hours and type of occupation play a role in the sleep-pain relationship.

  • 21. Ordookhani, Arash
    et al.
    Padyab, Mojgan
    Endocrine Research Center, Taleghani Hospital, Shaheed Beheshti University of Medical Sciences, Tehran, Iran.
    Goldasteh, Akbar
    Mirmiran, Parvin
    Richter, Jörg
    Azizi, Fereidoun
    Seasonal variation of neonatal transient hyperthyrotropinemia in tehran province, 1998–20052010In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 27, no 9-10, p. 1854-1869Article in journal (Refereed)
    Abstract [en]

    Seasonal aggregation and the monthly rate of neonatal transient hyperthyrotropinemia(THT) were assessed. From November 1998 to April 2005, neonates of gestationalage ≥37 wks, birth weight 2500–4000 g, birth length 45–55 cm, and 1st min Apgarscore >3, who had thyrotropin (TSH) ≥20 mU/L in their cord dried-blood specimen,but without congenital hypothyroidism, were enrolled in the study. The recall rateequals the rate of THT occurrence in this study. Of 47,945 neonates, 555 had THT(recall rate: 1.2%). The aggregated seasonal recall rate (recall for further assessment torule out congenital hypothyroidism) was significantly higher in winter (January,February, and March) than the other seasons ( p < .0001). Winter had higher recallrate in each year as compared to other seasons, but the overall rate of recalls decreasedin 2001 and 2002. Excluding the first 6 months (due to erratic variations), the remaining72 months revealed a relatively sinusoidal pattern in monthly recall rates; indeed,there was an initial 11-month high recall rates (1.7%), followed by a 33-month decrease(0.7%), a 19-month increase (1.9%), and a final 9-month decrease (0.8%). The recallrate of each of these time intervals was significantly different from that of the nexttime interval ( p < .0001). The monthly recall rates were best fitted to cubic curve estimationand then autoregressive integrated moving average (ARIMA) (0, 1, 1) models.THT occurs significantly more in winter than in other seasons, and this suggests apossible role for time-varying factor(s) contributing to its seasonal preponderance.

  • 22. Pereira de Holanda, Narriane Chaves
    et al.
    de Castro Moreno, Claudia Roberta
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. University of São Paulo, Brazil.
    Marqueze, Elaine Cristina
    Metabolic syndrome components: Is there a difference according to exposure to night work?2018In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 35, no 6, p. 801-810Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare metabolic aspects potentially associated with metabolic syndrome (MetS), in addition to serum leptin levels and sleep, according to exposure to night work among nursing staff. A cross-sectional study involving 60 nursing staff was conducted. Sociodemographic, sleep (Karolinska Sleep Questionnaire), physical activity (International Physical Activity Questionnaire), and nutrition data (16-Food Intake Questionnaire) were collected. Body measurements and blood pressure were taken and blood collected to determine glycemia, total cholesterol and portions of low-density lipoprotein and high-density lipoprotein and triglycerides, and leptin levels. The sample was divided into three groups according to exposure to night work (nonexposed, currently exposed, past exposure). Furthermore, to evaluate the relationship between exposure time and prevalence of MetS, the night-exposed groups (past and current) were divided according to time exposed to night shifts (<10 years and >= 10 years). Mean age of participants was 39.8 +/- 10.5 years. The groups were homogenous with regard to sociodemographic characteristics, physical activity, dietary patterns, and health aspects. The prevalence of MetS in the population studied was 32%, above the rate for the general population. However, there were no significant differences among the groups. In addition, a higher proportion of participants with hypertriglyceridemia and diastolic arterial hypertension was observed in the currently exposed group. The currently exposed group also reported less sleep and higher sleep debt than the other groups on workdays. Although no differences were observed among the groups regarding MetS, the currently exposed group had more sleep disturbances than the others, and a higher prevalence of two out of three risk factors for the MetS diagnosis.

