Biological and practical considerations regarding circadian rhythm and mental health relationships among nurses working night shifts: a narrative review and recommendations

Chidiebere Emmanuel Okechukwu1, Mark D. Griffiths2, Mauro Giovanni Carta3,
Edwin Nwobodo4, Sheikh Mohammed Shariful Islam5, Malcolm Forbes6, Michael Berk6,
Marc N. Potenza7,8,9,10, Maciej Banach11, Ojiakor Amamihechineke Grace12, Nkoli Nwobodo13,
Giuseppe La Torre1

1Department of Public health and Infectious Diseases, Sapienza University of Rome, Italy; 2Department of Psychology, Nottingham Trent University, England; 3Department of Public Health, Clinical and Molecular Medicine, University of Cagliari, Italy; 4Department of Human Physiology, Nnamdi Azikiwe University, Nigeria; 5Institute for Physical Activity and Nutrition, Deakin University, Australia; 6The Institute for Mental and Physical Health and Clinical Translation, Deakin University, Australia;7Department of Psychiatry and Child Study Center, Yale University School of Medicine, USA; 8Connecticut Mental Health Center, USA; 9Connecticut Council on Problem Gambling, USA; 10Department of Neuroscience, Yale University, USA; 11Department of Hypertension, Medical University of Lodz, Poland; 12Department of Internal Medicine, University of Nigeria, Nigeria; 13Milken Institute School of Public Health, The George Washington University, USA.

Summary. Background. Sleep is a vital physiological process regulated by the circadian clock and homeostatic mechanisms. Shift work is necessary to ensure continuity of healthcare provision. Worldwide, nurses work night shifts on a rotational or permanent basis. Objective. To analyse the impact of circadian rhythm disruption due to night shift work on the mental wellbeing of nurses. Methods. The literature search was conducted using PubMed and Scopus electronic databases. Selection criteria include studies published in English between 1997 and 2021 that examined the impact of night-shift work on the mental health of nurses. Results. The searches generated a total of 22 records on the PubMed database, and 9 records on the Scopus database, and a total of 31 studies. 29 papers were identified after removal of duplicates. However, 29 articles were screened based on the review of titles and abstracts. 19 articles were identified for full-test review. Seven papers were included in this review. Conclusions. Disrupted circadian rhythms and poor sleep quality and quantity have been identified as two of the most significant elements in the long-term effects of night-shift work on nurses’ mental health. Strategies and policies to promote workplace health may reduce the occurrence of mental health disorders among night-shift nurses, whether the shifts are rotational or permanent. Nursing supervisors and hospital administrators should consider developing new guidelines to minimize the negative impact of night shift rotations on mental health and the quality of life among nurses.

Key words. Circadian, mood disorders, nursing staff, occupational health, quality of life, shift work schedule, sleep, sleep disorders.

Considerazioni biologiche e pratiche riguardanti il ritmo circadiano e le relazioni con la salute mentale tra gli infermieri che lavorano nei turni notturni: una rassegna narrativa e raccomandazioni.

Riassunto. Introduzione. Il sonno è un processo fisiologico vitale regolato dall’orologio circadiano e dai meccanismi omeostatici. Il lavoro a turni è necessario per garantire la continuità dell’assistenza sanitaria. In tutto il mondo, gli infermieri lavorano su turni notturni a rotazione o tempo indeterminato. Scopo. Analizzare l’impatto dell’interruzione del ritmo circadiano dovuto al lavoro notturno sul benessere mentale degli infermieri. Metodi. La ricerca bibliografica è stata condotta utilizzando i database elettronici PubMed e Scopus. I criteri di selezione includono studi pubblicati in inglese tra il 1997 e il 2021 che hanno esaminato l’impatto del lavoro notturno sulla salute mentale degli infermieri. Risultati. Le ricerche hanno generato un totale di 22 record nel database PubMed e 9 record nel database Scopus e un totale di 31 studi. Ventinove documenti sono stati identificati dopo la rimozione dei duplicati. Tuttavia, 29 articoli sono stati selezionati in base alla revisione dei titoli e degli abstract. Diciannove articoli sono stati identificati per la revisione completa del test. 7 articoli sono stati inclusi in questa recensione. Conclusioni. Ritmi circadiani alterati e scarsa qualità e quantità del sonno sono stati identificati come due degli elementi più significativi negli effetti a lungo termine del lavoro notturno sulla salute mentale degli infermieri. Strategie e politiche per promuovere la salute sul posto di lavoro possono ridurre l’insorgenza di disturbi di salute mentale tra gli infermieri del turno di notte, indipendentemente dal fatto che i turni siano a rotazione o permanenti. I supervisori infermieristici e gli amministratori ospedalieri dovrebbero considerare lo sviluppo di nuove linee guida per ridurre al minimo l’impatto negativo delle rotazioni del turno di notte sulla salute mentale e sulla qualità della vita tra gli infermieri.

