Statement by the Korean Society of Occupational and Environmental Medicine on the proposed reform of working hours in South Korea.

The current 52-hour workweek in South Korea consists of 40 hours of regular work and 12 hours of overtime. Although the average working hours in South Korea is declining, it is still 199 hours longer than the Organisation for Economic Co-operation and Development average of 1,716 hours per year. In view to this, the South Korean government has now proposed to reform the workweek, mainly intending to increase the workweek to 69 hours when the workload is heavy. This reform, by increasing the labor intensity due to long working hours, goes against the global trend of reducing work hours for a safe and healthy working environment. Long working hours can lead to increased cerebrovascular and cardiovascular diseases, industrial accidents, mental health problems, and safety accidents due to lack of concentration. In conclusion, the Korean government's working hour reform plan can have a negative impact on workers' health, and therefore it should be thoroughly reviewed and modified.

Risk of insomnia symptoms according to Work-Family Conflict by workers' characteristics.

Background: Work-Family Conflict means that the demands of work and family roles cannot be met simultaneously, so one cannot concentrate on one's work or family role. This conflict can negatively affect mental health and cause insomnia symptoms. Methods: This study was conducted on 20,442 subjects. Insomnia symptoms were assessed using the Minimal Insomnia Symptom Scale, and other variables were assessed using the questionnaire method. Logistic regression analyses were performed to evaluate the effect of Work-Family Conflict on insomnia symptoms, and subgroup logistic regression analyses were also performed. Results: The number of people with insomnia symptoms was 4,322 (15.1%). Compared with Low Work-Family Conflict, the odds ratios (ORs) for the risk of insomnia symptoms were 1.84 (95% confidence interval: 1.56-2.16) in High work-to-family conflict, 1.16 (1.02-1.32) in High family-to-work conflict, and 3.19 (2.87-3.55) in High Work-Family Conflict. The ORs were higher for men than women in High WFC but higher for women than men in High Work-Family Conflict. Conclusions: The risk of insomnia symptoms was highest in High Work-Family Conflict.

Relationship between job rotation and work-related low back pain: a cross-sectional study using data from the fifth Korean working conditions survey.

BACKGROUND: Job rotation was introduced in various industries as a strategic form of work for improving workers' job skills and health management. This study aims to examine the relationship between job rotation and work-related low back pain (LBP), one of the typical work-related musculoskeletal symptoms of Korean workers. METHODS: We conducted this study using the data of the 5th Korean Working Conditions Survey (KWCS). As the subject of this study, 27,163 wage workers were selected, and classified into three groups according to occupational type (white-collar, service and sales, and blue-collar). In this study, job rotation means to change the work-related activities with other colleagues periodically and work-related LBP was defined as whether there was work-related LBP in the last 12 months. Chi-square test and logistic regression were used to analyze the relationship between job rotation and work-related LBP. RESULTS: Out of 27,163 workers, 2,421 (8.9%) answered that they had job rotation and 2,281 (8.4%) answered that they experienced work-related LBP. According to the results from logistic regression, job rotation was significantly associated with low prevalence of work-related LBP among blue-collar workers (odds ratio [OR]: 0.71, 95% confidence interval [CI]: 0.58-0.88), whereas no significant relationship was observed among white-collar, service and sales groups. In addition, the negative association between job rotation and work-related LBP among blue-collar workers was more pronounced when exposed to ergonomic risk factors (uncomfortable posture OR: 0.79, 95% CI: 0.64-0.98; heavy work OR: 0.74, 95% CI: 0.57-0.96; repetitive work OR: 0.74, 95% CI: 0.60-0.92). CONCLUSIONS: Job rotation was associated with low prevalence of work-related LBP among workers in the blue-collar occupational group in Korea. It is necessary to evaluate the effect of job rotation by occupational type and introduce an appropriate method of job rotation to reduce workers' work-related musculoskeletal symptoms.

Psychosocial factors affecting sleep quality of pre-employed firefighters: a cross-sectional study.