  • 23.
    Persson, Roger
    et al.
    National Research Centre of Working Environment, Denmark.
    Helene Garde, Anne
    National Research Centre of Working Environment, Denmark.
    Marie Hansen, Ase
    National Research Centre of Working Environment, Denmark.
    Osterberg, Kai
    Lund University.
    Larsson, Britt
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Rehabilitation Medicine . Östergötlands Läns Landsting, Centre for Medicine, Pain and Rehabilitation Centre.
    Orbaek, Palle
    National Research Centre of Working Environment, Denmark.
    Karlson, Bjorn
    Lund University.
    Seasonal Variation in Human Salivary Cortisol Concentration2008In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 25, no 6, p. 923-937Article in journal (Refereed)
    Abstract [en]

    Measurement of cortisol concentration can contribute important information about an individuals ability to adjust to various environmental demands of both physical and psychosocial origin. However, one uncertainty that affects the possibilities of correctly interpreting and designing field studies is the lack of observations of the impact of seasonal changes on cortisol excretion. For this reason, the month-to-month changes in diurnal cortisol concentration, the awakening cortisol response (ACR), maximum morning concentration, and fall during the day were studied in a group of 24 healthy men and women 32 to 61 yrs of age engaged in active work. On one workday for 12 consecutive months, participants collected saliva at four time points for determination of cortisol: at awakening, +30min, +8h, and at 21:00h. Data were analyzed by a repeated measures design with month (12 levels) and time-of-day (4 levels) as categorical predictors. Cortisol concentrations were analyzed on a log scale. The diurnal pattern of cortisol was similar across months (interaction between month and time of day: p0.4). The main effects of month and time-of-day were statistically significant (p0.001). Highest concentrations were observed in February, March, and April, and lowest concentrations were observed in July and August. There were no statistically significant effects in any of the other measures, or between men and women. In conclusion, a seasonal variation in salivary cortisol concentrations was detected in an occupationally active population. Thus, seasonal variation needs to be taken into account when designing and evaluating field studies and interventions and when making comparisons across studies.

  • 24. Roach, Gregory D.
    et al.
    Matthews, Raymond
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Central Queensland University, Sweden; Karolinska Institute, Sweden.
    Naweed, Anjum
    Kontou, Thomas G.
    Sargent, Charli
    Flat-out napping: The quantity and quality of sleep obtained in a seat during the daytime increase as the angle of recline of the seat increases2018In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 35, no 6, p. 872-883Article in journal (Refereed)
    Abstract [en]

    Some shiftwokers in the long-haul transportation industries (i.e. road, rail, sea, air) have the opportunity to sleep in on-board rest facilities during duty periods. These rest facilities are typically fitted with a seat with a maximum back angle to the vertical of 20 degrees, 40 degrees, or 90 degrees. The aim of this study was to examine the impact of back angle on the quantity and quality of sleep obtained in a seat during a daytime nap. Six healthy adults (3 females aged 27.0 years and 3 males aged 22.7 years) each participated in three conditions. For each condition, participants had a 4-h sleep opportunity in a bed (02:00-06:00 h) followed by a 4-h sleep opportunity in a seat (13:00-17:00 h). The only difference between conditions was in the back angle of the seat to the vertical during the seat-based sleep periods: 20 degrees (upright), 40 degrees (reclined), and 90 degrees (flat). Polysomnographic data were collected during all sleep episodes. For the seat-based sleep episodes, there was a significant effect of back angle on three of four measures of sleep quantity, i.e. total sleep time, slow-wave sleep, and rapid eye movement (REM) sleep, and three of four measures of sleep quality, i.e. latency to REM sleep, arousals, and stage shifts. In general, the quantity and quality of sleep obtained in the reclined and flat seats were better than those obtained in the upright seat. In particular, compared to the flat seat, the reclined seat resulted in similar amounts of total sleep and slow-wave sleep, but 37% less REM sleep; and the upright seat resulted in 29% less total sleep, 30% less slow-wave sleep, and 79% less REM sleep. There are two main mechanisms that may explain the results. First, it is difficult to maintain the head in a comfortable position for sleep when sitting upright, and this is likely exacerbated during REM sleep, when muscle tone is very low. Second, an upright posture increases sympathetic activity and decreases parasympathetic activity, resulting in a heightened level of physiological arousal.

