• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.41.1-41.11
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• 2023

Background: Shift work has been reported to have several harmful effects on the human body. However, a small number of studies have evaluated the association between shift work and adverse effects on the thyroid. In our longitudinal study, we examined the causal association between shift work and the risk of hypothyroidism. Methods: A Kangbuk Samsung Cohort Study was conducted on 112,648 men without thyroid disease at baseline who were followed up at least once between 2012 and 2019. Shift work status and shift schedule types were categorized using standardized questionnaires. Hypothyroidism was defined using the reference ranges of serum thyroid-stimulating hormones and free thyroxine levels. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident hypothyroidism were estimated using Cox proportional hazards regression analyses with the daytime work group as the reference. Results: During the 501,237 person-years of follow-up, there were 6,306 incident cases of hypothyroidism (incidence density, 1.26 per 100 person-years). The multivariable-adjusted HR of incident hypothyroidism for the shift work total group that included all shifts compared with the daytime work group was 1.27 (95% CI: 1.15-1.40). For the fixed evening, fixed night, rotating shift, and other shift workers, the multivariable-adjusted HRs (95% CI) were 1.11 (0.76-1.61), 2.18 (1.20-3.93), 1.39 (1.23-1.56), and 1.00 (0.82-1.22), respectively. In subgroup analyses by age, the association between shift work and hypothyroidism was more pronounced in younger participants (< 40 years; HR: 1.31; 95% CI: 1.16-1.47). Conclusions: Our large-scale cohort study showed an association between shift work and the incidence of hypothyroidism, especially in younger workers with night shifts.

• Journal of Preventive Medicine and Public Health
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• v.54 no.1
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• pp.46-54
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• 2021

Objectives: This study explored the relationship between shift intensity and insomnia among hospital nurses. Methods: The participants were 386 female hospital nurses who underwent a special health examination for night workers in 2015. The Korean Insomnia Severity Index (ISI), indices of shift work intensity, and other covariates such as amount of exercise, level of alcohol consumption, employment duration, and hours worked were extracted from the health examination data. The indices for shift intensity were (1) number of 3 consecutive night shifts and (2) number of short recovery periods after a previous shift, both assessed over the prior 3 months. Multiple logistic regression analysis adjusted for the aforementioned covariates was performed to evaluate the association of shift intensity with insomnia, defined as an ISI score of ≥8. Results: The nurses with insomnia tended to be younger (p=0.029), to have worked 3 consecutive night shifts more frequently (p<0.001), to have experienced a greater number of short recovery periods after the previous shift (p=0.021), and to have worked for more hours (p=0.006) than the nurses without insomnia. Among the other variables, no statistically significant differences between groups were observed. Experiences of 3 or more consecutive night shifts (odds ratio [OR], 2.33; 95% confidence interval [CI], 1.29 to 4.20) and 3 or more short recovery periods (OR, 2.01; 95% CI, 1.08 to 3.73) were associated with increased odds of insomnia. Conclusions: The results suggest that decreasing the shift intensity may reduce insomnia among hospital nurses working rotating shifts.

• Journal of Korean Academy of Nursing
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• v.21 no.2
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• pp.129-149
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• 1991

