• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.2.1-2.14
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• 2022

Background: Because income and working hours are closely related, the health impact of working hours can vary according to economic status. This study aimed to investigate the relationship between working hours and the risk of poor self-rated health according to household income level. Methods: We used the data from the Korea National Health and Nutrition Examination Survey VI and VII. The information on working hours and self-rated health was obtained from the questionnaire. After stratifying by household income level, the risk of poor self-rated health for long working hour group (≥ 52 hours a week), compared to the 35-51 working hour group as a reference, were calculated using multiple logistic regression. Results: Long working hours increased the risk of poor self-rated health in the group with the highest income, but not in the group with the lowest income. On the other hand, the overall weighted prevalence of poor self-rated health was higher in the low-income group. Conclusions: The relationship between long working hours and the risk of poor self-rated health varied by household income level. This phenomenon, in which the health effects of long working hours appear to diminish in low-income households can be referred to as the 'poor worker's long working hours paradox'. Our findings suggest that the recent working hour restriction policy implemented by the Korean government should be promoted, together with a basic wage preservation to improve workers' general health and well-being.

• 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.

• Safety and Health at Work
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• v.14 no.4
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• pp.483-487
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• 2023

The objectives of the study were to explore the employment factors associated with long working hours, known as a risk factor for various health outcomes. The study relied on the national representative data of the 2013 French working conditions survey and a study sample of 23,378 full-time employees. Long working hours were defined by the threshold of 48 hours a week following the European Working Time Directive. The prevalence of long working hours was higher among men (13.5%) than among women (8.5%). Employees of the private sector, with permanent work contract, in small companies, and men in the services had a higher prevalence of exposure. This prevalence increased with educational and occupational levels. Our findings may help decision-makers to define preventive strategies. More research is needed to improve our knowledge of the employment factors associated with long working hours, as there may be strong differences between countries.

• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.21.1-21.11
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• 2023

Background: Recently, irregular working hours have become controversial issues in Korea. The health impact of irregular working hours on the work-related musculoskeletal pain (MSP) is scarcely researched before. We sought to investigate the association between irregular working hours and work-related MSP among South Korean workers. Methods: This study used data from the sixth Korean Working Conditions Survey in 2020. The prevalence of work-related MSP was analyzed using the χ² test. A multiple logistic regression analysis was conducted to assess the association between irregular working hours and work-related MSP. We conducted stratified analysis by gender, weekly working hours, and workers' control over their working hours. We calculated the adjusted odds ratios (ORs) of work-related MSP for irregular working hours combined with weekly working hours. Results: The OR for work-related MSP was significantly higher in the population with irregular working hours than in the population with regular working hours (OR: 1.43, 95% confidence interval [CI]: 1.29-1.58). Irregular and long (> 52 hours/week) working hours have the highest risk of work-related MSP in both genders (in men, OR: 3.48 [95% CI: 2.53-4.78]; in women, OR: 2.41 [95% CI: 1.46-4.00]). Conclusions: Irregular working hours were associated with work-related MSP in Korea. The association was magnified with long working hours. Reform of the Korean Labor Standards Act leading to increase irregular working hours may induce adverse health outcome.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.2
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• pp.236-243
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• 2015

Objectives: This study sought to examine the association between long working hours and depressive symptoms among interns and residents in South Korea. Methods: We analyzed a cross-sectional survey of 1,661 interns and residents from the 2014 Korean Interns & Residents Survey. Total working hours during the preceding week was assessed and classified into five categories(i.e. less than 60 hours, 60-79 hours, 80-99 hours, 100-119 hours, and 120-168 hours). Depressive symptoms during the previous week were measured by using ten items from the Center for Epidemiologic Studies Depression Scale questionnaire. Multivariate negative binomial regression was applied to examine the association between long working hours and depressive symptoms after adjusting for potential confounders, including medical specialty and training year. All analyses were performed using STATA/SE version 13.0. Results: 86%(N=1,429) of interns and residents worked 60 hours or more per week. Compared to the "less than 60 hours" group, long working hours for interns and residents were significantly associated with depressive symptoms: "60-79 hours"(PR: 1.56, 95% CI: 1.05, 2.32), "80-99 hours"(PR: 2.27, 95% CI: 1.54, 3.33), "100-119 hours"(PR: 2.62, 95% CI: 1.76, 3.89), and "120-168 hours"(PR: 3.28, 95% CI: 2.21, 4.86). Conclusions: This study found that long working hours were prevalent among interns and residents in South Korea, and it was associated with depressive symptoms.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.9.1-9.13
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• 2022

Background: Long working hours causes several health risks, but little is known about its effects on the liver. This study aimed to examine the correlation between working hours and abnormal liver enzyme levels. Methods: We used data from the Korea National Health and Nutrition Examination Survey IV-VII. For the final 15,316 study participant, the information on working hours was obtained through questionnaires, and liver enzyme levels, consisting of serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), through blood tests. The relationship between weekly working hours and abnormal levels of liver enzymes was analyzed using multiple logistic regression, and a trend test was also conducted. Results: In male, working ≥ 61 hours per week was significantly associated with elevated AST and ALT levels compared with working 35-52 hours per week. Even after adjusting for covariates, the odds ratios (ORs) of abnormal AST and ALT increased by 1.51 (95% confidence interval: 1.20-2.05) and 1.25 (1.03-1.52), respectively, and a dose-response relationship was observed. This association was more prominent among the high-risk group, such as those aged > 40 years, obese individuals, worker on non-standard work schedule, pink-collar workers, or temporary worker. No correlation was observed in female. Conclusions: Long working hours are associated with abnormal liver function test results in male. Strict adherence to statutory working hours is necessary to protect workers' liver health.

