• Korean Journal of Psychosomatic Medicine
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• v.29 no.2
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• pp.111-120
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• 2021

Objectives : Shift work has been known to cause various health problems by making it difficult for humans to adapt to their natural circadian rhythms. In particular, shift workers tend to complain of sleep difficulties associated with work schedules, and sometimes use alcohol as a self-medication to induce sleep. To date, no clear mechanism has been identified regarding the link between shift work and sleep, between shift work and drinking. This study aims to confirm the relationship between shift work and sleep, and to analyze whether the change in sleep caused by shift work causes drinking. Methods : This study included 11360 people (5704 men and 5656 women) among the Korean National Health and Nutrition Survey data in 2014, 2016 and 2018. The work type between 6am-6pm was defined as day work, and other work types were defined as shift work. Using logistic regression analysis, the relationship between shift work and sleep quality, shift work and high risk drinking, drinking amount at 1 time, drinking frequency were analyzed. In addition, we analyzed whether sleep mediates the relationship between shift work and drinking using mediated analysis. Results : Shift work showed a significant negative relationship with sleep quality in men and women (male OR=1.37, 95% CI 1.11-1.70, female OR=1.26, 95% CI=1.05-1.50). There was no significant relationship between shift work and alcohol in the case of men, but in the case of women, there was a significant positive relationship between shift work and the number of alcohol consumption (OR=1.34, 95% CI=1.04-1.72). When mediation analysis was conducted, it was found that women's sleep quality partially mediated the relationship between shift work and the frequency of drinking. Conclusions : The results of this study suggest that shift work causes sleep difficulties, and in the case of women, drinking can be induced through the partial mediating effect of sleep. Considering that women are more likely to choose drinking as a coping method for sleep problems, more active interventions for female shift workers are needed.

• 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.

• Safety and Health at Work
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• v.10 no.4
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• pp.512-517
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• 2019

Background: Rest breaks at work are reported to reduce fatigue and job stress. Apartment janitors in Korea who perform night shift work and work long hours can be exposed to various health problems (HPs). However, few studies have evaluated relationships between their rest breaks and HPs. This study was conducted to examine the relationships between long working hours, shift work, and insufficient rest breaks and HPs among Korean apartment janitors. Methods: Data on 1,212 selected male apartment janitors were obtained from the 3rd and 4th Korean Working Conditions Surveys. Demographic and occupational characteristics were collected using self-reported questionnaires. Rest breaks at work were classified as "sufficient" or "insufficient." Long working hours were considered as working more than 60 hours per week. Zero-inflated negative binomial (ZINB) regression was performed to investigate the effects of shift work and long working hours on HPs and the effects of rest breaks on relationships between HPs and long working hours and shift work. Results: Among those with insufficient rest breaks at work, significant associations were found between long working hours and the risk of HPs [odds ratio (OR) = 1.489; 95% confidence interval (CI) = 1.038-2.136] and work-related HPs (WRHPs) [OR 1.621; 95% CI = 1.156-2.272], and between shift work and HPs [OR = 1.603; 95% CI = 1.084-2.372]. These relationships became nonsignificant when sufficient rest breaks were provided. Conclusion: It is important to provide breaks at work to reduce HPs because of long working hours and shift work among aged workers such as apartment janitors.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.550-561
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• 2019