Parole chiave. Circadiano, disturbi dell’umore, disturbi del sonno, personale infermieristico, qualità della vita, salute sul lavoro, sonno, turni di lavoro.

Introduction

Worldwide, many nurses work during the night on a rotational or permanent basis. To enhance nursing staff allocation, reduce nurses’ workload, improve job performance, and promote mental wellbeing among nurses in the coronavirus diseases 2019 era, shift patterns should be organized systematically, and workers should be assigned coherently1. Sleep is a vital physiological process largely controlled by the circadian clock in the suprachiasmatic nucleus of the anterior hypothalamus. Shift work may promote the desynchronization of circadian rhythms and increase the risk of cognitive impairment among night-shift nurses over the course of time2. Night shift intolerance may reflect individual differences in responsiveness to internal desynchronization. Difficulties may manifest in the form of adjustments in sleep-wake cycles, alterations in body temperature, and grip strength of both hands3. Many night-shift nurses show signs of sleep-wake dysregulation in sleep alterations, asthenia, use of and dependence on sedating medications, and mood disorders3. The internal desynchrony of circadian rhythms in night-shift workers may be driven by light-induced phase shifting of the circadian activity clock4.

Shift work sleep disorder (SWSD) is a circadian rhythm sleep disorder characterized by sleeplessness, wakefulness, and/or extreme sleepiness. SWSD causes significant distress among night-shift nurses because their working hours overlap with sleep time, resulting in difficulties initiating sleep and maintaining wakefulness, as well as decreased work efficiency5,6. One study found that nurses performing night work had an odds ratio of 1.48 for insomnia and 1.78 for chronic fatigue compared to nurses with no night work experience7. SWSD in nurses has been linked to the number of nights on duty, gaps of less than 11 hours between working shifts, minimal flexibility, anxiety, and insomnia8. Moreover, shift work is associated with risks of committing errors in the healthcare setting, such as needle-stick injuries, mistakes while attending to patients, reduced harmonization, and inattention during working hours9. Drowsy driving is often reported by nurses in the morning after night shifts10. Night-shift workers appear at an elevated risk of experiencing sleepiness-related motor vehicle accidents due to cognitive dysfunction related to circadian rhythm disruption11. The circadian clock may not synchronize with the immediate environment during circadian misalignment12. Circadian clock dysregulation and sleep disturbances are harmful to hippocampus-dependent memory and adversely influence recollection of acquired skills. Circadian disruption and diminished sleep quality both decrease cognitive functioning and performance among night-shift nurses13. The neurobehavioral performance of healthcare workers is usually reduced during night shifts, possibly reflecting sleep loss and circadian misalignment14,15. Italian night-shift nurses had poorer psychomotor performance during night duty compared to nurses working day shifts16. Adjusting light and dark using dark sunglasses, sleeping in the dark, and exposure to bright light during night-shifts might help in reorganizing the circadian clock to discreetly align with the night work and day-sleep schedule, consequently decreasing circadian misalignment17. The combination of periodic bright light exposure and the use of darker sunglasses during and after the night shifts, respectively, may also promote better circadian adaptation18. Based on the above-mentioned literature, the objective of this review was to analyse the impact of circadian rhythm disruption due to night shift work on the mental wellbeing of nurses.

Methods

The selection criteria include studies published in English between 1997 and 2021 that examined the impact of night-shift work on the mental health of nurses. Non-English articles were excluded to avoid linguistic bias in translation. The searches were carried out using PubMed and Scopus electronic databases for studies published between 1997 and 2021. The following medical subject headings were used to search for relevant articles on the PubMed database: ((((Circadian Rhythm) OR Circadian Disruption) AND Nurses AND Night Shift-work AND Sleep AND Mental Health)). A total of 22 articles were found on PubMed. On the other hand, the following search terms were used to search for relevant studies on the Scopus database: ((((Night Shift-work) OR Circadian Disruption) AND Nurses AND Sleep AND Mental Health)). A total of 9 studies were found in Scopus. The search procedures are described in figure 1.




Inclusion criteria

This review included randomized controlled trials and intervention studies which conducted primary investigations into nurses working night shifts and were published in English between 1997 and 2021.

Exclusion criteria

Case studies, narrative reviews, systematic reviews, meta-analyses, literature reviews, and opinion articles were not included in the study. Papers that did not examine the impact of night-shift work on nurses’ mental health were also excluded.