  • 25. Thomas, Matthew J. W.
    et al.
    Paterson, Jessica L.
    Jay, Sarah M.
    Matthews, Raymond W.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Central Queensland University, Australia; Karolinska Institute, Sweden.
    Ferguson, Sally A.
    More than hours of work: fatigue management during high-intensity maritime operations2019In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 36, no 1, p. 143-149Article in journal (Refereed)
    Abstract [en]

    Objectives: This study examines the impacts of peak summer demand on operator workload and fatigue in a maritime environment. Methods: Participants (n = 12) were senior shipboard personnel who were working during the summer double sailing period for a roll-on roll-off ferry service. Wrist actigraphy was used to determine sleep opportunity and sleep duration, as well as prior sleep, total wake time, performance and alertness at the beginning and end of work periods. Results: Contrary to expectations, sleep was significantly greater, and both subjective estimates of fatigue and objective neurobehavioral performance were not impacted negatively by periods of increased work intensity. Conclusions: This study highlights a number of features of a fatigue-risk management system that appear to have been instrumental in ensuring adequate sleep and performance was maintained throughout periods of increased operational intensity. As a simple colloquial description of the fatigue-risk management system at play in this operation, it was fine to work hard if you were able to sleep hard as well.

  • 26. Thun, Eirunn
    et al.
    Bjorvatn, Bjørn
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Moen, Bente Elisabeth
    Waage, Siri
    Molde, Helge
    Pallesen, Ståle
    Trajectories of sleepiness and insomnia symptoms in Norwegian nurses with and without night work and rotational work2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 5, p. 480-489Article in journal (Refereed)
    Abstract [en]

    Numerous cross-sectional studies report high prevalence rates of sleepiness and insomnia in shift workers, but few longitudinal studies exist. We investigated trajectories of sleepiness and insomnia symptoms in a sample of Norwegian nurses across four measurements, spanning a total of four years (sleepiness) and five years (insomnia). The participants completed the Epworth Sleepiness Scale and the Bergen Insomnia Scale at each measurement instance. Latent growth curve models were used to analyse the data. Separate models examined night work (night work, entering and leaving night work) and rotational work (rotational work, entering and leaving rotational work) as predictors for trajectories of sleepiness and insomnia symptoms, respectively. Baseline values of sleepiness and insomnia were higher among rotational shift workers than among workers with fixed shifts (day or night). The results showed that night work throughout the period and entering night work during the period were not associated with different trajectories of sleepiness or insomnia symptoms, compared to not having night work. The same results were found for rotational work and entering rotational work, compared to not having rotational work. Leaving night work and leaving rotational work were associated with a decrease in sleepiness and insomnia symptoms, compared to staying in such work.

  • 27.
    Tucker, Philip
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. Swansea University, United Kingdom.
    Albrecht, Sophie
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Beckers, Debby G. J.
    Leineweber, Constanze
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Work time control, sleep & accident risk: A prospective cohort study2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 6, p. 619-629Article in journal (Refereed)
    Abstract [en]

    We examined whether the beneficial impact of work time control (WTC) on sleep leads to lower accident risk, using data from a nationally representative survey conducted in Sweden. Logistic regressions examined WTC in 2010 and 2012 as predictors of accidents occurring in the subsequent 2 years (N = 4840 and 4337, respectively). Sleep disturbance and frequency of short sleeps in 2012 were examined as potential mediators of the associations between WTC in 2010 and subsequent accidents as reported in 2014 (N = 3636). All analyses adjusted for age, sex, education, occupational category, weekly work hours, shift work status, job control and perceived accident risk at work. In both waves, overall WTC was inversely associated with accidents (p = 0.048 and p = 0.038, respectively). Analyses of the sub-dimensions of WTC indicated that Control over Daily Hours (influence over start and finish times, and over length of shift) did not predict accidents in either wave, while Control over Time-off (CoT; influence over taking breaks, running private errands during work and taking paid leave) predicted fewer accidents in both waves (p = 0.013 and p = 0.010). Sleep disturbance in 2012 mediated associations between WTC/CoT in 2010 and accidents in 2014, although effects' sizes were small (effectWTC = -0.006, 95% confidence interval [CI] = -0.018 to -0.001; effectCoT = -0.009, 95%CI = -0.022 to -0.001; unstandardized coefficients), with the indirect effects of sleep disturbance accounting for less than 5% of the total direct and indirect effects. Frequency of short sleeps was not a significant mediator. WTC reduces the risk of subsequently being involved in an accident, although sleep may not be a strong component of the mechanism underlying this association.

