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Background Shift work can disturb circadian homeostasis and result in fatigue, excessive sleepiness, and reduced quality of life. Light therapy has been shown to impart positive effects in night shift workers. We sought to determine whether or not prolonged exposure to bright light during a night shift reduces sleepiness and enhances psychomotor performance among ICU nurses. Methods This is a single-center randomized, crossover clinical trial at a surgical trauma ICU. ICU nurses working a night shift were exposed to a 10-h period of high illuminance (1500–2000 lx) white light compared to standard ambient fluorescent lighting of the hospital. They then completed the Stanford Sleepiness Scale and the Psychomotor Vigilance Test. The primary and secondary endpoints were analyzed using the paired t test. A p  value <0.05 was considered significant. Results A total of 43 matched pairs completed both lighting exposures and were analyzed. When exposed to high illuminance lighting subjects experienced reduced sleepiness scores on the Stanford Sleepiness Scale than when exposed to standard hospital lighting: mean (sem) 2.6 (0.2) vs. 3.0 (0.2), p  = 0.03. However, they committed more psychomotor errors: 2.3 (0.2) vs. 1.7 (0.2), p  = 0.03. Conclusions A bright lighting environment for ICU nurses working the night shift reduces sleepiness but increases the number of psychomotor errors. Trial registration ClinicalTrials.gov, NCT03331822 . Retrospectively registered on 6 November 2017.

Night shift work can associate with an increased risk for depression. As night workers experience a ‘misalignment’ between their circadian system and daily sleep–wake behaviors, with negative health consequences, we investigated whether exposure to circadian misalignment underpins mood vulnerability in simulated shift work. We performed randomized within-subject crossover laboratory studies in non-shift workers and shift workers. Simulated night shifts were used to induce a misalignment between the endogenous circadian pacemaker and sleep/wake cycles (circadian misalignment), while environmental conditions and food intake were controlled. Circadian misalignment adversely impacted emotional state, such that mood and well-being levels were significantly decreased throughout 4 days of continuous exposure to circadian misalignment in non-shift workers, as compared to when they were under circadian alignment (interaction of “circadian alignment condition” vs. “day”, mood: p  < 0.001; well-being: p  < 0.001; adjusted p -values). Similarly, in shift workers, mood and well-being levels were significantly reduced throughout days of misalignment, as compared to circadian alignment (interaction of “circadian alignment condition” vs. “day”, mood: p  = 0.002; well-being: p  = 0.002; adjusted p -values). 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.

Background: Shift‐work schedules can cause sleep and psychological problems among nurses, negatively affecting their health and quality of life. This trial examined the effects of low‐energy light therapy on sleep, psychological symptoms, and heart rate variability among shift‐work nurses. Methods: This randomized controlled trial was conducted from July 2021 to June 2022. The inclusion criteria were nurses with self‐reported insomnia who worked in shifts in the last 6 months in a medical center in northern Taiwan. Block randomization was used to assign the study participants to two groups: experimental ( n = 32) and control ( n = 32). A portable Meridian Aura Cap equipped with a low‐level light‐emitting diode was used to provide red and near‐infrared light (660 and 850 nm) for 30 min, three times a week for 4 weeks; the control group did not receive any intervention. The Depression Anxiety Stress Scale‐21 and Insomnia Severity Index were used to measure psychological symptoms and sleep problems, respectively. Heart rate variability was measured by the ANSWatch. Results: No significant differences were reported in preintervention scores. After the 4‐week intervention, the intervention group scored significantly lower in insomnia (4.3 vs. 12.6, respectively; p < 0.001), depression (2.5 vs. 7.9, p < 0.001), anxiety (3.1 vs. 9.2, p < 0.001), and stress (5.6 vs. 12, p < 0.001) than those in the controls. No significant differences were observed in heart rate variability between the two groups. Conclusion: Low‐level light‐emitting diode light therapy improved sleep quality in shift‐work nurses with insomnia and alleviated depression, anxiety, and stress symptoms; however, it did not improve heart rate variability, possibly because of the short intervention duration and the ongoing shift‐work schedule. Implications for Nursing Management: Employers could consider providing phototherapy for shift nurses to improve their health. Trial Registration: ClinicalTrials.gov identifier: NCT05146596

Objectives This discussion paper aims to provide scientifically based recommendations on night shift schedules, including consecutive shifts, shift intervals and duration of shifts, which may reduce health and safety risks. Short-term physiological effects in terms of circadian disruption, inadequate sleep duration and quality, and fatigue were considered as possible links between night shift work and selected health and safety risks, namely, cancer, cardio-metabolic disease, injuries, and pregnancy-related outcomes. Method In early 2020, 15 experienced shift work researchers participated in a workshop where they identified relevant scientific literature within their main research area. Results Knowledge gaps and possible recommendations were discussed based on the current evidence. The consensus was that schedules which reduce circadian disruption may reduce cancer risk, particularly for breast cancer, and schedules that optimize sleep and reduce fatigue may reduce the occurrence of injuries. This is generally achieved with fewer consecutive night shifts, sufficient shift intervals, and shorter night shift duration. Conclusions Based on the limited, existing literature, we recommend that in order to reduce the risk of injuries and possibly breast cancer, night shift schedules have: (i) ≤3 consecutive night shifts; (ii) shift intervals of ≥11 hours; and (iii) ≤9 hours shift duration. In special cases - eg, oil rigs and other isolated workplaces with better possibilities to adapt to daytime sleep - additional or other recommendations may apply. Finally, to reduce risk of miscarriage, pregnant women should not work more than one night shift in a week.