BACKGROUND: There have been no health-related studies of pre-employed firefighters without firefighter-specific job-related factors (FSJRF). This study aimed to evaluate the sleep quality of pre-employed firefighters and to examine the relationship between sleep quality and psychosocial factors. METHODS: We conducted a self-report questionnaire survey for 602 pre-employed firefighters at 3 Fire Service Academies after brief lecture about sleep. Sleep quality and psychosocial variables such as depression, anxiety, stress and social support were evaluated. The independent 2 sample t-test, χ2 test and multiple logistic regression analysis were used to evaluate the effect of the variables on the sleep quality of pre-employed firefighters. RESULTS: Among a total of 602 people, 347 (57.6%) had good sleep quality and 255 (42.4%) had poor sleep quality. Pittsburgh Sleep Quality Index score of them was 3.29 ± 1.41) and 7.87 ± 2.20), respectively. 24 (4.0%) were evaluated to have insomnia by Insomnia Severity Index. Logistic regression analyses showed that the depression (adjusted odds ratio [aOR]: 5.940, 95% confidence interval [CI]: 3.124-11.292), anxiety (aOR: 4.233, 95% CI: 2.138-8.381), stress (aOR: 2.880, 95% CI: 1.915-4.330) and social support (aOR: 0.959, 95% CI: 0.939-0.980) have a significant effect on sleep quality after adjusted by sex, age, smoking status, drinking status, caffeine intake, past shift working and circadian rhythm type. CONCLUSIONS: Depression, anxiety, stress and social support were associated with sleep quality among pre-employed firefighters. Repeated follow-up studies of pre-employed firefighters are needed to further assess their change of sleep quality and identify the FSJRF that may affect the sleep quality of firefighters.

Relationship between shift work and liver enzymes: a cross-sectional study based on the Korea National Health and Examination Survey (2007-2015).

BACKGROUND: Shift work has well-known adverse effects on health. However, few studies have investigated the relationship between shift work and hepatic disorders. This study aimed to evaluate the association between shift work and abnormal level of liver enzymes. METHODS: The aggregated data from the 2007-2009, 2010-2012, and 2013-2015 cycles of the Korea National Health and Nutrition Examination Survey was used for this study. The χ2 test and multiple logistic regression analysis were used to assess relationship between shift work and abnormal level of liver enzymes stratified by gender. RESULTS: The odds ratio (OR) of abnormal serum level of alanine aminotransferase (abnormal ALT) in female shift workers was higher with 1.31 (95% confidence interval: 1.00-1.71) compared with day workers after adjusting for covariates. After dividing into subgroups of the shift work pattern, the ORs of abnormal liver enzymes for each pattern compared with day work were not significantly higher. CONCLUSIONS: This study provides limited support for the hypothesis that shift work is related to liver enzyme abnormalities, but offers some evidence in favor of the idea that shift work affects female workers more than males on abnormal ALT. Further studies are needed to define the relationship between shift work and abnormal liver enzymes to be carried out as well as the gender difference in the association.

Relationship between simultaneous exposure to ergonomic risk factors and work-related lower back pain: a cross-sectional study based on the fourth Korean working conditions survey.