Circadian rhythm is entrained in the 24-hour time interval by periodic factors in the environment, known as zeitgeber. But most rotating work schedules are outside the range of the entrainment of the pacemaker timing the human circadian sleep - wake cycle. It has been postulated that physiological and emotional disturbances occur in most human functions when the circadian rhythm is disturbed. So application of circadian principles to the design of shift schedules can aid in maintaining the temporal integrity of the circadian system and thereby minimize for the shift worker any detrimental consequences of circadian disruption. This study was a quasi-experimental study to test the effect of shift intervals for the clinical nurse on the circadian rhythm. Twenty nurses newly employed in general units of two hospitals were selected as an experimental group and twelve college nursing students as a control group. Both groups were selected according to an established criteria using a purposive sampling technique. Ten subjects were assigned to a weekly shift group and another ten to a biweekly shift group engaged in a semi -continuous shift schedule(sunday off) with a backward direction, that is, morning -evening - night shift. The control group worked a morning shift for 42 days. Oral temperature rhythm, waking tim, sleep - wake cycle, fatigue, and mental performance were measured during the experimental period. The data collection period was from April 30, 1990 to June 10, 1990. MANOVA, paired t-test, ANOVA, and Student Newman Keuls method were used for statistical analysis. The results are summarized as follows. 1. Phase delay in the acrophase of temperature rhythm was shown according to the backward rotating shift. A complete adaptation to work on the night shift was achieved between the sixth and ninth day of the night shift. 2. There was no difference in either waking time or sleep- wake cycle according to the duration of the working day for every shift group. Significant difference was found in the waking time and the sleep -wake cycle for subjects on the morning, evening, and night shift in both of the shift groups(weekly shift group : λ＝0.121, p＜0.01, λ＝0.112, p＜0.01, biweekly shift group : λ＝0.116, p＜0.01, λ＝0.084, p＜0.01). 3. There was no difference in fatigue between the first working day and the last working day for the control group and for the biweekly shift group. In the weekly shift group, physical fatigue was significantly different for the first day and the sixth day of the night shift(t＝-2.28, p＜0.05). Physical fatigue and total fatigue on the first day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝5.79, p＜0.01, F＝4.56, p＜0.05). There was a significant difference between the shift groups and the control group(p＜0.05), Physical fatigue, neurosensory fatigue and total fatigue on the last day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝12.65, p＜0.01, F＝7.77, p＜0.01, F＝9.68, p＜0.01). There was a significant difference between the shift groups and the control group(p＜0.05). 4. No difference in mental performance was seen between the first day and the last day of work in each case. An arithmatic test on the first day of the night shift revealed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝3.79, p＜0.05). There was a significant difference between the shift groups and the control group(p＜0.05) . The digital symbol substitution test and the arithmetic test on the last day of the night shift showed a significant difference among the control group, the weekly shift group, and the biweekly shift group(F＝3.68, p＜0.05, F＝5.55, p＜0.01), and both showed a significant difference between the shift groups and the control group(p＜0.05). Accordingly, this study showed that during night duty, the waking time, sleep- wake cycle, and fatigue increased and mental performance decreased compared with morning and evening duty. It was also found that the weekly shift group had a higher fatigue score on the sixth day of night duty as compared to the -first day, but the waking time, sleep- wake cycle, and mental performance revealed no difference for the duration of the night duty or between shift groups, and complete adaptation of temperature rhythm was achieved between the sixth and ninth day of night duty. It is possible to conclude from these results that for intermediate circadian type in a healthy young woman, a biweekly shift system is more compatible with the circadian timing system than weekly shift system.

• Sleep Medicine and Psychophysiology
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• v.26 no.2
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• pp.111-124
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• 2019

Objectives: Healthy sleep is important and can have a positive effect on resilience. The aim of the present study was to compare the differences in resilience between two group nurses in rotating shift and daytime fixed work schedules and to investigate stress perception, coping factors, social and psychological health, and sleep factors that may affect resilience. Methods: A total of 400 female nurses having rotating shift and daytime fixed work schedules at two hospitals was surveyed from June 12, 2017 to June 12, 2018. All participants completed perceived stress scale (PSS), stress coping short form (Brief COPE), psycho-social wellbeing Index short form (PWI-SF) or general health questionnaire-18 (GHQ-18), center for epidemiologic studies depression scale (CES-D), STAI-X-1 in state-trait anxiety inventory (STAI), Pittsburgh sleep quality index (PSQI), Epworth sleepiness scale (ESS), insomnia severity index (ISI), Conner Davidson resilience scale (CD-RISC). Independent t-test, paired t-test, Pearson correlation analysis, and multiple regression analysis were applied to the results of the final 373 questionnaires of 400 nurses in two general hospitals. Results: Comparing the variable statistics between the two groups of rotating shift and daytime fixed work nurses, showed statistically significant differences in all variables except perceived stress, sleep quality, and daytime sleepiness. Factors that had a significant correlation with resilience were stress coping strategies, depression, and insomnia severity (p < 0.001). In multiple regression analysis, larger positive reframing1 (β = 0.206, p < 0.001), severe less depression (β = -3.45, p < 0.001), and higher psychosocial health (β = 0.193, p < 0.001). As acceptance coping2 increased (β = 0.129, p < 0.05), as daytime sleepiness decreased (β = -1.17, p < 0.05), and as active coping2 increased (β = 0.118, p < 0.05), as the positive reframing2 increases (β = 0.110, p < 0.05), the resilience increased. Conclusion: This study, it was found that resilience was higher in daytime fixed workers than in shift workers. In addition, specific stress coping strategies, psycho-social health, sleep, and depression factors were associated with resilience.