Effective countermeasures against the adverse cardiovascular effects of circadian misalignment, such as effects experienced due to night work or jet lag, remain to be established in humans. Here, we aim to test whether eating only during daytime can mitigate such adverse effects vs. eating during the night and day (typical for night shift workers) under simulated night work (secondary analysis of NCT02291952). This single-blind, parallel-arm trial randomized 20 healthy participants (non-shift workers) to simulated night work with meals consumed during night and day (Nighttime Meal Control Group) or only during daytime (Daytime Meal Intervention Group). The primary outcomes were pNN50 (percentage consecutive heartbeat intervals >50 ms), RMSSD (root mean square of successive heartbeat differences), and LF/HF (low/high cardiac frequency). The secondary outcome was blood concentrations of prothrombotic factor plasminogen activator inhibitor-1 (PAI-1). These measures were assessed under Constant Routine conditions, before (baseline) and after (postmisalignment) simulated night work. The meal timing intervention significantly modified the impact of simulated night work on cardiac vagal modulation and PAI-1 ( p FDR = 0.001). In the Control Group, the postmisalignment Constant Routine showed a decrease in p NN50 by 25.7% ( p FDR = 0.008) and RMMSD by 14.3% ( p FDR = 0.02), and an increase in LF/HF by 5.5% ( p FDR = 0.04) and PAI-1 by 23.9% ( p FDR = 0.04), vs. the baseline Constant Routine. In the Intervention Group, there were no significant changes in these outcomes. For exploratory outcomes, the intervention significantly modified the impact of simulated night work on blood pressure ( P < 0.05), with no significant change in the Control Group, and a significant reduction by 6-8% ( P < 0.01) in the Intervention Group; without significant effects for heart rate or cortisol. These findings indicate that daytime eating, despite mistimed sleep, may mitigate changes in cardiovascular risk factors and offer translational evidence for developing a behavioral strategy to help minimize the adverse changes in cardiovascular risk factors in individuals exposed to circadian misalignment, such as shift workers. Circadian misalignment, which typically occurs in shift work, associates with cardiovascular diseases. Here the authors report that eating only in the daytime during simulated night work mitigates adverse changes in cardiovascular risk factors (including autonomic cardiac control, prothrombotic factor, and blood pressure) in a secondary analysis of a randomized controlled trial.

ObjectivesA decreased ability to repair oxidative DNA damage, due to melatonin suppression, is a compelling mechanism by which night shift workers are at an increased risk of cancer. We sought to determine if melatonin supplementation would improve oxidative DNA damage repair among night shift workers.MethodsWe conducted a parallel-arm randomised placebo-controlled trial of melatonin supplementation among 40 night shift workers. Supplements were consumed before engaging in day sleep over a 4-week period. All urine excreted during a representative day sleep and night work period before and during the intervention period was collected for measurement of creatinine-adjusted 8-hydroxy-2′-deoxyguanosine (8-OH-dG) as an indicator of oxidative DNA damage repair capacity, with higher concentrations indicating better repair. Linear regression models were used to analyse the association between ln-transformed 8-OH-dG concentration and intervention status during day sleep and night work.ResultsThe melatonin intervention was associated with a borderline statistically significant 1.8-fold increase in urinary 8-OH-dG excretion during day sleep (95% CI 1.0, 3.2, p=0.06). No statistically significant difference in 8-OH-dG excretion was observed during the subsequent night shift (melatonin vs placebo excretion ratio=0.9; 95% CI 0.6, 1.5; p=0.7).ConclusionsOur results suggest that melatonin supplementation improves oxidative DNA damage repair capacity among night shift workers. Future larger-scale trials are needed to evaluate the impact of varying doses of melatonin supplements and examine the impacts of longer-term use of melatonin supplements by night shift workers.

ObjectiveObservational studies indicate an association between working nights and miscarriage, but inaccurate exposure assessment precludes causal inference. Using payroll data with exact and prospective measurement of night work, the objective was to investigate whether working night shifts during pregnancy increases the risk of miscarriage.MethodsA cohort of 22 744 pregnant women was identified by linking the Danish Working Hour Database (DWHD), which holds payroll data on all Danish public hospital employees, with Danish national registers on births and admissions to hospitals (miscarriage). The risk of miscarriage during pregnancy weeks 4–22 according to measures of night work was analysed using Cox regression with time-varying exposure adjusted for a fixed set of potential confounders.ResultsIn total 377 896 pregnancy weeks (average 19.7) were available for follow-up. Women who had two or more night shifts the previous week had an increased risk of miscarriage after pregnancy week 8 (HR 1.32 (95% CI 1.07 to 1.62) compared with women, who did not work night shifts. The cumulated number of night shifts during pregnancy weeks 3–21 increased the risk of miscarriages in a dose-dependent pattern.ConclusionsThe study corroborates earlier findings that night work during pregnancy may confer an increased risk of miscarriage and indicates a lowest observed threshold level of two night shifts per week.