BACKGROUND: It is well known that ergonomic risk factors and back pain are related. However, few studies have examined the relationship between simultaneous exposure to these risk factors and back pain in a Korean population. We aimed to investigate the relationship between simultaneous exposure to ergonomic risk factors and work-related lower back pain (LBP) based on the fourth Korean Working Conditions Survey (KWCS). METHOD: The fourth KWCS (2014) was used for this study. Chi-square tests and logistic regression were used to assess relationship between 5 ergonomic risk factors and work-related LBP. We also analyzed the relationship between simultaneous exposure to 2 risk factors and work-related LBP. RESULTS: All 5 ergonomic risk factors (fatigue-inducing and painful posture; lifting or moving people; dragging, pushing, or moving heavy objects; standing posture; and repetitive hand or arm movements) were significantly correlated with work-related LBP in the severe exposure group (adjusted odd ratios [aOR] 5.09, 95% confidence interval [CI] 4.46-5.83; aOR 1.98, 95% CI 1.62-2.42; aOR 2.09, 95% CI 1.82-2.40; aOR 1.79, 95% CI 1.60-2.01; aOR 2.04, 95% CI 1.82-2.30, respectively). When exposed to 2 risk factors simultaneously, the relationship between exposure and work-related LBP was not greater than exposure to only 1 risk factor in our study (usually exposed to 'fatigue-inducing or painful posture' aOR 2.17, 95% CI 2.02-2.34; high exposure to both 'fatigue-inducing or painful posture' and 'dragging, pushing, or moving heavy objects' aOR 2.00, 95% CI 1.82-2.20). CONCLUSIONS: There was a strong relationship between severe exposure to each ergonomic risk factor and work-related LBP. However, when exposed to 2 ergonomic risk factors simultaneously, the relationship between exposure and work-related LBP was not stronger than when exposed to only 1 risk factor in our study.

Factors increasing the risk for psychosocial stress among Korean adults living in rural areas: using generalized estimating equations and mixed models.

BACKGROUND: This study was conducted to analyze the distribution of the psychosocial well-being index among adults living in two rural communities in Korea and to examine its correlation with lifestyle variables such as sleep duration, regular exercise, and sedentary time. METHODS: Using the cohort data of the Atherosclerosis Risk of a Rural Area Korean General Population, this study examined 3631 participants living in Wonju and Pyeongchang in Gangwon Province; their preliminary data were established from 2005 to 2007 while their follow-up data were collected 3 years later. This study investigated demographic characteristics, lifestyle habits, disease history, Psychosocial Well-being Index-Short Form (PWI-SF) scores, sleep duration, regular exercise, and sedentary time during work. Using repeated measures ANOVA, this study examined how the variables and PWI-SF scores changed over the course of 3 years and identified the correlation between them based on mixed model analysis. Afterwards, using the generalized estimation equation, this study identified each variable's risk towards the PWI-SF high-risk group and performed a stratified analysis by occupation after dividing the participants into farmers and non-farmers. RESULTS: The PWI-SF high-risk group was found to be 18.9% of the participants from preliminary data and 15.5% from follow-up data. The odds ratio towards the PWI-SF high-risk group was 1.503 (95% CI 1.241-1.821) in the short sleep duration group and 1.327 (95% CI 1.136-1.550) in the non-regular exercise group. A stratified analysis by occupation showed that middle and long sedentary time in the white-collar group increased the risk toward the PWI-SF high-risk group. CONCLUSIONS: Short sleep duration, no regular exercise, and long sedentary time in the white-collar group were identified as risk factors toward the PWI-SF high-risk group in the rural communities, and policy interventions are needed to address this issue.

Self-resilience as a protective factor against development of post-traumatic stress disorder symptoms in police officers.

BACKGROUND: This study was conducted to check whether self-resilience, one of the characteristics known to affect the occurrence of post-traumatic stress disorder (PTSD) symptoms after experiencing traumatic events, could serve as a protective factor for police officers whose occupational factors are corrected. METHODS: We conducted a cross-sectional study in which 112 male police officers in Gangwon Province participated. They visited the Wonju Severance Christian Hospital Occupational Environment Center for medical check-ups from June to December 2015. Their general characteristics were identified using structured questionnaires, and they were asked to fill in the Korean Occupational Stress Scale-Short Form (KOSS-SF). Further, the Center for Epidemiologic Studies-Depression Scale (CES-D), Connor-Davidson Resilience Scale-Korean (CD-RI-K), and Impact of Event Scale-Revised-Korean version (IES-R-K) were used to evaluate their job stress, depression, self-resilience, and PTSD symptoms. Logistic regression analysis was conducted to correct their personal, occupational, and psychological factors to analyze the relationship between self-resilience and PTSD symptoms. RESULTS: Among 112 respondents who experienced a traumatic event, those with low self-resilience had significantly higher rate of PTSD symptoms than those with high self-resilience even after correcting for the covariate of general, occupational, and psychological characteristics (odds ratio [OR] 3.51; 95 % CI: 1.06-19.23). CONCLUSIONS: Despite several limitations, these results suggest that a high degree of self-resilience may protect police officers from critical incident-related PTSD symptoms.

