Chronotype in relation to shift work: A cohort study among 37,731 female nurses.

Chronotype may affect tolerance for circadian disruption induced by shift work. This study examines the association between chronotype, self-reported sleep timing, shift type preference, and sleep problems among nurses, and studies chronotype stability over time. The study included 37,731 Dutch female nurses who completed a baseline (2011) and follow-up questionnaire (2017), with information on shift work (e.g., job history, shift type preference [collected in 2017 only]), and sleep characteristics (e.g., chronotype, preferred sleep-wake time in a work-free period [collected in 2017 only], and sleep problems between working days according to Medical Outcomes Study-Sleep Problem Index II [MOS-SPI-II]). The association between chronotype and sleep timing was examined using (age-adjusted) linear regression. Associations between chronotype and shift type preference and sleep problems (MOS-SPI-II >30) were examined using ordered logistic and Poisson regression, respectively. With later chronotype, midsleep time increased (definite evening vs. intermediate types [reference]: ß = 55 min, 95% confidence interval [95% CI]: 54-55), the odds ratio (OR) for 1-point increase in preference for night (2.68; 95% CI: 2.48-2.90) and evening shifts increased (OR 2.20; 95% CI: 2.03-2.38), while the odds for day (OR 0.17; 95% CI: 0.16-0.18) and morning shifts (OR 0.22; 95% CI: 0.21-0.24) decreased. Intermediate chronotype was associated with fewer sleep problems (median MOS-SPI-II = 27.2, p < 0.01), compared with definite morning (28.9) and evening types (31.7). This study shows that chronotype is associated with sleep-wake times in a work-free period, shift type preference, and sleep problems in nurses. Future studies on the association of shift work-induced circadian disruption and health outcomes should therefore consider chronotype as effect-modifier.

Independent and joint trajectories of depression and anxiety symptoms among Chinese male sailors throughout a prolonged non-24-h rotating shift schedule at sea: a parallel-process growth mixture modeling approach.

BACKGROUND: The predictive and protective effect of hardiness on mental health remains unclear among shift workers on non-24-h working schedules. The present study aimed to investigate the independent and joint trajectories of depression and anxiety symptoms and the role of hardiness during a prolonged period of non-24-h shift working schedule. METHODS: Four hundred nine Chinese male sailors (working on 18-h watchstanding schedule) were recruited and completed all 5-wave tests through online questionnaires (at Day 1, 14, 28, 42, 55, respectively) during a 55-day sailing. The questionnaires included sociodemographic variables, hardiness, depression and anxiety symptoms. Independent and joint trajectories of depression and anxiety symptoms were estimated by latent growth mixture models. The effect of hardiness on trajectories was examined by logistic regression models. RESULTS: 2 and 3 latent trajectories were identified for depression and anxiety symptoms, respectively. Based on initial levels and development trends, 3 distinct joint trajectories of depression and anxiety were identifed and named as: "Low-Inverted U" group (73.6%), "Moderate-Deterioration" group (6.9%), and "High-Stable" group (9.5%). Sailors with higher levels of hardiness were more likely to follow the "Low-Inverted U" trajectory of depression and anxiety symptoms (all p < 0.001). CONCLUSIONS: There existed individual differences in the trajectories of depression and anxiety. Hardiness may have a protective effect that can prevent and alleviate depression and anxiety symptoms. Therefore, hardiness-based intervention programs are encouraged among the shift workers on non-24-h working and rest schedules.

Hardiness, psychosocial factors and shift work tolerance among nurses - a 2-year follow-up study.

