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  • SAGE Publications  (8)
  • Biodiversity Research  (8)
  • 1
    Online Resource
    Online Resource
    SAGE Publications ; 2013
    In:  Journal of Biological Rhythms Vol. 28, No. 2 ( 2013-04), p. 130-140
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 28, No. 2 ( 2013-04), p. 130-140
    Abstract: Sleep is systematically modulated by chronotype in day-workers. Therefore, investigations into how shift-work affects sleep, health, and cognition may provide more reliable insights if they consider individual circadian time (chronotype). The Munich ChronoType Questionnaire (MCTQ) is a useful tool for determining chronotype. It assesses chronotype based on sleep behavior, specifically on the local time of mid-sleep on free days corrected for sleep debt accumulated over the workweek (MSF sc ). Because the original MCTQ addresses people working standard hours, we developed an extended version that accommodates shift-work (MCTQ Shift ). We first present the validation of this new version with daily sleep logs ( n = 52) and actimetry ( n = 27). Next, we evaluated 371 MCTQ Shift entries of shift-workers (rotating through 8-h shifts starting at 0600 h, 1400 h, and 2200 h). Our results support experimental findings showing that sleep is difficult to initiate and to maintain under the constraints of shift-work. Sleep times are remarkably stable on free days (on average between midnight and 0900 h), so that chronotype of shift-workers can be assessed by means of MSF—similar to that of day-workers. Sleep times on free-days are, however, slightly influenced by the preceding shift (displacements 〈 1 h), which are smallest after evening shifts. We therefore chose this shift-specific mid-sleep time (MSF E ) to assess chronotype in shift-workers. The distribution of MSF E in our sample is identical to that of MSF in day-workers. We propose conversion algorithms for chronotyping shift-workers whose schedules do not include free days after evening shifts.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2013
    detail.hit.zdb_id: 2018064-0
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    SAGE Publications ; 2019
    In:  Journal of Biological Rhythms Vol. 34, No. 6 ( 2019-12), p. 573-575
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 34, No. 6 ( 2019-12), p. 573-575
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2019
    detail.hit.zdb_id: 2018064-0
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    SAGE Publications ; 2019
    In:  Journal of Biological Rhythms Vol. 34, No. 6 ( 2019-12), p. 571-572
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 34, No. 6 ( 2019-12), p. 571-572
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2019
    detail.hit.zdb_id: 2018064-0
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    SAGE Publications ; 2020
    In:  Journal of Biological Rhythms Vol. 35, No. 4 ( 2020-08), p. 391-404
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 35, No. 4 ( 2020-08), p. 391-404
    Abstract: During adolescence, biological, psychosocial, and contextual factors converge in a “perfect storm” and have been put forward to explain the delay in chronotype observed at this age and the prevalence of disrupted sleep. This study provides evidence to support that chronotype and sleep patterns (particularly sleep duration) are socially constrained and to identify novel significant social predictors. Uruguayan public school activities are arranged in up to 4 shifts, creating a natural experiment to examine the effect of school timing on questionnaire-based assessments of sleep and chronotype. In this study, 268 high school students (15-18 years old) who attended school either on morning (0730 to 1130 h) or afternoon shifts (1130 h to 1530 h) responded to an adapted School Sleep Habits Survey. Students attending afternoon shifts had later chronotypes (a 1.5-h later midpoint of sleep on free days adjusted for sleep debt) than those attending the morning shift. Besides shift, evening social activities (including dinner time) were further identified as key predictors of late chronotypes, whereas age and gender were not. Sleep on school days was overall advanced and reduced with respect to weekends, and these effects were stronger in morning-shift students. Weekend sleep duration was similar between shifts, which probably caused the prevalence of reduced sleep durations (average weekly sleep duration, SDweek 〈 8 h) to be higher in morning-shift students (almost 80%) than in afternoon-shift ones (34%). Reduced sleep duration was significantly higher in morning-shift students. In addition, age, chronotype, and dinner time became relevant determinants of sleep deficit only in the morning-shift students. Besides the important social constraint of early school start time, this is the first study to confirm the significance of other types of social pressures on both adolescents’ chronotype and sleep deficit, which can be useful as potential new targets for effective policies to protect adolescent sleep.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2018064-0
    SSG: 12
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    SAGE Publications ; 2021
    In:  Journal of Biological Rhythms Vol. 36, No. 4 ( 2021-08), p. 395-409
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 36, No. 4 ( 2021-08), p. 395-409