  • 28. Uluoglu, C
    et al.
    Durakoglugil, D B
    Karasu, C
    Ozbey, G
    Gunes, A
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Zengil, H
    The effect of experimental diabetes on the twenty-four-hour pattern of the vasodilator responses to acetylcholine and isoprenaline in the rat aorta.2007In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 24, no 6, p. 1081-1094Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate whether time-dependent variations in the relaxant effect of acetylcholine, an endothelium-dependent vasorelaxant via muscarinic receptors, and isoprenaline, a nonselective β-adrenoceptor agonist in rat aorta, are influenced by streptozotocin (STZ)-induced experimental diabetes. Adult male rats were divided randomly into two groups: control and STZ-induced (STZ, 55 mg/kg, intraperitoneal) diabetes. The animals were synchronized to a 12:12 h light-dark cycle (lights on 08:00 h) and sacrificed at six different times of day (1, 5, 9, 13, 17, and 21 hours after lights on; HALO) eight weeks after STZ injection. The in vitro responsiveness of thoracic aorta rings obtained from control and diabetic rats to acetylcholine (10-9-10-5 M) and isoprenaline (10-10-10-3 M) was determined in six different times. EC50 (the concentration inducing half of the maximum response) values and maximum responses were calculated from cumulative concentration-response curves of the agonists and were analyzed with respect to time and STZ treatment. Treatment, time, and interactions between treatment and time were tested by two-way analysis of variance (ANOVA). To analyze differences due to biological time, one-way ANOVA was used. STZ treatment did not significantly change EC50 values or maximum responses for both agonists. There were statistically significant time-dependent variations in the EC50 values for isoprenaline and maximum responses for both acetylcholine and isoprenaline in control groups by one-way ANOVA, but significant time-dependent variations disappeared in the aortas isolated from STZ-induced diabetic rats. The vasodilator responses to acetylcholine and isoprenaline failed to show any significant interaction (treatmenttime of study) between STZ treatment and time of sacrifice in both EC50 values and maximum responses by two-way ANOVA. These results indicate there is a basic temporal pattern in the responses to acetylcholine and isoprenaline in rat aorta which continues in diabetes. It is shown for the first time that experimental diabetes does not change the 24 h pattern of responses to acetylcholine and isoprenaline, and that time-dependent variations in the responses to these agonists disappear in diabetic animals. Although further studies are required to define the underlying mechanism(s) of these findings, results suggest that experimental diabetes can modify the time-dependent vasorelaxant responses of rat aorta. This may help to understand the circadian rhythms in cardiovascular physiology and pathology or in drug effects in diabetes.