Search outcomes

A total of thirty-one papers were found in the two databases (PubMed and Scopus), with two of them being duplicates. Seven papers were chosen for this review after a thorough evaluation of the 29 papers recorded after removal of duplicate publications based on the inclusion and exclusion criteria. Figure 1 shows the PRISMA flowchart for the selection.

Quality appraisal

The quality of the studies was evaluated using the study design-specific tool developed by the National Heart, Lung, and Blood Institute (NHLBI) and Research Triangle Institute International19. We gave point values (e.g., No= 0, Yes= 1, Good= 2, Fair= 1, Poor= 0) to each appraisal of quality and summed them for the final quality score, so that the higher the total score, the better the quality. Three authors reviewed the selected papers independently and unanimously approved the seven papers for the narrative review.

Synthesis and extraction

Six authors extracted data from the studies, which was later reviewed and discussed by all the authors. The data was synthesized via a descriptive approach, which involved a systematic description of a summary of the findings with tabulation of data (table 1)20-25.







The purpose of the descriptive synthesis was to categorize the findings and evaluate the effects of night-shift work on the mental health of nurses in various studies. The elements of mental health mostly evaluated in the studies are sleep quality, mood, and cognition.

Results

The searches generated a total of 22 records on the PubMed database, and 9 records on the Scopus database, and a total of 31 studies. 29 papers were identified after removal of duplicates. However, 29 articles were screened based on the review of titles and abstracts. 19 articles were identified for full-test review. 7 papers were eligible for inclusion in this review. The 7 studies were all selected for this narrative review based on their significance to the objectives of this study (figure 1). The selected studies were mostly cross-sectional studies (n=6), and one experimental study involving gene analysis (table 1).

The main findings of the selected papers

Clock gene polymorphisms may influence the adverse effects associated with circadian rhythm disruptions caused by working the night shift among nurses. Gamble et al.20, for example, analysed the role of chronotype on nurses’ ability to adjust to night shift work. They compared the effectiveness of typical sleep methods used by nurses on both working days and off days. They used single-locus and multi-locus techniques to analyse common polymorphisms of circadian/circadian-related genes in association with sleep/circadian phenotypes across diverse shift-work contexts in order to uncover gene-environment interactions. According to the findings of their study, night-shift nurses reported significantly lower adaptation to their work schedule than day-shift nurses, and analysis of three categories of adaptability revealed that night-shift nurses reported being significantly less well-adjusted to their work schedule than day-shift nurses20. Caffeine use was substantially associated with age; caffeine consumption did not significantly rise in day-shift nurses over the median age of thirty-six but increased significantly in night-shift nurses over the median age of thirty-six. According to the researchers, there may be a genetic risk for anxiety and mood disorders among night-shift nurses working in stressful settings, according to the analysis of gene-environment relationships. Genetic influences on behavior in night-shift nurses may have been demonstrated by disruption of the circadian system, as evidenced by the significant multi-locus model predicting the number of minutes to get out of bed20. Øyane et al.7 examined the effect of night work on anxiety, depression, insomnia, sleepiness, and fatigue among Norwegian nurses. They discovered that night-shift nurses are more likely than non-night-shift nurses to experience sleeplessness and chronic exhaustion. However, no significant associations were found between working night shifts and anxiety, depression, insomnia, sleepiness, and fatigue after multiple regression for nurses with at least 3 years of night work experience7. According to Ferri et al.21 nurses working rotational night shifts have lower job satisfaction compared to day-shift nurses. This was associated with physical and psychological symptoms related to stress, chronic fatigue, and poor sleep quality, which were more prevalent among night nurses compared to day-shift nurses21. According to Jensen et al.22, intensive care nurses working night shifts experienced significantly greater symptoms of mood swings and headaches than those working evening hours. In order to uncover individual factors associated with cognitive functioning during the night shift among hospital nurses working on irregular rotating-shift patterns, Zion & Shochat23 conducted a study on the impact of night-shift work on cognitive functioning among nurses working night shifts. They discovered that cognitive performance among hospital nurses drops throughout the middle of the night shift and rises towards the end of the shift; lower functioning is linked to increased subjective sleepiness, older age, and longer time awake.23 According to the findings of a study by Dai et al.24, 353 nurses (40.8%) among 865 day and night shift nurses had depressive symptoms. Nurses working night shifts were younger, had higher Pittsburgh Sleep Quality Index and Hospital Anxiety and Depressive Disorders Rating Scale scores, and worked longer hours than nurses working day shifts only. A positive correlation was also found between the Pittsburgh Sleep Quality Index and the Hospital Anxiety and Depressive Disorders Rating Scale, indicating that a greater incidence of depressive symptoms among nurses working night shifts may be linked to lower sleep quality caused by the night shift.24 According to Feng et al.25, night-shift nurses, had poorer sleep quality and more health issues compared to day-shift nurses. Compared to day-shift nurses, night shift nurses have a higher rate of poor subjective sleep quality, sleep latency, sleep efficiency, sleep disruption, and daytime dysfunction. Night-shift nurses may be more vulnerable to sleep disorders, difficulties falling asleep, taking a long time falling asleep, tiredness, and insomnia during the day, than day-shift nurses. The physical health of night shift nurses was worse than day shift nurses, but there was no difference in psychiatric issues between the two groups25.

