Abstract: Sleep has strong links to the symptomology of fibromyalgia syndrome (FMS), a diffuse musculoskeletal pain disorder. Information about the involvement of the circadian clock is, however, sparse. In this study, 1548 individuals with FMS completed an online survey containing questions on demographics, stimulant consumption, sleep quality, well-being and subjective pain, chronotype (assessed by the Munich ChronoType Questionnaire, MCTQ), and FMS impact. Chronotype (expressed as the mid-sleep-point on free days, corrected for sleep deficit on workdays, MSFsc) significantly correlated with stress-ratings, so-called âmemory failures in everyday life,â fatigue, FMS impact, and depression but not with anxiety. When chronotypes were categorized into 3 groups (early, intermediate, late), significant group differences were found for sum scores of perceived stress, memory failures in everyday life, fatigue, FMS impact, and depression but not anxiety, with late chronotypes being more affected than early chronotypes. Sleepiness ratings were highest in early chronotypes. Challenges of sleep quality and subjective pain were significantly increased in both early and late chronotypes. The results show that according to their reports, late chronotypes are more affected by fibromyalgia.
Abstract: Was haben Taxifahrer, Piloten, Krankenschwestern, Stahlarbeiter und Polizisten gemeinsam? Sie alle arbeiten im Schichtdienst â Arbeitszeiten auÃerhalb der üblichen Kernzeit von 9 bis 17 Uhr gehören für sie zum Alltag. Und diese Gruppe von Berufstätigen wächst stetig. Daraus ergibt sich ein zunehmendes Problem: Denn ungeachtet aller wirtschaftlichen und Âgesellschaftlichen Vorteile, welche die SchichtÂarbeit zweifellos bietet, bedroht sie die Gesundheit der Betroffenen. So können Schichtarbeiter schlechter ein- und durchschlafen als der NormalbürÂger; sie leiden häufiger unter Verdauungsstörungen und Sodbrennen, und auch Magengeschwüre, Herz-Kreislauf-Erkrankungen sowie selbst ein erhöhtes Krebsrisiko können Folge ihrer besonderen Belastungen sein. Wenn wir die Nacht zum Tag machen, etwa weil wir beruflich dazu gezwungen sind, gerät ein wichtiger Mechanismus unseres Körpers aus dem Takt: die innere Uhr. In den letzten ÂJahren haben Wissenschaftler die FunktionsÂweise dieses biologischen Taktgebers immer weiter entschlüsselt und die körperlichen Auswirkungen von Schichtarbeit analysiert â¦
Abstract: Shift-work seriously affects the health and well-being of millions of people worldwide, and the number of shift workers is constantly rising (currently approximately 20% of the workforce). While some effects are acute, others lead to chronic syndromes that persist after retirement. Though health problems in shift workers are well established, we still do not properly understand the causal mechanisms underlying shift-work's effects on health. One reason may be the heterogeneity in shift-work research design and methodology, rendering comparison between studies difficult or even impossible. Shift-work also involves a multitude of interacting factors, and we do not yet fully understand many of these interactions. Interindividual differences between workers are central predictors for health. Among these, individual differences in internal time (chronotype) should play a key role in a worker's ability to adjust to shift-work. While the importance of chronotype is receiving increased attention in chronobiology, it is still being largely ignored by shift-work studies, particularly by those performed in the field. Shift-work research would greatly benefit from increased attention to circadian components in real-life shift-work situations.Here, we summarize the current state of shift-work research in an attempt to address the reasons as to why we still do not clearly understand the links between shift-work and health. The aim of shift-work research should ultimately be to improve health and well-being (including social issues) in shift workers by means of improved work schedules. Society as a whole would benefit from such improvements â the individual worker, the health system, and industry.
Abstract: In 2007, the IARC (WHO) has classified "shift-work that involves circadian disruption" as potentially carcinogenic. Ample evidence leaves no doubt that shift-work is detrimental for health, but the mechanisms behind this effect are not well understood. The hormone melatonin is often considered to be a causal link between night shift and tumor development. The underlying "light-at-night" (LAN) hypothesis is based on the following chain of arguments: melatonin is a hormone produced under the control of the circadian clock at night, and its synthesis can be suppressed by light; as an indolamine, it potentially acts as a scavenger of oxygen radicals, which in turn can damage DNA, which in turn can cause cancer. Although there is no experimental evidence that LAN is at the basis of increased cancer rates in shiftworkers, the scenario "light at night can cause cancer" influences research, medicine, the lighting industry and (via the media) also the general public, well beyond shiftwork. It is even suggested that baby-lights, TVs, computers, streetlights, moonlight, emergency lights, or any so-called "light pollution" by urban developments cause cancer via the mechanisms proposed by the LAN hypothesis. Our commentary addresses the growing concern surrounding light pollution. We revisit the arguments of the LAN theory and put them into perspective regarding circadian physiology, physical likelihood (e.g., what intensities reach the retina), and potential risks, specifically in non-shiftworkers.
Abstract: A quarter of the world's population is subjected to a 1 hr time change twice a year (daylight saving time, DST). This reflects a change in social clocks, not environmental ones (e.g., dawn). The impact of DST is poorly understood. Circadian clocks use daylight to synchronize (entrain) to the organism's environment. Entrainment is so exact that humans adjust to the east-west progression of dawn within a given time zone. In a large survey (n = 55,000), we show that the timing of sleep on free days follows the seasonal progression of dawn under standard time, but not under DST. In a second study, we analyzed the timing of sleep and activity for 8 weeks around each DST transition in 50 subjects who were chronotyped (analyzed for their individual phase of entrainment). Both parameters readily adjust to the release from DST in autumn but the timing of activity does not adjust to the DST imposition in spring, especially in late chronotypes. Our data indicate that the human circadian system does not adjust to DST and that its seasonal adaptation to the changing photoperiods is disrupted by the introduction of summer time. This disruption may extend to other aspects of seasonal biology in humans.
Abstract: Humans show large inter-individual differences in organising their behaviour within the 24-h day-this is most obvious in their preferred timing of sleep and wakefulness. Sleep and wake times show a near-Gaussian distribution in a given population, with extreme early types waking up when extreme late types fall asleep. This distribution is predominantly based on differences in an individuals' circadian clock. The relationship between the circadian system and different "chronotypes" is formally and genetically well established in experimental studies in organisms ranging from unicells to mammals. To investigate the epidemiology of the human circadian clock, we developed a simple questionnaire (Munich ChronoType Questionnaire, MCTQ) to assess chronotype. So far, more than 55,000 people have completed the MCTQ, which has been validated with respect to the Horne-Ãstberg morningness-eveningness questionnaire (MEQ), objective measures of activity and rest (sleep-logs and actimetry), and physiological parameters. As a result of this large survey, we established an algorithm which optimises chronotype assessment by incorporating the information on timing of sleep and wakefulness for both work and free days. The timing and duration of sleep are generally independent. However, when the two are analysed separately for work and free days, sleep duration strongly depends on chronotype. In addition, chronotype is both age- and sex-dependent.