    Abstract: The study aimed to explore chronotype-specific effects of two versus four consecutive morning or night shifts on sleep-wake behavior. Sleep debt and social jetlag (a behavioral proxy of circadian misalignment) were estimated from sleep diary data collected for 5 weeks in a within-subject field study of 30 rotating night shift workers (29.9 ± 7.3 years, 60% female). Mixed models were used to examine whether effects of shift sequence length on sleep are dependent on chronotype, testing the interaction between sequence length (two vs. four) and chronotype (determined from sleep diaries). Analyses of two versus four morning shifts showed no significant interaction effects with chronotype. In contrast, increasing the number of night shifts from two to four increased sleep debt in early chronotypes, but decreased sleep debt in late types, with no change in intermediate ones. In early types, the higher sleep debt was due to accumulated sleep loss over four night shifts. In late types, sleep duration did not increase over the course of four night shifts, so that adaptation is unlikely to explain the observed lower sleep debt. Late types instead had increased sleep debt after two night shifts, which was carried over from two preceding morning shifts in this schedule. Including naps did not change the findings. Social jetlag was unaffected by the number of consecutive night shifts. Our results suggest that consecutive night shifts should be limited in early types. For other chronotypes, working four night shifts might be a beneficial alternative to working two morning and two night shifts. Studies should record shift sequences in rotating schedules.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2018064-0
    SSG: 12
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  • 6
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 35, No. 1 ( 2020-02), p. 98-110
    Abstract: Individuals vary in how their circadian system synchronizes with the cyclic environment (zeitgeber). Assessing these differences in “phase of entrainment”—often referred to as chronotype—is an important procedure in laboratory experiments and epidemiological studies but is also increasingly applied in circadian medicine, both in diagnosis and therapy. While biochemical measurements (e.g., dim-light melatonin onset [DLMO]) of internal time are still the gold standard, they are laborious, expensive, and mostly rely on special conditions (e.g., dim light). Chronotype estimation in the form of questionnaires is useful in approximating the timing of an individual’s circadian clock. They are simple, inexpensive, and location independent (e.g., administrable on- and offline) and can therefore be easily administered to many individuals. The Munich ChronoType Questionnaire (MCTQ) is an established instrument to assess chronotype by asking subjects about their sleep-wake-behavior. Here we present a shortened version of the MCTQ, the µMCTQ, for use in situations in which instrument length is critical, such as in large cohort studies. The µMCTQ contains only the core chronotype module of the standard MCTQ (stdMCTQ), which was shortened and adapted from 17 to 6 essential questions, allowing for a quick assessment of chronotype and other related parameters such as social jetlag and sleep duration. µMCTQ results correspond well to the ones collected by the stdMCTQ and are externally validated by actimetry and DLMO, assessed at home (no measure of compliance). Sleep onset, midpoint of sleep, and the µMCTQ-derived marker of chronotype showed slight deviations toward earlier times in the µMCTQ when compared with the stdMCTQ ( 〈 35 min). The µMCTQ assessment of chronotype showed good test-retest reliability and correlated significantly with phase markers from actimetry and melatonin (DLMO), especially with measurements taken on work-free days. Because of its brevity, the µMCTQ represents an ideal tool to estimate individual internal time in time-critical contexts, from large cohort studies to individualized medicine.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2018064-0
    SSG: 12
    Location Call Number Limitation Availability
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  • 7
    Online Resource
    Online Resource
    SAGE Publications ; 2016
    In:  Journal of Ethnobiology Vol. 36, No. 4 ( 2016-12), p. 820-841
    In: Journal of Ethnobiology, SAGE Publications, Vol. 36, No. 4 ( 2016-12), p. 820-841
    Type of Medium: Online Resource
    ISSN: 0278-0771 , 2162-4496
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2016
    detail.hit.zdb_id: 2365050-3
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  • 8
    Online Resource
    Online Resource
    SAGE Publications ; 2013
    In:  Journal of Biological Rhythms Vol. 28, No. 2 ( 2013-04), p. 141-151
    In: Journal of Biological Rhythms, SAGE Publications, Vol. 28, No. 2 ( 2013-04), p. 141-151
    Abstract: This study explores chronotype-dependent tolerance to the demands of working morning, evening, and night shifts in terms of social jet lag, sleep duration, and sleep disturbance. A total of 238 shift-workers were chronotyped with the Munich ChronoType Questionnaire for shift-workers (MCTQ Shift ), which collects information about shift-dependent sleep duration and sleep timing. Additionally, 94 shift-workers also completed those items of the Sleep Questionnaire from the Standard Shift-Work Index (SSI) that assess sleep disturbances. Although all participants worked morning, evening, and night shifts, subsamples differed in rotation direction and speed. Sleep duration, social jet lag, and sleep disturbance were all significantly modulated by the interaction of chronotype and shift (mixed-model ANOVAs). Earlier chronotypes showed shortened sleep duration during night shifts, high social jet lag, as well as higher levels of sleep disturbance. A similar pattern was observed for later chronotypes during early shifts. Age itself only influenced sleep duration and quality per se, without showing interactions with shifts. We found that workers slept longer in fast, rotating shift schedules. Since chronotype changes with age, investigations on sleep behavior and circadian misalignment in shift-workers have to consider chronotype to fully understand interindividual and intraindividual variability, especially in view of the current demographic changes. Given the impact of sleep on health, our results stress the importance of chronotype both in understanding the effects of shift-work on sleep and in devising solutions to reduce shift-work–related health problems.
    Type of Medium: Online Resource
    ISSN: 0748-7304 , 1552-4531
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2013
    detail.hit.zdb_id: 2018064-0
    SSG: 12
    Location Call Number Limitation Availability
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