Representative levels of blood lead, mercury, and urinary cadmium in youth: Korean Environmental Health Survey in Children and Adolescents (KorEHS-C), 2012-2014.

BACKGROUND: This study examined levels of blood lead and mercury, and urinary cadmium, and associated sociodemographic factors in 3-18 year-old Korean children and adolescents. MATERIALS AND METHODS: We used the nationally representative Korean Environmental Health Survey in Children and Adolescents data for 2012-2014 and identified 2388 children and adolescents aged 3-18 years. The median and 95th percentile exposure biomarker levels with 95% confidence intervals (CIs) were calculated. Multivariate regression analyses were performed on log transformed exposure biomarker levels adjusted for age, sex, area, household income, and father's education level. The median exposure biomarker levels were compared with data from Germany, the US, and Canada, as well as the levels of Korean children measured at different times. RESULTS: The median levels of blood lead and mercury, as well as urinary cadmium were 1.23µg/dL, 1.80µg/L, and 0.40µg/L (95% CIs, 1.21-1.25, 1.77-1.83, and 0.39-0.41, respectively). The blood lead levels were significantly higher in boys and younger children (p<0.0001) and children with less educated fathers (p=0.004) after adjusting for covariates. Urinary cadmium level increased with age (p<0.0001). The median levels of blood mercury and urinary cadmium were much higher in Korean children and adolescents than those in their peers in Germany, the US, and Canada. Blood lead levels tended to decrease with increasing age and divergence between the sexes, particularly in the early teen years. Median levels of blood lead and urinary cadmium decreased since 2010. CONCLUSION: Sociodemographic factors, including age, sex, and father's education level were associated with environmental exposure to heavy metals in Korean children and adolescents. These biomonitoring data are valuable for ongoing surveillance of environmental exposure in this vulnerable population.

Association of current phthalate exposure with neurobehavioral development in a national sample.

BACKGROUND: Previous studies have indicated that phthalate exposure may influence the development of children, but the current data are limited, and controversy remains regarding the sex-specific and age-specific effects of phthalate exposure. METHODS: We investigated the sex- and age-specific associations of current phthalate exposure with neurobehavioral development scores in a nationally representative sample of 6-18-year-olds participating in the Korean Environmental Health Survey in Children and Adolescents (KorEHS-C). Neurobehavioral development was assessed using the Korean Child Behavior Checklist (CBCL, N=1723) and the Korean Attention Deficit Hyperactivity Disorder Rating Scale (ARS, N=867). We measured the concentrations of phthalate metabolites in urine samples using high-performance liquid chromatography tandem mass spectrometry. The associations between urine phthalate metabolite concentrations and neurobehavioral development were examined by survey regression analysis for complex sampling and penalized regression splines using a generalized additive model. RESULTS: Survey regression analysis revealed that a higher mono-n-butyl phthalate (MnBP) level was associated with social (ß=0.60; 95% confidence interval=0.15-1.05), thought (0.55; 0.08-1.03), and attention (0.68; 0.21-1.14) problems on the CBCL. A significant association was found between the MnBP level and the ARS hyperactivity subscale score (0.42; 0.05-0.58). Higher levels of MnBP (0.87; 0.20-1.54), mono-2-ethyl-5-oxohexyl phthalate (MEOHP, 0.61; 0.11-1.11) and mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP, 0.51; 0.04-0.97) were associated with an increase in thought problems among the girls. Among the younger children aged 6-11 years, significant positive associations between the MnBP (0.71; 0.09-1.33), MECPP (0.74, 0.14-1.34), MEOHP (0.65; 0.10-1.20), and MEHHP (0.71; 0.21-1.21) levels and social problems and between the MnBP (1.11; 0.37-1.84), MEOHP (0.64; 0.13-1.15), and MEHHP (0.66; 0.18-1.14) levels and attention problems were observed. The penalized regression splines for the age-specific relationships between the urinary MnBP, MEOHP, and MEHHP levels and social and attention problems exhibited positive supralinear relationships with downward curvature in the 6-11 year age group. In contrast, the score for social problems exhibited nearly linear relationships with these levels in the 12-18 year age group. CONCLUSIONS: In this national sample, increased phthalate exposure exhibited supralinear associations with social, thought and attention problems in children aged 6-11 years, who showed greater vulnerability to phthalate exposure. The results highlight the need for the environmental regulation of phthalate exposure in younger children, even at low dosages.