• Journal of agricultural medicine and community health
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• v.38 no.4
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• pp.229-242
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• 2013

Objectives: The objective of this study was to identify the influence of shift work on sleep quality, daytime sleepiness, and perceived errors during nursing work among hospital nurses. Methods: The study subjects were 209 hospital nurses working in two general hospitals in South Korea. The data were collected through self-administered questionnaires in May 2013. Sleep quality was measured using Korea Pittsburgh Sleep Quality Index (PSQI-K), daytime sleepiness was measured using Epworth Sleepiness Scale (ESS), and perceived errors in past 6 months during nursing duty hours with the tool developed in this study. Results: The sleep quality was significantly worse among rotating shift nurses when compared to fixed day duty nurses. However, the odds ratio (OR) of 1.92 [95% confidence interval(CI): 0.58-6.37] adjusted for sociodemographic variables, health behaviors, and working environment in logistic regression was not significant. There was no significant difference in the daytime sleepiness between rotating shift nurses and fixed day duty nurses in both simple and multivariable analyses. There were significantly more perceived errors in rotating shift nurses than fixed day duty nurses. However, the OR of 1.26 (95% CI: 0.38-4.21) adjusted for sociodemographic variables, health behaviors, working environment, sleep quality, and daytime sleepiness in logistic regression was not significant. Depression (OR=3.31, 95% CI: 1.11-9.84) and daytime sleepiness(OR=1.18, 95% CI: 1.07-1.30) were significantly associated with perceived errors in logistic regression. Conclusion: This study suggested shift work among hospital nurses had no independent influence of sleep quality, daytime sleepiness, and perceived errors. However, daytime sleepiness had independent influence of perceived errors. More studies are warranted to achieve more reliable conclusion.

• Sleep Medicine and Psychophysiology
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• v.17 no.1
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• pp.28-33
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• 2010

Objectives: Working at other times than the regular day shift has been reported to be a stressor associated with health consequences and mental disorders as well as disturbance of sleep. In current study, we aimed at investigating the relationship between work schedule, sleep quality and depression among police officers. Methods: Eleven hundreds and forty five police officers (male: 1040, female: 105) completed questionnaires of basic socio-demographic data, Pittsburgh Sleep Quality Index (PSQI), Korean Scale of Occupational Stress (KOSS), Impact of Event Scale - Revised (IES-R) and Center for Epidemiologic Study-Depression (CES-D). Results: After controlling for age, sex and educational level, score of CES-D was correlated positively with the score of KOSS, PSQI and IES-R on partial correlation analysis (r=-0.077; p=0.009, r=0.262; p<0.000 and r=0.421, p<0.000, respectively). Logistic regression analysis revealed that female sex, age, the score of KOSS and IES-R and schedule of rotating shift work predicted higher score than 16 score of CES-D significantly in total subjects (p=0.023, p=0.015, p=0.000, p=0.000 and p=0.022, respectively). Conclusion: Current result suggested that not only female sex, age, higher occupational stress and impact of event scale but also rotating shift work schedule might be related to depression among police officers.

• Korean Journal of Occupational Health Nursing
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• v.7 no.2
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• pp.155-163
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• 1998

In order to investigate the effects of rotating shift work on the subjective characteristics of sleep and mental depression questionnaire survey was carried out on 405 shift workers and 153 nonshift workers who were nurses employed. in three university hospital. The questionnaire forms used in this study were the self rating depression scale(SDS) and circadian type questionnaire(CTQ) factor R(rigidity/flexbility of sleeping habit) and factor V(inability/ability to overcome drowsiness). The results were as follows ; 1. Mean score of CTQ R in shift workers was significantly lower than that in nonshift workers, however, no significant difference in CTQ V was observed between two groups. 2. Mean score of SDS was significantly higher in shift workers(44.1) than in nonshift workers(39.8). 3. Mean self rating depression scale scores of pervasive affect, physiologic equivalents and psychological equivalents were significantly higher in shift workers than in nonshift workers. 4. In shift worker, mean SDS score was the highest in confusion and followed by diurnal variation, retardation, and indeciveness in the descending order. In nonshift worker, that score was the highest in decreased libido and followed by confusion, and indeciveness in the descending order. 5. Circadian type questionnaire scores was significantly and negatively correlated with significantly and negatively correlating with Self-rating depression scale scores(r=-0.473).