Discussion

Working night shifts is associated with negative mental health consequences, such as depression24,25. According to Dai et al.24, Chinese nurses working night shifts were younger, had a lower job rank and marriage rate, and worked longer hours. Furthermore, marital status was linked to symptoms of depression. Nevertheless, the high points of their studies were that nurses who worked night shifts had more depressive symptoms than those who worked only day shifts; nurses who had poorer sleep quality had more depressive symptoms; and nurses who worked night shifts had poorer sleep quality than those who worked only day shifts24. According to Jensen et al., mental symptoms such as headaches and mood swings are common among nurses working the night shift22. When compared to day-shift nurses, night-shift nurses had a higher rate of poor sleep quality25. Cognitive performance was reduced among night-shift nurses, which was associated with lack of sleep and reduced alertness23. Night-shift work may slowly decrease nurses’ work performance and potentially increase their risk of medication errors (e.g., via inattention or mathematical errors), particularly towards the end of the shift21,23.

It is important to develop and test interventions to target circadian misalignment, excessive sleepiness, and insomnia among night-shift nurses. Attempts to resynchronize circadian rhythms may reduce depression and other issues associated with night-shift work26. Behavioral interventions should be developed and implemented to increase awareness of staying healthy while working as a nurse27. Yoga may be useful for relieving occupational stress among nurses working the night shift28. Night-shift nurses should endeavour to consume food at appropriate times and eat a healthy diet, such as a diet rich in fibre, polyphenols, and unsaturated fatty acids (Mediterranean diet). Adherence to the Mediterranean diet has been associated with better mental health29. Exogenous melatonin can be used to advance the sleep-wake rhythm30,31. Eszopiclone, zolpidem, and suvorexant may improve short-term sleep outcomes for adults with insomnia, but precautions should be taken when administering them32. Agomelatine, which acts by agonizing melatonergic M1/M2 receptors and antagonizing serotonergic 5-HT2c receptors, respectively, may be effective as a resynchronizing agent for resetting the central clock and reducing depressive and anxiety symptoms33. Adaptation to shift work can be improved using bright light therapy, and phase resetting is achieved because the individual’s light exposure patterns have been synchronised with the baseline circadian phase34. Ergonomic work schedules should be implemented by employers to preserve and protect the health of their employees and help minimise the psychological stress induced by working night-shifts35. Hospital administrators should develop and implement risk-management schemes to mitigate work-related fatigue among night-shift nurses and to improve patient safety36. Nursing supervisors should consider scheduling pauses/naps among night-shift nurses as a preventive strategy to attenuate the adverse effects of night-shift work37. D’Ettorre and Pellicani38 found that a fast-forward alternating ergonomic shift among healthcare workers was useful in preventing misalignment between sleep-wake rhythm and shift work. The approach was associated with reduced risk as assessed by the Rotating Shiftwork Questionnaire and reduced sleepiness as assessed by the Epworth Sleepiness Scale. They evaluated the alternating ergonomic shifts by preparing work schedules in three phases. The day before the night-shift, the nurses must have had unhindered sleep in the morning before the first shift, awoken without an alarm, and supplemented sleep periods by napping during the afternoon38. During night shifts, nurses should have kept shift naps to less than 30 minutes to avoid slow wave sleep and tiredness on waking, taken caffeine only once before napping, eaten satisfactorily to stay relaxed during the shift, and endeavoured to avoid caffeine and nicotine for several hours towards the end of the shift. After the night shift, nurses should have napped for 90 to 180 minutes immediately after getting home, gone outside after waking up, and gone to bed early38.

Nurse administrators should identify and implement novel approaches to improve mental wellbeing and sleep quality among nurses working night shifts. Enhancing sleep quality and mental wellbeing among night-shift nurses will improve their overall health, work efficiency and performance. Developing new ideas to improve the sleep patterns and quality among nurses working night shifts is vital in order to convince upcoming nurses to work night shifts. We classified known interventions into non-pharmacological/behavioral approaches, pharmacological approaches, and occupational/regulatory approaches (table 2)39-42.