• Safety and Health at Work
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• v.12 no.4
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• pp.517-521
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• 2021

Background: This study aimed to investigate whether working long hours was related to infertility among female Korean workers, while taking age into consideration. Methods: We used data from the 2018 National Survey on Fertility and Family Health and Welfare in Korea that is a cross-sectional, nationally representative, and population-based survey. Infertility was defined as women who were not pregnant after regular unprotected intercourse for a year. Working long hours was classified as ≥52 hours, and subgroups as per age were classified on the basis of being younger or older than 40 years of age. Differences in infertility risk between the long working hour group and none were estimated in crude and fully adjusted logistic regression models with age-group stratification. Results: Of 5,909 Korean female workers, the crude and adjusted odds ratios (95% confidence intervals) of infertility for working long hours were 1.295 (0.948-1.737) and 1.303 (0.921-1.809), respectively. In the subgroup of patients below 40 years of age, the crude and adjusted odds ratios (95% confidence interval) were 1.957 (1.216-3.039) and 1.921 (1.144-3.120), whereas those aged 40 years or older had 0.994 (0.647-1.471) and 0.939 (0.560-1.501), respectively. The weighted prevalence of infertility increased as weekly working hours increased only for the younger than 40-year subgroup. Conclusions: Infertility is associated with working long hours, especially in young-aged workers. Thus, the working schedule must be structured to better suit young female workers.

• The Korean Journal of Health Service Management
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• v.9 no.1
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• pp.41-55
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• 2015

Working the night-shift and long working hours may be linked to insomnia. The purpose of this study is to determine the association between night-shift work and long working-hours with regard to subjective insomnia in Korean workers. This study was based on the Third Korean Working Condition Survey (KWCS) conducted on workers in 2011. The total number of individuals included in the analysis was 34,708 workers. Adjusted odd ratios showed statistically effective associations to insomnia. For night-shift work, the results were 2.71 (1.53 - 4.82) for night shift work by experts and managers, 2.95 (2.11 - 4.11) for night-shift work by officers, and 3.90 (2.05 - 7.42) for night-shift work by engineers compared with day duty. For long working hours, the scores were 2.43 (1.68-3.51) for >52 working hours by officers, 1.72 (1.15 - 2.58) for those in sales and service compared to ${\leq}40$ working hours. We suggest the need for Korean workers to target specific groups when creating policies related to reasonable environmental conditions.

• Safety and Health at Work
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• v.13 no.1
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• pp.17-22
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• 2022

Background: This study aimed to identify work-related risk factors, including long working hours and night/shift work, for unmet health care need using data of a representative panel of Korean adults. Methods: Associations between work-related factors and unmet health care need were analyzed using data of 3,440 participants (10,320 observations) from the 2011-2013 Korean Health Panel Study. A generalized estimating equation was used for the analysis of repeated measures. Results: The prevalence of unmet health care was 16.6%. After adjusting sex, age, socioeconomic status, work characteristics, and working more than 60 hours per week (odds ratio [OR]: 1.43, 95% confidence interval [CI]: 1.23-1.65) or 50-59 hours per week (OR: 1.26, 95% CI: 1.08-1.46) instead of 40-49 hours per week and night/shift work (OR: 1.27, 95% CI: 1.06-1.51) were associated with unmet health care need. Conclusion: Long working hours and night/shift work are risk factors for unmet health care need among the Korean working population.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.4.1-4.11
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• 2022

Background: Long working hours are known to account for approximately one-third of the total expected work-related diseases, and much interest and research on long working hours have recently been conducted. Additionally, as the prevalence of prediabetes and the high-risk group for diabetes are increasing worldwide, interest in prediabetes is also rising. However, few studies have addressed the development of type 2 diabetes and long working hours in prediabetes. Therefore, the aim of this longitudinal study was to evaluate the relationship between long working hours and the development of diabetes in prediabetes. Methods: We included 14,258 prediabetes participants with hemoglobinA1c (HbA1c) level of 5.7 to 6.4 in the Kangbuk Samsung Cohort Study. According to a self-reported questionnaire, we evaluated weekly working hours, which were categorized into 35-40, 41-52, and > 52 hours. Development of diabetes was defined as an HbA1c level ≥ 6.5%. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the development of diabetes were estimated using Cox proportional hazards analyses with weekly working 35-40 hours as the reference. Results: During a median follow-up of 3.0 years, 776 participants developed diabetes (incidence density, 1.66 per 100 person-years). Multivariable-adjusted HRs of development of diabetes for weekly working > 52 hours compared with working 35-40 hours were 2.00 (95% CI: 1.50-2.67). In subgroup analyses by age (< 40 years old, ≥ 40 years old), sex (men, women), and household income (< 6 million KRW, ≥ 6 million KRW), consistent and significant positive associations were observed in all groups. Conclusions: In our large-scale longitudinal study, long working hours increases the risk of developing diabetes in prediabetes patients.