Shift workers ‘cannot all adapt to a night shift’: new research

  • Sleep quality and circadian rhythms in night workers were found to be worse than in day workers
  • A University of Warwick study has equipped hospital workers with wearable technology to monitor physical activity and body temperature day and night
  • Workers would still show these effects even if they had worked nights for years before, suggesting that they are not adapting over time

Newswise — Scientists from the University of Warwick, together with those from the University of Paris-Saclay, Inserm and Assistance Publique-Hôpitaux de Paris (France), have challenged the widespread belief that shift workers are adapting to night work, using data from wearable technologies.

By following groups of French hospital staff working day or night during their work and free time, the researchers not only showed that night work significantly disrupts both the quality of their sleep and their circadian rhythms, but also that workers can experience such disruptions even after years. night work.

Their findings, reported in a study in the Lancet Group’s journal eBioMedicine, are the most detailed analysis of sleep and circadian rhythm profiles of shift workers ever attempted, and the first to also monitor body temperature. This key circadian rhythm is driven by the brain pacemaker clock and coordinates peripheral clocks in all organs.

Research demonstrates the value of remote monitoring technology in identifying early warning signs of illness risks associated with night work, opening up opportunities for intervention to improve worker health.

The study compared 63 night workers, working three nights or more for 10 hours each per week, and 77 day workers alternating morning and afternoon shifts in the same university hospital (Hôpital Paul Brousse in Villejuif , near Paris). Both groups wore accelerometers with chest surface temperature sensors throughout the day and night for a full week, with data collected by the Université Paris-Saclay research team and the Inserm.

The accelerometer measured the intensity of the movements and allowed the researchers to estimate how long the participants slept, the regularity of their circadian rhythms and whether this sleep was disturbed by the movements. Chest surface temperature patterns gave an additional indication of the participants’ circadian rhythm, the internal clock that coordinates rest and activity phases, variation in core body temperature, and a range other bodily rhythms.

Analysis by statisticians at the University of Warwick of sleep interruptions and rhythmic variations in core body temperature showed that night shift workers had less than half the median sleep regularity and quality of their colleagues by day. 48% of night workers had a disturbed temperature circadian rhythm.

Using information from the questionnaires about participants’ chronotypes, they also found that the sleep center of those who worked night shifts did not correlate with their respective chronotype, i.e. their morning or night orientation. . This meant they weren’t sleeping in sync with their internal clocks.

Importantly, even workers who had worked night shifts for many years still exhibited these negative effects on circadian and sleep health. The longer they had worked nights for years, the more severe the circadian disruption, which contradicts widely held assumptions about adaptation to night work.

This helps explain why previous research has linked disrupted circadian rhythms to long-term health risks, including the development of cancers and cardiovascular disease, as well as metabolic and infectious diseases.

Professor Bärbel Finkenstädt from the Department of Statistics at the University of Warwick said: ‘There is always an assumption that if you work night shifts you will adapt at some point. But you don’t. We have seen that most workers compensate in terms of quantity of sleep, but not in terms of quality during working time.

Dr Julia Brettschneider from the University of Warwick’s Department of Statistics said: ‘I think there is a misunderstanding that night work is just an inconvenience, when it can be linked to many serious health risks. We cannot avoid shiftwork for many professions, such as healthcare workers, so we should reflect on what can be done in terms of real adjustments to improve the working conditions and hours of shiftworkers. A better understanding of the biological mechanisms makes it possible to find answers to this question.

“Together with our PhD student Yiyuan Zhang, we have developed a statistical analysis framework that enables the discovery of patterns and predictors in the complex datasets created by wearable technology.”

Professor Francis Lévi of the University of Paris-Saclay added: “Almost 20% of night workers could not even adjust their circadian rhythms during their free time, the severity of the impairment tending to increase with the number of years of night work. The remote monitoring technology and analysis methods we have in place now make it possible to objectively assess the circadian and sleep health of night shift workers in near real time, and design preventive measures for individual workers whenever than necessary.

Additionally, the team has the potential in future research to look at longer-term outcomes, such as particular diseases such as cancer that have been linked to disruption of the circadian clock.

  • ‘Digital circadian and sleep health in individual hospital shift workers: A cross sectional telemonitoring study’ is published in eBioMedicineDOI: 10.1016/j.ebiom.2022.104121 Link:


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