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  • 1.
    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.

  • 2. Hillvesson, F.
    et al.
    Lindholm, S.
    Vestergren, Peter
    Neurotec/Psychiatry, Karolinska Institutet, Karolinska University Hospital, Huddinge, Sweden.
    Hetta, J.
    SLEEP PROBLEMS RELATED TO PAST DEPRESSION AMONG PSYCHIATRISTS2004In: Abstracts of the ESRS, Prague 2004, 2004Conference paper (Refereed)
  • 3. Ingre, M.
    et al.
    Kecklund, G.
    Vestergren, Peter
    Karolinska Inst, S-10401 Stockholm, Sweden .
    Akerstedt, T.
    Kecklund, L.
    Early morning shifts (short sleep) and long distance between stops increase sleepiness in train-drivers2003Conference paper (Refereed)
  • 4.
    Kaida, Kaida
    et al.
    Stress Research Institute, Stockholm University.
    Åkerstedt, Torbjörn
    Stress Research Institute, Stockholm University.
    Takahashi, Masaya
    National Institute of Occupational Safety and Health (JNIOSH), Kawasaki, Japan.
    Vestergren, Peter
    Stress Research Institute, Stockholm University.
    Gillberg, Mats
    Stress Research Institute, Stockholm University.
    Lowden, Arne
    Stress Research Institute, Stockholm University.
    Kecklund, Göran
    Stress Research Institute, Stockholm University.
    Portin, Christian
    Stress Research Institute, Stockholm University.
    Performance prediction by sleepiness-related subjective symptoms during 26-hour sleep deprivation2008In: Sleep and Biological Rhythms, ISSN 1446-9235, E-ISSN 1479-8425, Vol. 6, no 4, p. 234-241Article in journal (Refereed)
    Abstract [en]

    Sleepiness is a major cause of lower productivity and higher risk of accidents in various work situations. Developing sleepiness monitoring techniques is important to improve work efficiency and to reduce accident risk, so that people can take a rest/break in appropriate timing before an accident or a mistake occurs. The aims of the present study are (1) to explain subjective sleepiness using sleep-related symptoms, and (2) to examine which symptoms are useful to predict performance errors. Participants were healthy paid volunteers (six males, six females; mean +/- SD, 31.5 +/- 10.74 years). Participants took part in 26-h sleep deprivation. During sleep deprivation, they carried out several performance tasks every 3 h and an hourly rating of questionnaires to evaluate subjective symptoms including two types of Karolinska sleepiness scale (KSS). The present study confirmed that performance errors can be predicted by subjective symptoms. While mental fatigue was correlated to KSS scores linearly, eye-related subjective symptoms showed quadratic correlations to KSS. By taking into consideration this noteworthy relationship between subjective symptoms and sleepiness, more accurate introspection of sleepiness and performance errors prediction (detection) may be possible.

  • 5.
    Rönnlund, Michael
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology. Umeå University, Faculty of Social Sciences, Centre for Population Studies (CPS).
    Vestergren, Peter
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    Mäntylä, Timo
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nilsson, Lars-Göran
    Stockholm University and Stockholm Brain Institute, Sweden.
    Predictors of self-reported prospective and retrospective memory in a population-based sample of older adults2011In: The Journal of Genetic Psychology, ISSN 0022-1325, E-ISSN 1940-0896, Vol. 172, no 3, p. 266-284Article in journal (Refereed)
    Abstract [en]

    In this article, the authors examined predictors of self-reported everyday memory failures using the Prospective and Retrospective Questionnaire (PRMQ; Smith, Della Sala, Logie, &Maylor, 2000) in a population-based sample of older adults (age range = 60–90 years; N = 250). The results showed that a higher frequency of reported failures was associated with lower scores on the personality dimension of self-directedness as assessed by the Temperament and Character Inventory (TCI; Cloninger, Dragan, Svrakic,& Przybeck, 1993) and more depressive symptoms on the Center for Epidemiological Studies Depression Scale (CES-D; Radloff, 1977).However, PRMQscores showed no relationships with objective memory ability, as reflected by a series of retrospective memory measures and a measure of prospective memory. Neither were the PRMQ scales associated with general cognitive functioning as assessed by the Mini-Mental State Examination (MMSE; Folstein, Folstein, & McHugh, 1977). Taken together, the results indicate that within the older population, self-reported memory as assessed by the PRMQ may reflect moodstate and personality factors rather than individual differences in memory and cognitive ability.

