Aligning Work and Circadian Time in Shift Workers Improves Sleep and Reduces Circadian Disruption

Abstract

Sleep loss and circadian disruption-a state of misalignment between physiological functions and imposed sleep/wake behavior-supposedly play central roles in the etiology of shift work-related pathologies [1-4]. Circadian entrainment is, however, highly individual [5], resulting in different chronotypes [6, 7]. Chronotype in turn modulates the effects of working times: compared to late chronotypes, earlier ones sleep worse and shorter and show higher levels of circadian misalignment during night shifts, while late types experience more sleep and circadian disruption than early types when working morning shifts [8]. To promote sleep and reduce the mismatch between circadian and working time, we implemented a chronotype-adjusted (CTA) shift schedule in a factory. We abolished the most strenuous shifts for extreme chronotypes (i.e., mornings for late chronotypes, nights for early ones) and examined whether sleep duration and quality, social jetlag [9, 10], wellbeing, subjective stress perception, and satisfaction with leisure time improved in this schedule. Intermediate chronotypes (quartiles 2 and 3) served as a control group, still working morning (6:00-14:00), evening (14:00-22:00), and night (22:00-6:00) shifts, with two strenuous shifts (out of twelve per month) replaced by evening ones. We observed a significant increase of self-reported sleep duration and quality, along with increased wellbeing ratings on workdays among extreme chronotypes. The CTA schedule reduced overall social jetlag by 1 hr, did not alter stress levels, and increased satisfaction with leisure time (early types only). Chronotype-based schedules thus can reduce circadian disruption and improve sleep; potential long-term effects on health and economic indicators need to be elucidated in future studies.

Chronotype and environmental light exposure in a student population

“…The MCTQ consists of questions concerning sleep timings for both workdays and free days separately, work time and time spent outside. The MCTQ has been validated against actigraphic recordings (Vetter et al 2015) and melatonin rhythms (Kitamura et al 2014). The MCTQ is used to calculate the MSF as the mid-point between sleep onset and sleep end.…”

Health and Leisure of Workers of Day and Night Shifts

“…Anyway, shift work based on chronotype may reduce the disruption of the circadian cycle and improve sleep and the potential long-term effects on workers' health. 36 Also with respect to issues related to workers' health, the adoption of risk behaviors also showed differences according to work shift. Cigarette smoking, for example, was statistically different among shifts.…”

Circadian Biology: The Early Bird Catches the Morning Shift

“…Thus, it seems that discovering the key to unlock and defy the human body's natural drive for nocturnal sleep is the next 'holy grail' for chronobiologists. In this issue of Current Biology, Vetter and colleagues [1] use chronobiology indicators to propose a solution for scheduling these extreme shift schedules.…”

“…To answer this question, Vetter and colleagues [1] describe an intervention study in a factory where the researchers did just that. During a baseline period, an individual's chronotype and initial sleep duration/quality were determined during their usual fast-forward rotating schedule, in which all workers completed an equal number of morning, evening, and night shifts.…”

“…ABA activates PYR receptors, which inhibit the PP2C phosphatases, thereby transducing a signal through SnRK2 kinases to activate downstream processes ( Figure 1A). This pathway evolved in an ancestor of all extant land plants to regulate expression of genes conferring desiccation and drought tolerance [1,3]. Homologs of ABA signalling components are found in liverworts, mosses and lycophytes (the extant bryophytes) [4][5][6][7][8] and these components have been shown to confer drought tolerance in liverwort and moss gametophytes [3,[9][10][11][12].…”