AIM: To examine the predictive power of the subfactors of hardiness (commitment, control and challenge) on shift work tolerance (measured with sleepiness, fatigue, anxiety and depression) over 2 years in nurses working shifts. We also investigated the direct effects of psychosocial variables such as role conflict, social support and fair leadership on shift work tolerance, as well as their moderating role on the relationship between hardiness and shift work tolerance. BACKGROUND: Several scholars have discussed the role of individual differences and psychosocial variables in predicting shift work tolerance. The conclusions are not clear. DESIGN: Longitudinal questionnaire study. METHODS: A sample of Norwegian nurses employed in shift work including nights participated in this longitudinal questionnaire study: 1877 at baseline, 1228 at 1-year follow-up and 659 nurses at 2-year follow-up. Data were collected in three waves, first wave in 2008 and third in 2011 and were analysed with a series of hierarchical multiple regression analyses. RESULTS: We found that the subfactor commitment could predict fatigue over 1 year and anxiety and depression over 2 years. Challenge could predict anxiety over 1 year. Control was unrelated to shift work intolerance. Hardiness did not predict sleepiness. Social support, role conflict and fair leadership were important for some aspects of shift work tolerance; however, hardiness seemed to be more eminent for shift work tolerance than the psychosocial variables. Social support moderated the relationship between hardiness and shift work tolerance to some degree, but this interaction was weak. CONCLUSION: Hardiness can to some degree predict shift work tolerance over 2 years among nurses.

Adaptive sleep behaviours and shift work tolerance during the transition to shift work.

OBJECTIVE: To evaluate whether recruit paramedics adapt their sleep behaviour during the first 12-months of shift work and to identify sleep behaviours that are associated with better shift work tolerance (SWT) after 12-months of shift work. METHODS: Recruit paramedics (n = 105; Mage = 25.81 years; 51.38% female) were evaluated before (baseline), and after six- and 12-months of shift work. At each timepoint, participants completed questionnaires evaluating their mental health and sleep. Participants also underwent 14 days of sleep and shift monitoring (sleep/work diaries and actigraphy) at each timepoint to examine sleep behaviours, including sleep opportunity (SO), sleep regularity and number of sleep episodes. RESULTS: Linear mixed models found SO increased (on day shifts and rest days), and sleep regularity decreased between baseline and follow-up timepoints. There were no changes in SO (on day shifts, nightshifts, and rest days) or sleep regularity between six- and 12-months of shift work. Latent profile analysis at 12-months follow-up identified high (n = 52), medium (n = 27), and low (n = 9) SWT levels (measured via depression, anxiety, insomnia, sleep quality and sleep efficiency) in paramedics. Reduced sleep regularity (i.e., more irregular sleep) between six- and 12-months of work and prioritising major sleep (rather than naps) at six-months predicted high SWT. CONCLUSIONS: These findings suggest clear SWT levels exist early in paramedics' careers whereby symptoms of depression, anxiety, and insomnia were the strongest contributors to SWT. New paramedics' sleep behaviours, including sleep regularity and prioritisation of longer sleep between nightshifts, may play an important role in influencing how paramedics tolerate shift work.

Sleep, mental health and physical health in new shift workers transitioning to shift work: Systematic review and meta-analysis.

This systematic review and meta-analysis (PROSPERO registration CRD42022309827) aimed to describe how shift work impacts new workers' sleep, mental health, and physical health during the transition to shift work and to consolidate information regarding predictors of shift work tolerance (SWT) during this transition period. Inclusion criteria included: new shift workers; sleep, mental health, or physical health outcomes; prospective study design with the first timepoint assessing workers within three months of starting shift work; and written in English. Searches from six databases returned 12,172 articles as of August 2023. The final sample included 48 papers. Publication quality and risk of bias was assessed using the critical appraisal skills program. Forty-five studies investigated longitudinal changes in sleep, mental health, or physical health outcomes and 29 studies investigated predictors of SWT (i.e., better sleep, mental and physical health). Sleep and mental health outcomes worsened following the onset of shift work, while physical health did not significantly change. Pre-shift work mental health, sleep, and work characteristics predicted SWT later in workers' careers. Shift work adversely impacts new workers' sleep and mental health early in their career, and interventions before beginning shift work are needed to promote better SWT.

A latent profile analysis of shift work tolerance among Chinese male sailors during a prolonged non-24-h rotating shift schedule at sea.