  • 6.
    Rönnlund, Michael
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Vestergren, Peter
    Umeå University, Faculty of Science and Technology, Umeå Mathematics Education Research Centre (UMERC). Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Stenling, Andreas
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nilsson, Lars-Göran
    Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI). Aging Research Center, Karolinska Institutet, Sweden.
    Bergdahl, Maud
    Bergdahl, Jan
    Umeå University, Faculty of Social Sciences, Department of Psychology. Department of Clinical Dentistry, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway.
    Dimensionality of stress experiences: Factorial structure of the Perceived Stress Questionnaire (PSQ) in a population-based Swedish sample2015In: Scandinavian Journal of Psychology, ISSN 0036-5564, E-ISSN 1467-9450, Vol. 56, no 5, p. 592-598Article in journal (Refereed)
    Abstract [en]

    We investigated the factorial structure of the Perceived Stress Questionnaire (PSQ-recent; Levenstein, Prantera, Varvo et al., 1993) in a large (N = 1516; 35-95 years) population-based Swedish sample (Nilsson, Adolfsson, Backman et al., 2004; Nilsson, Backman, Erngrund et al., 1997). Exploratory principal components analysis (PCA) was conducted on a first, randomly drawn subsample (n = 506). Next, the model based on the PCA was tested in a second sample (n = 505). Finally, a third sample (n = 505) was used to cross-validate the model. Five components were extracted in the PCA (eigenvalue > 1) and labeled "Demands," "Worries/Tension," " Lack of joy," " Conflict," and " Fatigue," respectively. Twenty-one out of the 30 original PSQ items were retained in a confirmatory factor analysis (CFA) model that included the five (first-order) factors and, additionally, a general (second-order) stress factor, not considered in prior models. The model showed reasonable goodness of fit [chi(2)(184) = 511.2, p < 0.001; CFI = 0.904; RMSEA = 0.059; and SRMR = 0.063]. Multigroup confirmatory factor analyses supported the validity of the established model. The results are discussed in relation to prior investigations of the factorial structure of the PSQ.

  • 7.
    Vestergren, Peter
    Umeå University, Faculty of Social Sciences, Department of applied educational science, Departement of Educational Measurement.
    On the subjective–objective distinction for measures of memory and cognition: Theoretical and methodological issues in questionnaire development and validation2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis was to develop a questionnaire for cognitive functioning, which could possibly be used as a screening instrument for early signs of dementia in the future. The introduction discusses the often made distinction between subjective and objective measures. A background to the four articles is provided, focussing on findings of weak relationships between self-report- and laboratory measures of memory/cognition. Studies I and II provided results and conclusions that guided instrument development and validation in Studies III and IV. All studies were based on data from participants in the Betula Prospective Cohort Study. Study I investigated predictors of scores on an established self-report instrument for memory failures (PRMQ). Candidate predictors were memory performance on laboratory tests, age, depressive symptoms, and personality traits. There was no relation to age, and test performance did not predict self-reported memory, but depressive symptoms and personality did. Given the finding of a lack of a relation to age, and a bulk of research articles claiming that memory complaints are common in the elderly or increase with age, Study II used a global rating of problems with memory, and reports of perceived causes. In contrast to Study I, problems ratings were related to age, such that increasing age meant higher severity of problems. Furthermore, perceived causes of memory problems differed across age. The elderly reported aging while the young reported stress and multitasking as primary causes. With these results as a background, the purpose of Study III was to develop a new instrument (the Cognitive Dysfunction Questionnaire - CDQ) with the explicit aim that scores should be related to laboratory test performance. A global construct of cognitive functioning with an emphasis on memory systems was adopted, and an item pool was generated. Based on exploratory principal components analysis and correlations with criterion measures (laboratory test performance), twenty items in six domains were selected. Preliminary psychometric evidence showed that the CDQ was reliable, and related to age and objective measures, but not to depressive symptoms. In Study IV, twenty additional items were constructed, and the CDQ was responded to by participants in independent samples. Confirmatory factor analysis was used to test the factor structure derived from Study III, and refinement was undertaken by collapse of two domains and exclusion of items. The final factor structure was cross-validated. Competing models and measurement invariance across age and sex was tested. Psychometric properties were investigated for the final 20-item version.

