Should we ban quick returns in shift work? Investigating acute effects on recovery

<p dir="ltr"><b>Background</b><b>:</b> Shift work is associated with negative effects on both health and safety, with insufficient sleep and recovery as a proposed pathway. The adverse effects from working shifts likely depend on the design of the shift schedule. A better understanding of individual shift components can help disentangle the complex relationship between shift work and its outcomes. The focus of this doctoral thesis is on quick returns, defined as having less than 11 hours of rest between consecutive shifts. Quick returns have been linked to reduced sleep duration, increased fatigue and higher risks of short-term sick leave and accidents. However, less is known about their effects on sleep quality, cognitive functioning, and work performance, as well as potential benefits of working quick returns. Moreover, few well-controlled field studies combining subjective reports with objective measures have examined the acute effects of quick returns.</p><p dir="ltr"><b>Aims:</b> This doctoral project aimed to clarify the mechanisms through which quick returns influence recovery and fatigue related risks. Study I explored the perceived benefits, drawbacks, and self-rated tolerance for quick returns. Study II examined the acute effects on sleep, sleepiness and stress. Study III investigated the impact of quick returns on sleep, sleepiness and performance.</p><p dir="ltr"><b>Methods:</b> In Study I, 96 nurses and assistant nurses completed a questionnaire on their views of quick returns. In Study II, 90 nurses and assistant nurses wore actigraphy wristbands and provided diary data during one quick return (evening-day transition) and one control condition (day-day transition). Study III used a quasi-experimental design following 36 newly graduated nurses across two prescheduled shift conditions: one with a quick return (off work-evening- day-day) and one control (off work-day-day-day). The participants wore actigraphy wristbands during sleep, kept work and sleep diaries, and performed short cognitive tests throughout the day.</p><p dir="ltr"><b>Results:</b> In Study I, the self-rated tolerance varied, suggesting that some individuals may be more vulnerable to the adverse effects of quick returns than others. Most participants associated quick returns with insufficient sleep and increased daytime fatigue, which also interfered with leisure time. Some experienced an increased risk of performance errors and mistakes, while some reported that quick returns benefited work-home balance and reduced stress on day shifts, but even larger proportions did not share these views. Quick returns were also found to benefit continuity in work processes. In Study II, quick returns were found to reduce sleep duration by 1 hour compared to day-day transition, leading to increased sleepiness during and after work. Participants reported poorer subjective sleep quality and increased anxiety at bedtime, but worktime stress and objective measures of sleep fragmentation did not differ between conditions. In Study III, quick returns shortened sleep by 46 minutes (to about six hours) and increased fatigue, with possible lingering fatigue on the subsequent dayshift although this estimate was uncertain. Again, participants reported poorer subjective sleep quality, while objective sleep efficiency and sleep fragmentation were unaffected. Although participants reported poorer cognitive ability after quick returns, they did not perform worse on cognitive tests compared to day-day transitions.</p><p dir="ltr"><b>Conclusions:</b> Quick returns do not allow for sufficient recovery, resulting in increased daytime fatigue, that could possibly interfere with work performance and safety. However, the cognitive test data suggest that nurses may be able to compensate for fatigue and maintain performance on short tasks. Furthermore, quick returns may benefit continuity in work processes in some organisations. Individuals may vary in their tolerance for quick returns, indicating that what constitutes a "safe" number of quick returns may differ depending on the individual and context. There was also tentative evidence that shift workers may not be able to recover properly when multiple day shifts follow quick returns, but these findings must be validated in future research. In sum, the findings of this thesis indicate that quick returns are associated with insufficient recovery and increased fatigue, which may help explain previously reported associations with higher risks of sick leave and accidents, and that they therefore should be avoided.</p><h3>List of scientific papers</h3><p dir="ltr">I. <b>Öster, K.</b>, Tucker, P., Söderström, M., & Dahlgren, A. (2023). Pros and cons of quick returns-a cross-sectional survey among Swedish nurses and nurse assistants. Industrial Health, 61(5), 379-392. <a href="https://doi.org/10.2486/indhealth.2022-0033" target="_blank">https://doi.org/10.2486/indhealth.2022-0033</a></p><p dir="ltr">II. <b>Öster, K.</b>, Tucker, P., Söderström, M., & Dahlgren, A. (2024). Quick returns, sleep, sleepiness and stress - An intra-individual field study on objective sleep and diary data. Scandinavian Journal of Work, Environment & Health, 50(6), 466-474. <a href="https://doi.org/10.5271/sjweh.4175" target="_blank">https://doi.org/10.5271/sjweh.4175</a></p><p dir="ltr">III. <b>Öster, K.</b>, Söderström, M., Tucker, P., Axelsson, J., Kecklund, G., & Dahlgren, A. Quick returns: a quasi-experimental field study on the effects of sleep, fatigue and cognitive performance. [Submitted]</p>