  • 29.
    van Leeuwen, Wessel M. A.
    et al.
    Stockholm University, Sweden .
    Kircher, Albert
    Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Dahlgren, Anna
    KTH Royal Institute of Technology, Sweden.
    Lutzhoft, Margareta
    Chalmers University of Technology, Gothenburg, Sweden.
    Barnett, Mike
    Southampton Solent University, UK.
    Kecklund, Goran
    Stockholm University, Sweden .
    Åkerstedt, Torbjörn
    Stockholm University, Sweden .
    Sleep, Sleepiness, and Neurobehavioral Performance While on Watch in a Simulated 4 Hours on/8 Hours off Maritime Watch System2013In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 30, no 9, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Seafarer sleepiness jeopardizes safety at sea and has been documented as a direct or contributing factor in many maritime accidents. This study investigates sleep, sleepiness, and neurobehavioral performance in a simulated 4 h on/8 h off watch system as well as the effects of a single free watch disturbance, simulating a condition of overtime work, resulting in 16 h of work in a row and a missed sleep opportunity. Thirty bridge officers (age 30 +/- 6 yrs; 29 men) participated in bridge simulator trials on an identical 1-wk voyage in the North Sea and English Channel. The three watch teams started respectively with the 00-04, the 04-08, and the 08-12 watches. Participants rated their sleepiness every hour (Karolinska Sleepiness Scale [KSS]) and carried out a 5-min psychomotor vigilance test (PVT) test at the start and end of every watch. Polysomnography (PSG) was recorded during 6 watches in the first and the second half of the week. KSS was higher during the first (mean +/- SD: 4.0 +/- 0.2) compared with the second (3.3 +/- 0.2) watch of the day (p andlt; 0.001). In addition, it increased with hours on watch (p andlt; 0.001), peaking at the end of watch (4.1 +/- 0.2). The free watch disturbance increased KSS profoundly (p andlt; 0.001): from 4.2 +/- 0.2 to 6.5 +/- 0.3. PVT reaction times were slower during the first (290 +/- 6 ms) compared with the second (280 +/- 6 ms) watch of the day (p andlt; 0.001) as well as at the end of the watch (289 +/- 6 ms) compared with the start (281 +/- 6 ms; p = 0.001). The free watch disturbance increased reaction times (p andlt; 0.001) from 283 +/- 5 to 306 +/- 7 ms. Similar effects were observed for PVT lapses. One third of all participants slept during at least one of the PSG watches. Sleep on watch was most abundant in the team working 00-04 and it increased following the free watch disturbance. This study reveals that-within a 4 h on/8 h off shift system-subjective and objective sleepiness peak during the night and early morning watches, coinciding with a time frame in which relatively many maritime accidents occur. In addition, we showed that overtime work strongly increases sleepiness. Finally, a striking amount of participants fell asleep while on duty.

  • 30. van Leeuwen, Wessel M. A.
    et al.
    Kircher, Albert
    Dahlgren, Anna
    KTH, School of Technology and Health (STH), Health Systems Engineering, Systems Safety and Management.
    Lützhöft, Margareta
    Barnett, Mike
    Kecklund, Göran
    Åkerstedt, Torbjörn
    Sleep, Sleepiness, and Neurobehavioral Performance While on Watch in a Simulated 4 Hours on/8 Hours off Maritime Watch System2013In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 30, no 9, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Seafarer sleepiness jeopardizes safety at sea and has been documented as a direct or contributing factor in many maritime accidents. This study investigates sleep, sleepiness, and neurobehavioral performance in a simulated 4 h on/8 h off watch system as well as the effects of a single free watch disturbance, simulating a condition of overtime work, resulting in 16 h of work in a row and a missed sleep opportunity. Thirty bridge officers (age 30 +/- 6 yrs; 29 men) participated in bridge simulator trials on an identical 1-wk voyage in the North Sea and English Channel. The three watch teams started respectively with the 00-04, the 04-08, and the 08-12 watches. Participants rated their sleepiness every hour (Karolinska Sleepiness Scale [KSS]) and carried out a 5-min psychomotor vigilance test (PVT) test at the start and end of every watch. Polysomnography (PSG) was recorded during 6 watches in the first and the second half of the week. KSS was higher during the first (mean +/- SD: 4.0 +/- 0.2) compared with the second (3.3 +/- 0.2) watch of the day (p < 0.001). In addition, it increased with hours on watch (p < 0.001), peaking at the end of watch (4.1 +/- 0.2). The free watch disturbance increased KSS profoundly (p < 0.001): from 4.2 +/- 0.2 to 6.5 +/- 0.3. PVT reaction times were slower during the first (290 +/- 6 ms) compared with the second (280 +/- 6 ms) watch of the day (p < 0.001) as well as at the end of the watch (289 +/- 6 ms) compared with the start (281 +/- 6 ms; p = 0.001). The free watch disturbance increased reaction times (p < 0.001) from 283 +/- 5 to 306 +/- 7 ms. Similar effects were observed for PVT lapses. One third of all participants slept during at least one of the PSG watches. Sleep on watch was most abundant in the team working 00-04 and it increased following the free watch disturbance. This study reveals that-within a 4 h on/8 h off shift system-subjective and objective sleepiness peak during the night and early morning watches, coinciding with a time frame in which relatively many maritime accidents occur. In addition, we showed that overtime work strongly increases sleepiness. Finally, a striking amount of participants fell asleep while on duty.