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    On the subjective–objective distinction for measures of memory and cognition
  • 8.
    Vestergren, Peter
    Umeå University, Faculty of Social Sciences, Department of Educational Measurement.
    The pilot version of the Cognitive Impairment Questionnaire: development and psychometric properties2009Conference paper (Other academic)
    Abstract [en]

    Objectives The objectives of this study were to develop and conduct a preliminary evaluation of a questionnaire for cognitive functioning in the adult general population.

    Methods 370 subjects from the Betula Prospective Cohort Study answered a questionnaire containing a 90 item pool pertaining to everyday failures of memory and cognition. Item selection for the reduced questionnaire was guided by associations with age and previous measures of objective cognitive performance, depressive symptoms, and perceived stress.

    Results Principal components analysis was conducted and 20 items loading on six components were selected for the final questionnaire. The total scale was internally consistent (Cronbach’s alpha = 0.90), had moderate correlations with age, objective memory/cognitive performance, and low correlations with depressive symptoms and perceived stress suggesting construct validity.

    Conclusion The pilot version of the CIQ is promising as a self-rating screening tool for milder forms of cognitive impairment in the adult general population.

  • 9.
    Vestergren, Peter
    et al.
    FoUU-unit/Neurotec/Psychiatry, Karolinska institutet, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
    Broman, J-E
    Hetta, J
    FATIGUE, SLEEPINESS AND SLEEP PROPENSITY IN INSOMNIA – RELATION TO SLEEP QUALITY AND QUANTITY2004In: Abstracts of the ESRS, Prague 2004., Blackwell Science Ltd , 2004, Vol. 13, p. 1-832Conference paper (Refereed)
  • 10.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University, Sweden.
    Perceived causes of everyday memory problems in a population-based sample aged 39–992011In: Applied Cognitive Psychology, ISSN 0888-4080, E-ISSN 1099-0720, Vol. 25, no 4, p. 641-646Article in journal (Refereed)
    Abstract [en]

    There is usually a weak relation between memory complaints and laboratory memory performance, but few studies have investigated what people perceive as causes of their everyday memory problems. This study investigated prevalence, severity and perceived causes of memory problems in a population-based sample (N = 361, age-range 39–99). 30.2 per cent of the participants reported memory complaints (at least moderate memory problems). Higher age was associated with more severe memory problems, but the age-related differences were small. The most frequent perceived causes were age/ageing, stress and multitasking. Age/ageing as a cause was more frequent among older participants, and stress and multitasking were more frequent among middle-aged participants. The results suggest that everyday stress and level of engagement in multiple tasks or commitments, that place demands on cognitive resources, are important variables to consider when studying the relations between subjective everyday memory measures, age and memory performance in the laboratory.

  • 11.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Does testing enhance memory by influencing subsequent restudy?2012Conference paper (Refereed)
  • 12.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB). Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
    Testing alters brain activity during subsequent restudy: Evidence for test-potentiated encoding2014In: Trends in Neuroscience and Education, ISSN 2211-9493, Vol. 3, no 2, p. 69-80Article in journal (Refereed)
    Abstract [en]

    Mixed testing/studying lead to better memory retention compared to repeated study only. A potentiating influence of tests on encoding, particularly during restudy of non-retrieved items, may contribute to this effect. This study investigated whether and how testing affects brain activity during subsequent restudy of Swahili–Swedish word pairs after a cued-recall test. Item-events during fMRI were categorized according to history (tested/studied only) and recall outcome at prescan and postscan tests. Activity was higher for tested compared to studied-only items in anterior insula, orbital parts of inferior frontal gyrus and hippocampus, and lower in regions implicated in the default network, such as precuneus, supramarginal gyrus and the posterior middle cingulate. Findings are discussed in terms of top-down biasing of attention to tested items with concomitant deactivation of regions in the default network. Increased/focused attention to tested items during restudy may lead to test-potentiated encoding via deeper semantic processing and increased associative binding.

