Blackmores Institute

In Australia, approximately 15% of the population are shift workers. The healthcare industry is the second largest body of shift workers, many of whom will be front line workers. Research confirms the impact of shift work is associated with an increased risk of physical and mental health conditions, including anxiety and depression. Disrupted circadian phases have been associated with these mood effects; however, there are limited experimental studies on ‘circadian misalignment’ as a cause. Two recent pivotal studies show that the inversion of the sleep/wake cycle (circadian misalignment) is a biological contributor to mood vulnerability. Additionally, rotating shifts, aimed to reduce night shifts, still caused stress and fatigue in front line workers.<table> <tr><td> Key Points - Shift work is associated with increased risk of depression and anxiety - Night shift work inverts the sleep/wake cycle (circadian misalignment) ­ - Circadian alignment is sleeping 11 pm to 7 am - Circadian misalignment (sleeping 11 am to 7 pm) decreases mood and wellbeing levels - In field Australian paramedic research found night work resulted in higher levels of stress, fatigue, and sleepiness ­ - Night work in rotating shifts still increased stress, fatigue and sleepiness - Circadian misalignment research can inform shift work guidelines </td></tr> </table><h3>Simulated study in shift and non-shift workers </h3> A laboratory study, involving 14 non-shift workers and nine shift workers, assessed the subjective effects of simulated shift work. Participants underwent circadian alignment phases (sleeping 11 pm to 7 am) and circadian misalignment phases (sleeping 11 am to 7 pm) – an inversion of the sleep/wake cycle by 12 hours. Both groups had significantly decreased mood and wellbeing levels with continued exposure to circadian misalignment. In the non-shift workers this exposure was over four days. The researchers concluded, ‘Our findings indicate that circadian misalignment is an important biological component for mood vulnerability, and that individuals who engage in shift work are susceptible to its deleterious mood effects.’<h3>Shift work adversely affects Australian paramedics</h3>Taking these results into real life, researchers performed a field study to investigate the relationship between circadian misalignment, sleep, mental health and physical activity in Australian paramedics. Paramedics work in rotating shifts, combining night shifts with day shifts and days off, to reduce night work but also to maintain 24-hour services. By monitoring 15 paramedics over eight consecutive days, researchers confirmed that night work was significantly associated with higher levels of stress, fatigue and sleepiness, even with rotating shifts. The authors stated, ‘Such shift-related issues have a compounding negative impact on an already stressful occupation with high rates of physical and mental health issues.’ <h3>Research can inform shift work guidelines</h3>These studies help to establish circadian misalignment as an important factor in mood vulnerability and highlight the adverse effects of shift work. These outcomes can inform ‘simple, yet effective evidence-based sleep/circadian interventions (e.g. appropriate light exposure, sleep hygiene) to improve the quality of life—an essential requirement for optimal mood— of shift workers.’ Sources:Chellappa SL, et al.: Circadian misalignment increases mood vulnerability in simulated shift work. Sci Rep. 2020;10(1). DOI: <a href="https://dx.doi.org/10.1038/s41598-020-75245-9">10.1038/s41598-020-75245-9</a>Khan WAA, et al.: A field investigation of the relationship between rotating shifts, sleep, mental health and physical activity of Australian paramedics. Sci Rep. 2021;11(1). DOI: <a href="https://dx.doi.org/10.1038/s41598-020-79093-5">10.1038/s41598-020-79093-5</a>Institute for Safety, Compensation and Recovery Research. Research Summary 284: Shift work in healthcare. February 2021. Available from: <a href="https://research.iscrr.com.au/__data/assets/pdf_file/0003/2560773/284_TRAN_REP_Shift-Work-in-Healthcare_FINAL_150221.pdf">https://research.iscrr.com.au/__data/assets/pdf_file/0003/2560773/284_TRAN_REP_Shift-Work-in-Healthcare_FINAL_150221.pdf</a>Australian Bureau of Statistics. Working Arrangements. August 2020. Available from: <a href="https://www.abs.gov.au/statistics/labour/earnings-and-work-hours/working-arrangements/latest-release">https://www.abs.gov.au/statistics/labour/earnings-and-work-hours/working-arrangements/latest-release</a>

Recent research finds that ‘circadian misalignment’ increases the risk of mood vulnerability, stress and fatigue in shift workers. Important findings for front-line healthcare professionals and the compounding negative impact – particularly in the current health crisis - on already stressful occupations.

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