Shift work tolerance (SWT) refers to the ability to adapt to shift work without significant adverse consequences. The present study aimed to examine the individual differences in SWT and their predictors and outcomes. Latent profile analyses were conducted using cross-sectional data collected form 448 Chinese male sailors who experienced a prolonged (>30 d) non-24-h rotating shift schedule at sea. Depression, anxiety, sleep disturbance, fatigue, domestic disruption, job satisfaction, work engagement, digestive and cardiovascular symptoms were included as indicators of SWT. The results showed that there existed 2 latent profiles of SWT named as High SWT group and Low SWT group. High SWT group was characterized by low levels on all negative bio-psycho-social outcomes but high levels of work engagement and job satisfaction, while Low SWT group exhibited completely opposite characteristics compared to High SWT group. The level of hardiness could predict profile membership that those with higher level of hardiness were more likely to belong to High SWT group. However, there were no significant differences observed in job performance between two groups. In conclusion, hardiness can serve as a predictor of personnel selection for shift work and hardiness-based intervention programs should be encouraged among the shift workers.

Pros and cons of quick returns-a cross-sectional survey among Swedish nurses and nurse assistants.

Short rest (<11h) between evening and day shifts-known as quick returns (QRs)-impede recovery and may impair health. Nevertheless, QRs remain popular among some shift workers. This study explores nurses' and nurse assistants' perceptions of the merits and demerits of QRs from individual and organizational perspectives. Participants were recruited from eleven wards at two Swedish hospitals as part of a larger quasi-experimental intervention study. The majority (79%) had influence over their work schedules. Frequency distributions of responses are presented. Ninety six undertook a baseline survey regarding recovery, tolerance and work performance in relation to QRs. A majority experienced difficulties unwinding before bedtime (76%), insufficient sleep (80%), and daytime fatigue (72%). A third experienced an increased risk of errors and mistakes. However, QRs appeared to facilitate taking reports from patients and planning work, as this task was more often rated as 'very easy' following a QR compared to other shift combinations. Tolerance of QRs varied substantially. In conclusion, QRs seem to benefit continuity in work processes, but may do so at the expense of recovery and safety. Wards planning to reduce QRs-through participatory or fixed schedule models-should consider impacts on work processes.

Evaluation of the Diurnal Cycle of Blood Pressure and Sleep in Shift Workers.

BACKGROUND: Circadian misalignment of physiological factors in shift workers is poorly studied in the Indian population. In the present study, 24-hour blood pressure measurements were taken on the same subject twice, once during his morning and night shifts. Sleep was also monitored by a self-reported sleep diary, which was confirmed with an activity monitor, and the sleep quality was assessed using sleep questionnaires. OBJECTIVE: This study aimed to discover the pattern of blood pressure variation, the dipping and non-dipping status, and its correlation with sleep. METHODOLOGY: This observational study was conducted in the Department of Physiology, All India Institute of Medical Sciences (AIIMS), Rishikesh, from April 2019 to September 2019, among security guards working rotating shifts in the Rishikesh hospital premises. Participants were given an activity sheet with instructions to document their daily activities for a complete 24-hour period on the designated measurement day, including recording the time of waking up and going to sleep. A wrist-worn activity monitor was utilised to assess the self-reported sleep duration provided by each participant on the activity sheet. RESULTS: The present study showed the mean age of the participants as 27.03 ± 2.71 years, along with a mean body mass index (BMI) of 22.10 ± 1.64. Sleep duration was significantly higher during the morning shift (5.81 ± 1.08 hours) compared to the night shift (4.02 ± 1.70 hours) on the day of ambulatory blood pressure monitoring (ABPM) recording. The mean difference in systolic blood pressure between night shift workers between their awake and sleep periods was 15.91 ± 8.44 mmHg. However, no statistically significant disparity was seen when comparing the systolic blood pressure at the 24-hour mark during wakefulness and sleep between those working morning and night shifts (p >0.05). CONCLUSION: The current study's findings indicate that participation in shift work, particularly night shift work, could potentially play a role in the emergence of irregular circadian blood pressure patterns and potentially lead to a lack of nocturnal blood pressure decline.

Gender and Nightshift Work: A Cross Sectional Study on Sleep Quality and Daytime Somnolence.