  • 31.
    van Leeuwen, Wessel M A
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Kircher, Albert
    Dahlgren, Anna
    Lützhöft, Margareta
    Barnett, Mike
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Åkerstedt, Torbjörn
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Sleep, Sleepiness, and Neurobehavioral Performance While on Watch in a Simulated 4 Hours on/8 Hours off Maritime Watch System2013In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 30, no 9, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Seafarer sleepiness jeopardizes safety at sea and has been documented as a direct or contributing factor in many maritime accidents. This study investigates sleep, sleepiness, and neurobehavioral performance in a simulated 4 h on/8 h off watch system as well as the effects of a single free watch disturbance, simulating a condition of overtime work, resulting in 16 h of work in a row and a missed sleep opportunity. Thirty bridge officers (age 30 ± 6 yrs; 29 men) participated in bridge simulator trials on an identical 1-wk voyage in the North Sea and English Channel. The three watch teams started respectively with the 00-04, the 04-08, and the 08-12 watches. Participants rated their sleepiness every hour (Karolinska Sleepiness Scale [KSS]) and carried out a 5-min psychomotor vigilance test (PVT) test at the start and end of every watch. Polysomnography (PSG) was recorded during 6 watches in the first and the second half of the week. KSS was higher during the first (mean ± SD: 4.0 ± 0.2) compared with the second (3.3 ± 0.2) watch of the day (p < 0.001). In addition, it increased with hours on watch (p < 0.001), peaking at the end of watch (4.1 ± 0.2). The free watch disturbance increased KSS profoundly (p < 0.001): from 4.2 ± 0.2 to 6.5 ± 0.3. PVT reaction times were slower during the first (290 ± 6 ms) compared with the second (280 ± 6 ms) watch of the day (p < 0.001) as well as at the end of the watch (289 ± 6 ms) compared with the start (281 ± 6 ms; p = 0.001). The free watch disturbance increased reaction times (p < 0.001) from 283 ± 5 to 306 ± 7 ms. Similar effects were observed for PVT lapses. One third of all participants slept during at least one of the PSG watches. Sleep on watch was most abundant in the team working 00-04 and it increased following the free watch disturbance. This study reveals that-within a 4 h on/8 h off shift system-subjective and objective sleepiness peak during the night and early morning watches, coinciding with a time frame in which relatively many maritime accidents occur. In addition, we showed that overtime work strongly increases sleepiness. Finally, a striking amount of participants fell asleep while on duty.

  • 32.
    Wey, Daniela
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. São Paulo University, Brazil; Faculdades Metropolitanas Unidas, Brazil.
    Garefelt, Johanna
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Fischer, Frida M.
    Moreno, Claudia R.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute. São Paulo University, Brazil.
    Lowden, Arne
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Individual differences in the sleep/wake cycle of Arctic flexitime workers2016In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 33, no 10, p. 1422-1432Article in journal (Refereed)
    Abstract [en]