Objectives: The purpose of this study is to provide basic data for the improvement of the working environment for health prevention and related countermeasures for shift workers. This study was conducted based on the Fifth Korean Working Conditions Survey (KWCS), which analyzed the health effects of shift work forces and compared them with preceding studies. Methods: By analyzing secondary rates using raw data from the 5th KWCS, 4,870 (9.7%) of the 50,184 total study subjects were divided into shift work and 45,314 (90.3%) non-shift work groups based on the response to shift status. Variables that could affect work health issues were identified and corrected. A cross-analysis was conducted to examine demographic characteristics (gender, age, and education level) of the workers and occupation characteristics (monthly net earnings, employment type, occupation, working period up to now, workplace scale, type of work system, and weekly working hours). In order to find the work health issue ratio between the shift and non-shift work groups, logistic regression was analyzed and the association with health problems according to shift type by gender was looked at through cross-analysis. Results: According to the surveys conducted from the 1st KWCS (2006) to the 5th KWCS (2017), the proportion of shift workers continued to increase. Also, muscular pains in the lower limbs (hips, legs, knees, feet, etc.) (OR=1.135, 95%CI 1.031-1.251), headaches, eyestrain (OR=1.580, 95% CI 1.428-1.748), anxiety (OR=1.715, 95% CI 1.402-2.099), difficulty falling asleep (OR=1.391), and other problems (OR=7.392) were reported. In addition, back pain, muscular pains in shoulders, neck and/or upper limbs, muscular pains in lower limbs (hips, legs, knees, feet, etc.), headaches, eyestrain, depression, anxiety, overall fatigue resulted in significant results for both male and female shift workers. Depression and anxiety were higher in female shift/circulation compared to males. Conclusions: The social nets for the health and safety of shift workers should be explored in a variety of ways, including management and supervision of shift sites, attempts to reorganize and improve the shift system, development of workers' health recovery programs, promotion, systematic treatment, and compensation systems.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.21 no.4
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• pp.403-412
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• 2014

Purpose: Shift work disrupts the synchronization between the human biological clock and the environment. Sleep disturbances are common for shift work nurses, and may threaten patient safety. This study was done to investigate the sleep characteristics and medication errors (ME) of intensive care unit (ICU) nurses who work shifts, and ascertain if there is an association between these factors. Methods: Data were collected using a self-report questionnaire from 126 ICU nurses on three shifts. Collected data included their sleep characteristics including sleep patterns and sleep disturbances, and ME for the past 2 weeks. Results: There were significant differences in sleep duration and sleep latency according to shift. Day shift nurses had the shortest sleep duration, and their sleep latency was the longest (about 49 minutes) compared to nurses on evening and night shifts; 54% reported sleep disturbances, 16% experienced ME, and among these nurses 50% were on the night shift. Logistic regression analysis revealed significant associations between nurses' sleep duration and ME (adjusted OR 0.52 [95% CI 0.32-0.85]). Conclusions: The results confirmed that shift work nurses in the ICUs experience sleep disturbance, and that less sleep is associated with ME.

• Journal of Nutrition and Health
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• v.47 no.6
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• pp.416-425
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• 2014

Purpose: The purpose of this study was to investigate the stress, dietary habits, dietary behaviors, and health-related behavior of nurses. Method: The subjects of this study were 161 nurses studying at a cyber university. The general characteristics, stress, dietary habits, dietary behaviors, and health-related behavior of the subjects were surveyed using a self-administered questionnaire in October, 2010. The subjects were divided into two groups according to the working pattern: shift workers (n = 110) and non-shift workers (n = 51). Results: In the general characteristics, there were significant differences in marriage, monthly income, employment type, and job satisfaction between the two groups. Total stress score did not differ significantly between the two groups. In dietary habits, significant differences in meal regularity, skipping meals, skipping reasons, having regular mealtimes, frequency of snack and the snack time between shift workers and non-shift workers (p<0.05). Total score of dietary behaviors in shift workers was significantly lower than that in non-shift workers (p<0.05). Score of shift workers in taking three meals per day regularly was significantly lower than that of non-shift workers. In health-related behavior, a significant difference in sleeping time was observed between shift workers and non-shift workers. Dietary behavior showed negative correlation with shift work (r = 0.176) and positive correlation with health consciousness (r = 0.210) and perceived health status (r = 0.198) in subjects after adjustment for age, marriage, monthly income, and employment type (p < 0.05). Multiple regression analysis revealed that shift work, health consciousness, and perceived health status affected dietary behavior in subjects. Conclusion: These results indicate that shift working nurses had poor dietary habits and dietary behaviors, and these dietary behaviors are affected by their shift work, health consciousness, and perceive health status.