Night shift work has been suspected to increase breast cancer risk but epidemiological studies have been inconsistent due to heterogeneous assessment of exposure to night work. To overcome this limitation, we pooled data of five population-based case-control studies from Australia, Canada, France, Germany, and Spain into a single harmonized dataset using a common definition of night work including 6093 breast cancer cases and 6933 population controls. The odds ratio for breast cancer in women who ever worked at night for at least 3 h between midnight and 5 a.m. as compared to never night workers was 1.12 (95% CI 1.00-1.25). Among pre-menopausal women, this odds ratio was 1.26 [1.06-1.51], increasing to 1.36 [1.07-1.74] for night shifts ≥ 10 h, 1.80 [1.20-2.71] for work ≥ 3 nights/week, and 2.55 [1.03-6.30] for both duration of night work ≥ 10 years and exposure intensity ≥ 3 nights/week. Breast cancer risk in pre-menopausal women was higher in current or recent night workers (OR = 1.41 [1.06-1.88]) than in those who had stopped night work more than 2 years ago. Breast cancer in post-menopausal women was not associated with night work whatever the exposure metric. The increase in risk was restricted to ER+ tumors, particularly those who were both ER+ and HER2+ . These results support the hypothesis that night shift work increases the risk of breast cancer in pre-menopausal women, particularly those with high intensity and long duration of exposure. Risk difference between pre- and post-menopausal women deserves further scrutiny.

OBJECTIVE: Shift work is common across most societies but poses significant risks to the health of shift workers. In part, this risk is due to the disruption of healthy sleep-wake schedules. This systematic review identified qualitative research on shift workers’ experiences of sleep disturbance, fatigue and healthy behaviors. METHODS: We conducted a systematic search of four databases (CINAHL, EMBASE, MEDLINE, PsycINFO) and identified 28 eligible studies involving 1519 participants. We appraised the studies using an adapted Critical Appraisal Skills Programme (CASP) checklist, and confidence in the review findings was formally assessed using the Grading of Recommendations Assessment, Development and Evaluation-Confidence in the Evidence from Reviews of Qualitative research (GRADE‐CERQual) approach. Data were thematically synthesized. RESULTS: Three analytical themes were generated. ‘Inevitability of fatigue and tiredness’ outlines how shift workers experience a culture where they feel “peer pressure to soldier through” their shifts regardless of fatigue. ‘Balancing sleep needs with competing responsibilities’ highlights how shift workers struggle to balance the need for daytime sleep with family, leisure, and work responsibilities, often prioritizing family needs over their own sleep. ‘Obstacles to engaging in healthy behaviors’ describes how shift workers often know which actions would benefit their health and reduce fatigue but find it challenging to translate this knowledge into behavior due to fatiguing and stressful work environments. For the purposes of the GRADE-CERQual assessment, short summary statements were developed to describe 22 review findings: there was moderate or high confidence in all but one of these findings. CONCLUSION: This review suggests that sleep education alone is unlikely to be effective. Interventions should focus on helping shift workers self-regulate their behaviors, thoughts, and emotions to better manage sleep and fatigue.

To explore the evidence on nurses' experiences and preferences around shift patterns in the international literature. Electronic databases (CINHAL, MEDLINE and Scopus) were searched to identify primary studies up to April 2021. Papers reporting qualitative or quantitative studies exploring the subjective experience and/or preferences of nurses around shift patterns were considered, with no restrictions on methods, date or setting. Key study features were extracted including setting, design and results. Findings were organised thematically by key features of shift work. 30 relevant papers were published between 1993 and 2021. They contained mostly qualitative studies where nurses reflected on their experience and preferences around shift patterns. The studies reported on three major aspects of shift work: shift work per se (i.e. the mere fact of working shift), shift length, and time of shift. Across all three aspects of shift work, nurses strive to deliver high quality of care despite facing intense working conditions, experiencing physical and mental fatigue or exhaustion. Preference for or adaptation to a specific shift pattern is facilitated when nurses are consulted before its implementation or have a certain autonomy to self-roster. Days off work tend to mitigate the adverse effects of working (short, long, early or night) shifts. How shift work and patterns impact on experiences and preferences seems to also vary according to nurses' personal characteristics and circumstances (e.g. age, caring responsibilities, years of experience). Shift patterns are often organised in ways that are detrimental to nurses' health and wellbeing, their job performance, and the patient care they provide. Further research should explore the extent to which nurses' preferences are considered when choosing or being imposed shift work patterns. Research should also strive to better describe and address the constraints nurses face when it comes to choice around shift patterns.