    Daytime workers tend to have shorter sleep duration and earlier sleep onset during work days than on days off. Large individual differences in sleep onset and sleep duration may be observed on work days, but work usually synchronizes sleep offset to a similar time. The present study describes individual differences in sleep behaviour of 48 daytime workers (25 men, aged 20-58 years) from an iron ore mine in Northern Sweden. The aim of the study was to determine whether differences in sleep patterns during work days were associated with the outcomes of sleepiness and sleep complaints. Cluster analysis was used to group workers into two categories of sleep onset and sleep duration. The "Late Sleep Onset" cluster comprised workers who slept 1.30 h later than the "Early Sleep Onset" cluster (p < 0.0001 for all weekdays). The "Long Sleep Duration" cluster slept 1.10 h longer than the "Short Sleep Duration" cluster (p < 0.0002 for work nights). The "Late Sleep Onset" cluster reported less refreshing sleep (p < 0.01) and had lower sufficient sleep scores (p < 0.01) than the "Early Sleep Onset" cluster. The "Short Sleep Duration" cluster also reported lower scores for sufficient sleep (p < 0.04) than the "Long Sleep Duration" cluster. For combined characteristics (phase and duration), workers with a late phase and short sleep duration reported greater sleep debt and sleepiness than workers with an early phase and short sleep duration (p < 0.02). Work schedule and commuting time modulate both sleep phase and sleep duration independently. Workers, classified as having an intermediate sleep phase preference, can organize their sleep time in order to minimize sleep debt and sleepiness symptoms. Individual differences in sleep phase and duration should be considered when promoting well-being at work even among groups with similar sleep needs. In order to minimize sleep debt and sleepiness symptoms, successful sleep behaviour could be promoted involving extend use of flexitime arrangement (i.e. later starting times) and reduce use of alarm clocks.

  • 33. Åkerstedt, Torbjorn
    et al.
    Nordin, Maria
    Alfredsson, Lars
    Westerholm, Peter
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Occupational and Environmental Medicine.
    Kecklund, Goran
    Sleep and sleepiness: impact of entering or leaving shiftwork - a prospective study2010In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 27, no 5, p. 987-996Article in journal (Refereed)
    Abstract [en]

    Very little is known about the effects on sleep and sleepiness of entering or exiting shift-work. The present study used a longitudinal database (n = 3637). Participants completed a questionnaire on work hours, sleep, and work environment at the start and end of a 5-yr period. Changes in shift/day work status were related to change in a number of subjective sleep variables using logistic regression analysis. The analyses were adjusted for age, sex, and differences in socioeconomic status, work demands, work control, physical workload, marriage status, and number of children. In comparison with constant day work, entering shiftwork (with or without night shifts) from day work increased the risk of difficulties in falling asleep, and leaving shiftwork reduced this risk (odds ratio [OR] = 2.8 [confidence interval, CI = 1.8-4.5]). Also falling asleep at work showed a consistent pattern; an increased risk of falling asleep for those with shiftwork on both occasions, and for those with night work on both occasions. Also entering night work was associated with a strongly increased risk of falling asleep at work (OR = 2.9 [CI = 1.3-6.7]). These results suggest that entering and leaving shiftwork has a considerable impact on sleep and alertness. However, there is a need for large and more extended longitudinal studies to support our findings. (Author correspondence: Torbjorn.akerstedt@ki.se)

  • 34. Åkerstedt, Torbjörn
    et al.
    Ingre, Michael
    Broman, Jan-Erik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience, Psychiatry, University Hospital.
    Kecklund, Göran
    Disturbed sleep in shift workers, day workers, and insomniacs2008In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 25, no 2-3, p. 333-348Article in journal (Refereed)
    Abstract [en]

    Very little is known about differences in sleep between day and shift workers in representative samples of the population. This study compared a national representative sample (N=3400) of shift (with night shifts) and day workers regarding the different types of sleep disturbances and also the level of sleep symptoms with that of insomnia patients. The results showed very few differences between shift and day workers; only too little sleep and nodding off at work were marginally higher among shift workers. The results also showed that the complaints of insomnia patients for most sleep disturbances corresponded to the 2nd-16th percentile of the shift workers' levels of complaints. The results suggest, at least with the present questionnaire methodology, that shift work does not appear to be a major source of sleep disturbances and that their complaint levels bear no resemblance to those seen in insomniac patients.