A few studies suggested that female nightshift workers suffer more frequently from sleep deprivation and insomnia. We conducted a cross-sectional survey in two different occupational settings to address gender-related differences in nightshift work adaptation. We used the Epworth Sleepiness Scale and the Pittsburgh Sleep Quality Index questionnaires to quantify daytime sleepiness and sleep quality among 156 workers, 91 from a ceramic tile factory and 65 healthcare workers, including hospital doctors, nurses, and nurse assistants. Seventy-three percent of participants (40 women and 74 men) were engaged in nightshift work. We used logistic regression analysis to predict daytime sleepiness and poor sleep quality as a function of personal and lifestyle variables and nightshift work. The female gender showed a strong association with both daytime sleepiness and poor sleep quality. Results were also suggestive of an increase in the risk of daytime sleepiness associated with nightshift work and being married. Our results confirm that women are especially vulnerable to sleep disruption. Promoting adaptation to nightshift work requires special attention towards gender issues.

Adverse Health Effects Related to Shift Work Patterns and Work Schedule Tolerance in Emergency Medical Services Personnel: A Scoping Review.

Paramedicine as a profession is continually evolving in clinical practice, responsibilities, and workload. Changes over time in both population demographics and distribution have altered the demand for, and availability of, prehospital emergency medical services (EMS). These factors may also affect scheduling policies in many EMS organizations. However, there is little evidence that suggests optimal shift scheduling patterns to reduce adverse health events such as increased stress or fatigue in prehospital emergency health care providers. Our objective was to describe associations between variations in shift scheduling patterns and EMS provider health outcomes, such as fatigue, stress, sleep quality, and general mental and physiological health. We also sought to identify knowledge gaps. We performed searches of PubMed, CINAHL, Embase, and Cochrane databases for primary studies, systematic reviews, and meta-analyses published between January 2000 and December 2020. Studies reporting measurable health care outcomes in prehospital personnel with defined shift schedule patterns in land-based ambulance systems were included. Our search strategy yielded 188 studies, of which 11 met eligibility criteria (eight cross-sectional surveys, one single case report, one retrospective cohort study, one prospective cohort study, and one systematic review), with one additional study found through reference list screening, leaving 12 studies for review. All publications contained a description of shift schedule characteristics and shared similar outcomes of interest, although there was variation in comparators and assessment of outcomes. Most studies showed high rates of fatigue, stress, mental health concerns, and negative general health outcomes in paramedic shift worker populations. The case study reported improved fatigue, alertness, and sleep quality levels following a switch from a 24-hour shift pattern to an eight-hour shift. We did not complete an in-depth risk of bias assessment for any of the studies. Melnyk evidence ratings varied from IV to VI, indicating a low quality of evidence evaluating the impacts of shift schedule patterns in paramedics, with the retrospective cohort study design, ranked as IV, systematic review as a V, and prospective cohort study, case report and surveys ranked as VI. The low quality and quantity of evidence indicate the need for further research to definitively assess relationships between specific schedule patterns and health outcomes.

The 5-HTTLPR rs25531 LALA-genotype increases the risk of insomnia symptoms among shift workers.

BACKGROUND: Previous studies indicate that shift work tolerance may be associated with individual factors including genetic variability in the gene encoding the serotonin transporter 5-HTT (SLC6A4). The present study aimed to explore the interaction between work schedule (shift work versus non-shift work), genetic variability in SLC6A4 and insomnia symptoms. METHODS: The study was based on a national probability sample survey of 987 Norwegian employees drawn from The Norwegian Central Employee Register by Statistics Norway. Insomnia symptoms were assessed by three items reflecting problems with sleep onset, sleep maintenance, and early morning awakenings. Genotyping concerning SLC6A4 (the 5-HTTLPR S versus L and the SNP rs25531 A versus G) was carried out using a combination of gel-electrophoresis and TaqMan assay. RESULTS: Using the LALA genotype as a reference a main effect of the SS genotype (B = 0.179; 95% CI = 0.027-0.330) was found. In addition, a main effect of work schedule (0 = non shift, 1 = shift work) was found (B = 0.504; 95% CI = 0.185-0.823). The genotype x work schedule interaction was significant for all genotypes; SLA (B = -0.590; 95% CI = -0.954-0.216), LALG (B = -0.879; 95% CI = -1.342-0.415), SLG (B = -0.705; 95% CI = -1.293-0.117) and SS (B = -0.773; 95% CI = -1.177-0.369) indicating higher insomnia symptom scores among LALA-participants compared to participants with other genotypes when working shifts. CONCLUSIONS: The ability to cope with shift work is associated with the combination of the SLC6A4 variants 5-HTTLPR and SNP rs25531. Our findings demonstrated that the LALA-genotype increases the risk of insomnia symptoms among shift workers.