Association between night work and cardiovascular diseases: analysis of the 3rd Korean working conditions survey.

OBJECTIVES: This study was conducted to investigate the relationship between night work and cardiovascular diseases among wage workers in Korea. METHODS: The study was based on the 3rd Korean Working Conditions Survey (KWCS; 2011). This study included 29,711 wage workers. We used the chi-squared test and logistic regression to examine the association between cardiovascular diseases and night work and cumulative night work. RESULTS: Among all of the paid workers, 12.5% reported doing night work ≥ 1 day per month. Night work was significantly associated with an increased risk of cardiovascular diseases (odds ratio [OR] 1.58, 95% confidence interval [CI] 1.11-2.25). Also, compared to the group that did not do night works, the group with higher cumulative night work demonstrated an increased risk for cardiovascular diseases (OR 1.81, 95% CI 1.19-2.74). CONCLUSIONS: This study suggests that night work is significantly associated with cardiovascular diseases.

Association of active and passive smoking with occupational injury in manual workers: a cross-sectional study of the 2011 Korean working conditions survey.

This study was conducted to investigate the relationship of active and passive smoking with occupational injury among manual workers. Data from the 2011 Korean Working Conditions Survey were analyzed for 12,507 manual workers aged ≥15 yr. Overall, 60.4% of men and 5.8% of women were current smokers. The prevalence of injury was higher among never smokers who were exposed to secondhand smoke (SHS) (7.7% in men and 8.1% in women) than current smokers (4.2% in men and 4.1% in women). After controlling for potential confounders, in men, compared to those who never smoked and were not exposed to SHS, people who never smoked and were exposed to SHS (adjusted odds ratio (aOR)=3.7, 2.2-6.4) and current smokers (aOR=2.5, 1.6-3.8) were more likely to experience injury. Among women, the aORs of occupational injury were 8.4 (4.2-16.7) for never smoking women with occasional exposure to SHS and 3.5 (95% CI: 1.4-8.7) for current smokers, in comparison to never smoking women who were never exposed to SHS at work (reference group). The present study suggests that exposure to SHS is a possible risk factor of occupational injury for never smoking men and women.

The Relationship between Injury and Socioeconomic Status in Reference to the Fourth Korean National Health and Nutrition Examination Survey.

OBJECTIVES: This study aims to investigate the relationship between the total injury experience rate and socioeconomic status based on the fourth Korea National Health and Nutrition Examination Survey (KNHANES). METHODS: By analyzing data from the fourth KNHANES conducted from 2007 to 2009, we estimated the injury experience rate according to socioeconomic status, including the occupational characteristics of 11,837 subjects. Setting the injury experience rate as a dependent variable and socioeconomic status as an independent variable, we performed logistic regression to calculate odds ratios reflecting the likelihood of injury according to socioeconomic status while controlling for relevant covariates. RESULTS: In 797 subjects who had injury experience over the past 1 year, 290 persons (36.4%) had a work-related injury. As their income, home value, and educational status increased, their injury experiences decreased. Among occupational groups, the craft, equipment, machine operating, and assembling workers showed the highest rate (10.6%) of injury experience, and the lowest rate (5.7%) was found in the unemployed group. After adjusting for the confounding variables, the experience of injury was significantly related to several socioeconomic factors: high income (OR = 0.54; 95% CI: 0.34-0.86), high home value (OR = 0.65; 95% CI: 0.43-0.96), low education status (OR = 1.28; 95% CI: 1.07-1.52), and specific occupations such as craft, equipment, machine operating, and assembling work (OR = 1.99; 95% CI: 1.60-2.47), skilled agriculture, forestry and fishery work (OR = 1.43; 95% CI: 1.02-2.01), and simple labor (OR = 1.38; 95% CI: 1.04-1.82). CONCLUSIONS: The injury experience rate differed depending on the socioeconomic status. A negative correlation was found between the injury experience rate and income, low home value, and education level. Moreover, a higher rate of injury experience was found in occupation groups and physical worker groups in comparison to the unemployed group and white-collar worker groups. This study would be useful in selecting appropriate priorities for injury management in Korea.