• Culinary science and hospitality research
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• v.14 no.4
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• pp.339-356
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• 2008

The purpose of this study is to provide the developmental basic data of a change in shift work types by making a self-administered survey of the effect of commitment by shift work and the open kitchen system on job satisfaction and job stress, and mutual relation between variables on 287 cooks in luxury hotels. Analysis showed that the operation of the shift work system was effective in reducing the internal stress of the cooks, their external stress, or their self-uncertainty on the job, and the business by the open kitchen system was effective in raising self-esteem. In addition, job commitment by shift work and the open kitchen system were effective in promoting the job satisfaction of employees, interpersonal relations, promotion, benefits and wages. Consequently, the decrease of external and internal stress or self-uncertainty and the improvement of job satisfaction can be connected with the increase of productivity or cost reduction. Therefore, the open kitchen system should be properly applied to the shift work system, along with sanitation, safety and the periodic checkup of kitchen.

• Research in Community and Public Health Nursing
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• v.18 no.2
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• pp.284-292
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• 2007

Purpose: The purpose of this study is to explore and understanding the nature of the shift workers' experience in industries requiring 24 hours-a-day service provision and support. For the Purpose, the present researcher made a research Question, "What are workers' experience in the shift work?" Methods: In the study, 5 male shift workers, 3 female shift worker and a woman (key informant) whose husband is a shift worker participated. Then profound interviews with the participants were made after their agreement. Results: The researcher classified the significant statements under 6 theme clusters, 1) sense of difference; 2) worries about health; 3) draining of emotion; 4) anxiety; 5) sadness; and 6) being comfortable. Conclusions: Shift work which is inevitable in modern society may have severe influences on shift workers' physical, mental and psychological aspects by causing their work cycle rhythm to be unbalanced. Finally, the researcher hopes that the results of the study would help understand workers' life and increase social concern and support to the workers.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.3
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• pp.321-330
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• 2020

Objectives: The purpose of this study was to compare vitamin D levels, sleep quality, and anxiety symptoms between shift workers and daytime workers and analyze the mediating effect of vitamin D and sleep quality between shift work and anxiety symptoms. Methods: The subjects of the study were 6744 people who received a medical examination while working for an electronics manufacturing company in 2016. We evaluated their shift work, vitamin D levels, sleep quality, and anxiety symptoms with blood samples and questionnaires. Chi-square test, t-test and path statistical analysis were performed. Results: The shift workers had significantly higher symptoms of anxiety than the day workers, significantly lower levels of vitamin D in the blood, and significantly poorer quality of sleep. The results of the pathway analysis confirmed that blood vitamin D and sleep quality had a mediating effect between shift work and anxiety symptoms. Conclusions: Shift workers should be constantly paying attention to mental health effects such as anxiety symptoms. Shift workers should also be alerted of the risk of vitamin D deficiency, encouraged about sun exposure and vitamin D intake, and required to undergo training and counseling on sleep hygiene.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.188-196
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• 2005

Accident reports from 1991 to 2000 of a steel company were used to analyze which factors induce industrial accidents. The subjects were 8,311 blue-collar workers, who sustained 114 occupational injuries and work on a continuous full-day 3-team 3-shift system of backward rotation(mornings to afternoons to nights). With respect to marital status, the occupational injury rate(OIR) on the married workers was significantly higher compared to unmarried workers. With respect to no, the OIR of those in their early 20s was significantly higher when compared to other age groups. The OIR of highly educated workers showed a reduction when compared with lower educated workers. The OIR of shift workers were significantly higher compared with the daytime workers. The OIR of type of work decreased across the steel manufacturing process, rolling process, machine maintenance section forwarding products section to the field management section. With respect to the block of shift work(morning, afternoon, and night shifts) by the type of work, the OIR of the night shift was higher than those of the morning shift in the steel manufacturing process or forwarding products section. The OIR of the machine maintenance section was slightly higher in the morning shift than those of the night shift. The OIR of the time of day of the shift workers reached a peak between 09:00 and 11:00. The OIR of a slight injury to shift workers decreased across the night, afternoon, to morning shifts whereas the OIR of a serious injury tended to decrease across the night, morning, to afternoon shift. The body parts most commonly injured were the arm and the crus.