  • 35.
    Åkerstedt, Torbjörn
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Selén, Jan
    Early morning work--prevalence and relation to sleep/wake problems: a national representative survey.2010In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 27, no 5, p. 975-86Article in journal (Refereed)
    Abstract [en]

    Very little is known about the prevalence of morning work and its relationship with sleep and fatigue. The present study obtained data from a representative sample of the Swedish population (N = 5489) to address this limitation in the literature. The results show that 15% of the population commenced work, at least occasionally, before 05:30 h and approximately 2% did so most of the time. With the increasing phase advance of the start time, the time of rising also advanced, but bedtime changed very little. Thus, early start times were not compensated with earlier bedtimes. Total sleep time decreased as the work start time was advanced; sleep duration was <5 h for work start times between 03:00 and 04:30 h. The results also indicated that advanced start times were linked with increased fatigue, feelings of not being well rested, and reports of early start times as a rather large or very large problem. However, difficulties in waking and disturbed sleep did not change with advanced start times. It was concluded that early start times are common and are associated with sleep problems and fatigue.

  • 36.
    Åkerstedt, Torbjörn
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Nordin, Maria
    Alfredsson, Lars
    Westerholm, Peter
    Kecklund, Göran
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Sleep and sleepiness: impact of entering or leaving shiftwork--a prospective study.2010In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 27, no 5, p. 987-96Article in journal (Refereed)
    Abstract [en]

    Very little is known about the effects on sleep and sleepiness of entering or exiting shiftwork. The present study used a longitudinal database (n = 3637). Participants completed a questionnaire on work hours, sleep, and work environment at the start and end of a 5-yr period. Changes in shift/day work status were related to change in a number of subjective sleep variables using logistic regression analysis. The analyses were adjusted for age, sex, and differences in socioeconomic status, work demands, work control, physical workload, marriage status, and number of children. In comparison with constant day work, entering shiftwork (with or without night shifts) from day work increased the risk of difficulties in falling asleep, and leaving shiftwork reduced this risk (odds ratio [OR] = 2.8 [confidence interval, CI = 1.8-4.5]). Also falling asleep at work showed a consistent pattern; an increased risk of falling asleep for those with shiftwork on both occasions, and for those with night work on both occasions. Also entering night work was associated with a strongly increased risk of falling asleep at work (OR = 2.9 [CI = 1.3-6.7]). These results suggest that entering and leaving shiftwork has a considerable impact on sleep and alertness. However, there is a need for large and more extended longitudinal studies to support our findings.

  • 37. Åkerstedt, Torbjörn
    et al.
    Nordin, Maria
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Alfredsson, Lars
    Westerholm, Peter
    Kecklund, Göran
    Sleep and sleepiness: impact of entering or leaving shiftwork--a prospective study.2010In: Chronobiology International, ISSN 0742-0528, E-ISSN 1525-6073, Vol. 27, no 5, p. 987-996Article in journal (Refereed)
    Abstract [en]

    Very little is known about the effects on sleep and sleepiness of entering or exiting shiftwork. The present study used a longitudinal database (n = 3637). Participants completed a questionnaire on work hours, sleep, and work environment at the start and end of a 5-yr period. Changes in shift/day work status were related to change in a number of subjective sleep variables using logistic regression analysis. The analyses were adjusted for age, sex, and differences in socioeconomic status, work demands, work control, physical workload, marriage status, and number of children. In comparison with constant day work, entering shiftwork (with or without night shifts) from day work increased the risk of difficulties in falling asleep, and leaving shiftwork reduced this risk (odds ratio [OR] = 2.8 [confidence interval, CI = 1.8-4.5]). Also falling asleep at work showed a consistent pattern; an increased risk of falling asleep for those with shiftwork on both occasions, and for those with night work on both occasions. Also entering night work was associated with a strongly increased risk of falling asleep at work (OR = 2.9 [CI = 1.3-6.7]). These results suggest that entering and leaving shiftwork has a considerable impact on sleep and alertness. However, there is a need for large and more extended longitudinal studies to support our findings.

1 - 37 of 37
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