Reduced Tolerance to Night Shift in Chronic Shift Workers: Insight From Fractal Regulation.

Study Objectives: Healthy physiology is characterized by fractal regulation (FR) that generates similar structures in the fluctuations of physiological outputs at different time scales. Perturbed FR is associated with aging and age-related pathological conditions. Shift work, involving repeated and chronic exposure to misaligned environmental and behavioral cycles, disrupts circadian coordination. We tested whether night shifts perturb FR in motor activity and whether night shifts affect FR in chronic shift workers and non-shift workers differently. Methods: We studied 13 chronic shift workers and 14 non-shift workers as controls using both field and in-laboratory experiments. In the in-laboratory study, simulated night shifts were used to induce a misalignment between the endogenous circadian pacemaker and the sleep-wake cycles (ie, circadian misalignment) while environmental conditions and food intake were controlled. Results: In the field study, we found that FR was robust in controls but broke down in shift workers during night shifts, leading to more random activity fluctuations as observed in patients with dementia. The night shift effect was present even 2 days after ending night shifts. The in-laboratory study confirmed that night shifts perturbed FR in chronic shift workers and showed that FR in controls was more resilience to the circadian misalignment. Moreover, FR during real and simulated night shifts was more perturbed in those who started shift work at older ages. Conclusions: Chronic shift work causes night shift intolerance, which is probably linked to the degraded plasticity of the circadian control system.

Inter-individual differences in sleep response to shift work in novice police officers - A prospective study.

The aim of this longitudinal study on novice police officers was to investigate inter-individual differences in sleep response to shift work, and to identify potential baseline predictors thereof. A total of 42 subjects were assessed at baseline, prior to commencing shift work. They were re-assessed during three follow-up sessions within the first 2 years of shift work exposure after approximately 4, 12, and 20 months of rotating shift work. Wrist actigraphy and sleep logs were used to investigate nocturnal sleep at baseline and daytime sleep after night shifts during the follow-up sessions. Actigraphically estimated total sleep time and subjective sleep quality were analyzed as outcome variables, using mixed-effects analysis of variance. Systematic inter-individual differences were observed in the overall response of these outcome variables to shift work. In this sample, flexibility of sleeping habits and gender were found to be predictors of daytime total sleep time in the first 2 years of shift work exposure. Flexibility of sleeping habits and subjective quality of nighttime sleep prior to shift work were found to be predictors of subjective quality of daytime sleep. These results suggest that it may be possible to detect and even predict sleep deficiencies in response to shift work early on, which could be a basis for the development of individualized interventions to improve shift work tolerance.

Individual differences in the cortisol-awakening response during the first two years of shift work: A longitudinal study in novice police officers.

Cortisol acts as a critical biological intermediary through which chronic stressors like shift work impact upon multiple physiological, neuro-endocrine and hormonal functions. Therefore, the cortisol awakening response (CAR) is suggested as a prime index of shift work tolerance. Repeated assessments of the CAR (calculated as MnInc) in a group of 25 young novice police officers showed that in the interval between about 4 and 14 months after transitioning from regular day work to rotating shift work, mean values began to rise from baseline to significantly higher levels at about 14 months after they commenced shift work. Visual inspection of the individual trends revealed that a subgroup of 10 subjects followed a monotonically rising trend, whereas another 14 subjects, after an initial rise from about 4-14 months, reverted to a smaller, baseline level cortisol response at about 20 months after the start of shift work. If the initial increase in the cortisol response marks the development of a chronic stress response, the subsequent reversal to baseline levels in the subgroup of 14 participants might be indicative of a process of recovery, possibly the development of shift work tolerance.