• Journal of Korean Academy of Nursing
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• v.47 no.4
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• pp.476-487
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• 2017

Purpose: This study aimed to examine the effects of cognitive behavior therapy for insomnia (CBT-I) based on the mobile social networking service (SNS) on dysfunctional beliefs and attitudes about sleep, sleep quality, daytime sleepiness, depression, and quality of life among rotatingshift nurses in a hospital in Korea. Methods: A nonequivalent control group pre-post test design was used. The participants included 55 nurses with rotating three-shift work (25 in the experimental group and 30 in the control group). For the experimental group, CBT-I using mobile SNS was provided once a week for 60 minutes over six weeks. Data were analyzed using descriptive statistics, $x^2-test$, independent samples t-test, and Mann-whitney U test with the SPSS 21.0 program. Results: In the homogeneity test of the general characteristics and study variables, there were no significant differences between the two groups. Nurses in the experimental group had significantly lower scores on dysfunctional beliefs and attitudes regarding sleep and sleepiness than nurses in the control group. Nurses in the experimental group had significantly higher scores on sleep quality and quality of life than nurses in the control group. Conclusion: These findings indicate that using the mobile SNS-based CBT-I is feasible and has significant and positive treatment-related effects on rotating-shift nurses' irrational thoughts and beliefs in association with sleep, sleep quality, daytime sleepiness, and quality of life. These contribute to expanding our knowledge of rotating-shift nurses' sleep issues and their preferences for intervention.

• Safety and Health at Work
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• v.12 no.3
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• pp.359-364
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• 2021

Aim: We aimed to examine the cross-sectional and longitudinal associations between sleep and work-related impaired cognitive and emotional functioning in police employees. Methods: This study included 410 participants (52% men) employed in a police district in Norway at baseline, of which 50% also participated in the study at 6 months later follow-up. The questionnaires included items measuring work schedule, sleep length, insomnia, as well as impaired cognitive and emotional functioning at work. Results: The results showed that insomnia was related to impaired work-related emotional functioning measured at baseline, and to impaired cognitive functioning measured at both baseline and follow-up. Sleep length and rotating shift work were not associated with future decline in cognitive or emotional functioning. Conclusion: Our study indicates that the relationship between insomnia and emotional functioning at work may be transient, whereas insomnia can be related to both immediate and future impaired cognitive functioning. Replication of the findings in larger samples is advised. The findings call for an emphasis on the prevention and treatment of sleep problems among police employees as a mean of maintaining and improving cognitive and emotional functioning at work, and thereby reducing the risk for impaired performance and negative health and safety outcomes.

• Journal of the Ergonomics Society of Korea
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• v.24 no.2
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• pp.57-63
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• 2005

Ergonomic intervention techniques were adopted to assess and control potential risk factors of work-related musculoskeletal disorders(WMSDs) in the automated light assembly manufacturing system. Ten different kinds of assembly workstations implemented with a conveyor system and twelve female workers were observed and evaluated with careful video film analysis. Several close examinations using sets of checklists established by qualified safety and health organizations, such as NIOSH, OSHA, and ANSI, were conducted and every workers and staffs in the site participated in the self-report questionnaires and off-line interviews. Typical risk factors and symptoms of the upper extremity musculoskeletal disorders were found and categorized into specific parts of body. To reduce risk factors of WMSDs and improve system productivity new revised workstation standards, physical dimensions, were suggested accordant with anthropometric characteristics of workers and a heuristic decision strategy of rotating shift work schedules according to work contents has proposed to mitigate cumulative physical stress. Finally, ergonomic programs of entire company to prevent WMSDs were structured.