  • 13.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Test-potentiated encoding of paired associates as revealed by functional magnetic resonance imaging2013In: Journal of cognitive neuroscience, ISSN 0898-929X, E-ISSN 1530-8898, Vol. 25, no Suppl., p. S113-S114Article in journal (Other academic)
  • 14.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Test-potentiated encoding revealed by fMRI: Viewing an old phenomenon with new glasses2013Conference paper (Other academic)
  • 15.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Social Sciences, Department of applied educational science.
    Rönnlund, Michael
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University and Stockholm Brain Institute, Sweden.
    Development of the cognitive dysfunction questionnaire (CDQ) in a population based sample2011In: Scandinavian Journal of Psychology, ISSN 0036-5564, E-ISSN 1467-9450, Vol. 52, no 3, p. 218-228Article in journal (Refereed)
    Abstract [en]

    The study reports on the development of a questionnaire for assessment of adult cognitive dysfunction (CDQ). Participants in a population-based sample(65 ± 15 years, N = 370) responded to a 90-item pilot version covering multiple aspects of memory/cognition. Based on exploratory principal components analyses and correlations with criterion measures of cognitive functioning (MMSE, Block Design, semantic/episodic memory), 20 items loading on 6 components were selected for the final version of the questionnaire. Cronbach’s a for the total score was 0.90. There was evidence of construct validity as judged by correlations between CDQ scores, objective cognitive measures, and a subjective memory measure (PRMQ). Discriminant validity was demonstrated by a low and non-significant correlation with depressive symptoms. Further evidence of construct validity was provided by correlations with age and educational attainment. In conclusion, the CDQ is promising as a self-rating screening tool for cognitive dysfunction, and will be the subject of further development and validation.

  • 16.
    Vestergren, Peter
    et al.
    Umeå University, Faculty of Social Sciences, Department of applied educational science, Departement of Educational Measurement.
    Rönnlund, Michael
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nyberg, Lars
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University and Stockholm Brain Institute, Sweden.
    Multigroup confirmatory factor analysis of the cognitive dysfunction questionnaire: instrument refinement and measurement invariance across age and sex2012In: Scandinavian Journal of Psychology, ISSN 0036-5564, E-ISSN 1467-9450, Vol. 53, no 5, p. 390-400Article in journal (Refereed)
    Abstract [en]

    The study adopted CFA to investigate the factorial structure and reduce the number of items of the Cognitive Dysfunction Questionnaire (CDQ; Vestergren, Rönnlund, Nyberg, & Nilsson, 2011). The analyses were based on data for a total of 1115 participants from population based samples (mean age: 63.0 ± 14.5 years, range: 25 - 95) randomly split into a refinement (n = 569) and a cross-validation (n = 546) sample. Equivalence of the measurement and structural portions of the refined model was demonstrated across the refinement and cross-validation samples. Among competing models the best fitting and parsimonious model had a hierarchical factor structure with five first-order and one second-order general factor. The final version of the CDQ consisted of 20 items in five domains (Procedural actions, Semantic word knowledge, Face recognition, Temporal orientation and Spatial navigation). Internal consistency reliabilities were adequate for the total scale and for the subscales. Multigroup CFAs were performed and the results indicate measurement invariance across age and sex up to the scalar level. Finally, higher levels of cognitive dysfunction as reflected by CDQ scores were observed with advancing age and with deficits in general cognitive functioning as reflected by scores on the Mini-Mental State Examination. In conclusion, adoption of the final version of the CDQ appears to be a way of measuring cognitive dysfunction without administering formal cognitive tests. Future studies should apply it among clinical groups to further test its usefulness.

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    Multigroup Confirmatory Factor Analysis
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