Moreover, a combination of the afore-mentioned interventions may be more effective in improving sleep quality, vigilance and mental wellbeing among nurses working night shifts.

In humans and animal models, being active during the normal resting phase generates desynchrony in the hypothalamus, disrupting hormonal and neurobehavioral function43. Internal desynchrony has been linked to an increased risk of mental disorders among night-shift nurses44. Sleep deprivation is linked to poor cognitive performance (inattention and episodic memory)45. Circadian misalignment is associated with night-shift work, leading to sleepiness, drowsiness, and fatigue, not only among nurses but among the general healthcare workforce46. However, scheduled naps in the hospital setting appear to be an effective strategy to mitigate drowsiness and improve alertness among nurses during night duty47. Two to 3 hours of napping during the night shift increases the likelihood of recovery after work48.

Salivary cortisol levels have been found to be higher for night-shift nurses compared with day-shift neonatal intensive care unit nurses, suggesting that night-shift work is associated with higher levels of physiological stress49. The degree of fatigue is usually aggravated among nurses after night shifts50. Circadian disruption has been linked to the development of mood disorders51. Sleep disturbances and diurnal mood swings are common in depressed patients52. In one study, being at elevated risk of experiencing SWSD was the most significant statistical predictor of depression53. The pathophysiological mechanism underlying the link between circadian disruption and depression remains unknown54. Clock genes are thought to play a role in mood regulation55. Circadian genes such as CLOCK, ARNTL1, NPAS2, PER3 and NR1D1 have been linked to bipolar and depressive disorders56, implying that genetic, and environmental factors associated with internal desynchronization may be involved in the pathophysiology of mood disorders57. Behavioural sleep approaches are associated with nurses’ adaptation to a typical night-shift schedule58. Nurses are essential for the safety and well-being of patients. Therefore, the implementation of new sleep promotion strategies may reduce sleep/wake dysregulation among nurses and improve their overall wellbeing and job performance59.

Future perspectives

Night-shift work has adverse health consequences for nurses worldwide, and it can affect their job performance and compromise patient safety. Therefore, there is a need to design effective measures to mitigate the adverse health correlates of night-shift work on the wellbeing of nurses. Mathematical and machine learning models may be used to design night-shift work timetables using light exposure and sleep-wake data of workers to create personalised shift work schedules to improve circadian alignment, which may in turn increase sleep, alertness, and job performance60. Additional cutting-edge studies are required to develop novel strategies to promote sleep and wakefulness and to retrain the circadian clock to adjust to different work schedules among nurses working night shifts.

Recommendations for nursing management

Occupational health promotion strategies and policies may reduce the risk of mental health disorders among night-shift nurses, irrespective of whether they are permanent or rotating night-shift workers. Behavioral signs associated with circadian rhythm disruption could be tracked among nurses working night shifts, and real-time data can be assessed using wearable devices or smartphones with sensors and apps. Moreover, regular assessment of mental wellbeing and screening for sleep disorders among night-shift nurses may help identify individuals at elevated risk of unfavourable health and safety concerns at work, and further preventive and treatment strategies may be designed for them. Scheduled breaks for night-shift nurses to take naps during night duty may help reduce mental fatigue. Timed bright light therapy may be used to manage SWSD and related mental health concerns. Bright light therapy can reset the internal clock and gradually shift sleep patterns to normal. Nursing supervisors and hospital administrators should examine their present rotational shift methods and assess the effects on nurses’ mental states and quality of life. Similar considerations may apply to other professions working night shifts in the healthcare setting and other sectors.

Strengths and limitations

The strengths of this review were that it addressed the potential association between circadian disruption, poor sleep quality and the mental health of nurses, and mechanistic insight that may help in the design of new workplace sleep promotion interventions for nurses. The limitations of this review were that most included studies were cross-sectional, and some publications analysed mostly self-reported data.

Conclusions

Disrupted circadian rhythms and poor sleep quality and quantity have been identified as two of the most significant elements in the long-term effects of night-shift work on nurses’ mental health. Night-shift work is associated with psychological distress and impaired concentration among nurses and may contribute to the development of depressive and anxiety disorders. Night-shift work may also contribute to errors and poor performance in the workplace. Interventions to mitigate the potential adverse impact of night-shift work on mental wellbeing should aim to restore disrupted circadian rhythms or prevent further disruption of the physiologic clock by identifying and improving physical, psychosocial, behavioral, biological, and environmental factors contributing to performance among nurses during the night shift in every work setting.

Conflict of interests: the authors have no conflict of interests to declare.

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