Emotional labor and dysmenorrhea in women working in sales and call centers.

OBJECTIVES: This study was conducted to investigate the association between emotional labor and dysmenorrhea among women working in sales and call centers in Seoul, South Korea. METHODS: Working women in sales jobs and call centers in Seoul were interviewed face-to-face by well-trained interviewers. In total, 975 participants were analyzed in the final model. Emotional labor was measured using a constructed questionnaire with two components: an emotive effort component with three questions and an emotive dissonance component with five questions. To examine the association between emotional labor and dysmenorrhea, chi-squared tests and logistic regression were applied. RESULTS: The prevalence of dysmenorrhea among sales workers and call center workers were 43.0% and 61.1%, respectively. The adjusted odds ratios (OR) of emotive effort and emotive dissonance for dysmenorrhea in call center workers were 1.88 (95% confidence interval [CI], 1.07-3.28) and 1.72 (95% CI, 1.13-2.63), respectively. The adjusted OR of emotive effort and emotive dissonance for dysmenorrhea in sales workers were 1.71 (95% CI, 0.92-3.16) and 1.15 (95% CI, 0.67-1.98), respectively. CONCLUSIONS: Emotional labor was found to be associated with dysmenorrhea in call center workers. Further studies to investigate other factors, such as management strategies and the relationship between emotional labor and dysmenorrhea, are needed to support interventions to prevent dysmenorrhea that will further promote the quality of health and life of working women.

[Study on the relationship between childhood obesity and various determinants, including socioeconomic factors, in an urban area].

OBJECTIVES: This study was conducted to investigate the prevalence of childhood obesity, the association between the undesirable lifestyles and socioeconomic factors, the association between childhood obesity and various risk factors, including socioeconomic factors, and the agreement between the body mass index (BMI) classification and the body fat percentage. METHODS: The study subjects were all the 5th grade students from all the elementary schools in Gunpo City, Kyunggi Province, South Korea (4043 children at 22 schools). The subjects were measured for their height, weight and percent body fat etc. and they were also surveyed by questionnaire from March 18th to April 25th, 2005. To determine whether the children were within normal limits or not, standardized BMIs for each age group were used. The data was analyzed by logistic regression analysis using SAS 9.0 version. RESULTS: The prevalence of childhood obesity prevalence was 25.1%. Boys had a higher prevalence of obesity (27.5%) than did the girls (22.5%). Children had tendencies of having undesirable lifestyles and getting obese if they had a lower socioeconomic status. The risk factors for childhood obesity were low paternal education (OR: 1.17, 95% CI: 0.97-1.42) and non-parental caregivers (OR: 1.34, 95% CI: 0.98-1.82). Other risk factors for childhood obesity were a high birth-weight, longer TV/computer-using time, a lower fruit-eating frequency, short sleeping hours and parental obesity. The agreement rate between the BMI classification and the body fat percentage was 93.1%. CONCLUSIONS: This study showed the children had a higher prevalence of obesity: further, not only individual lifestyles, but also socioeconomic factors could influence childhood obesity. Childhood obesity was especially more problematic for children with a low socioeconomic status.