Women's Employment in Industries and Risk of Preeclampsia and Gestational Diabetes: A National Population Study of Republic of Korea.

Background: Some working conditions may pose a higher physical or psychological demand to pregnant women leading to increased risks of pregnancy complications. Objectives: We assessed the association of woman's employment status and the industrial classification with obstetric complications. Methods: We conducted a national population study using the National Health Information Service database of Republic of Korea. Our analysis encompassed 1,316,310 women who experienced first-order live births in 2010-2019. We collected data on the employment status and the industrial classification of women, as well as their diagnoses of preeclampsia (PE) and gestational diabetes mellitus (GDM) classified as A1 (well controlled by diet) or A2 (requiring medication). We calculated odds ratios (aORs) of complications per employment, and each industrial classification was adjusted for individual risk factors. Results: Most (64.7%) were in employment during pregnancy. Manufacturing (16.4%) and the health and social (16.2%) work represented the most prevalent industries. The health and social work exhibited a higher risk of PE (aOR = 1.11, 95% confidence interval [CI]: 1.03-1.21), while the manufacturing industry demonstrated a higher risk of class A2 GDM (1.20, 95% CI: 1.03-1.41) than financial intermediation. When analyzing both classes of GDM, women who worked in public administration and defense/social security showed higher risk of class A1 GDM (1.04, 95% CI: 1.01, 1.07). When comparing high-risk industries with nonemployment, the health and social work showed a comparable risk of PE (1.02, 95% CI: 0.97, 1.07). Conclusion: Employment was associated with overall lower risks of obstetric complications. Health and social service work can counteract the healthy worker effect in relation to PE. This highlights the importance of further elucidating specific occupational risk factors within the high-risk industries.

Associations of chronotype and insomnia with menstrual problems in newly employed nurses at university hospitals in the Republic of Korea.

Background: Dysmenorrhea and menstrual cycle changes occur in women working shifts. Circadian rhythm disruption and sleep disturbances associated with shift work leads to health problems. We identified chronotypes and the occurrence of insomnia among newly employed university hospital nurses and investigated the association of these factors with menstrual problems. Methods: We conducted pre-placement health examinations for shift workers using self-reported questionnaires between 2018 and 2020. A total of 463 nurses were included in the study. Sociodemographic data, shift work experience, and information on insomnia were collected from health examination data. In addition, details regarding chronotype, dysmenorrhea, irregular and abnormal menstrual cycles, amenorrhea, and contraceptive use were obtained from the questionnaire. Multiple logistic regression analysis was performed to study the association between chronotype, insomnia, and menstrual problems after controlling for age, body mass index, contraceptive use, amenorrhea, and prior shift work. Results: The prevalence rates of dysmenorrhea, irregular menstrual cycles, and longer menstrual cycles were 23.8%, 14.9%, and 4.1%, respectively. The risk of dysmenorrhea increased in the evening-type (odds ratio [OR]: 3.209; 95% confidence interval [CI]: 1.685-6.113) and those with insomnia (OR: 1.871; 95% CI: 1.074-3.261). Additionally, the risk of an irregular menstrual cycle (OR: 2.698; 95% CI: 1.167-6.237) increased in the evening-type, and the risk of a longer menstrual cycle (OR: 4.008; 95% CI: 1.354-11.864) increased in individuals with insomnia. Conclusions: Our findings suggest that dysmenorrhea is promoted in the evening-type and insomnia individuals. There may be an increased risk of irregular menstrual cycles among evening-type nurses and an increased risk of longer menstrual cycles among those with insomnia. Therefore, factors such as evening-type and insomnia should be considered for the prevention of menstrual problems in women performing shift work.

Does the father's job matter? Parental occupation and preterm birth in Korea.

OBJECTIVES: Limited evidence is available regarding the impact of paternal occupation and its combined effect with maternal occupation on preterm birth. Therefore, we assessed the association of maternal and paternal occupations with preterm birth. METHODS: We used the national birth data of Korea between 2010 and 2020. Parental occupations were divided into 5 categories: (1) managers; (2) professionals, technicians, and related workers; (3) clerks and support workers; (4) service and sales workers; and (5) manual workers. A multinomial logistic regression model was used to calculate the adjusted odds ratios (aORs) of extremely, very, and moderate-to-late preterm births per occupational category considering individual risk factors. RESULTS: For the 4,004,976 singleton births, 40.2% of mothers and 95.5% of fathers were employed. Compared to non-employment, employment was associated with a lower risk of preterm birth. Among employed mothers, service and sales occupations were associated with a higher risk of preterm birth than managerial occupations (aOR, 1.06; 95% confidence interval [CI], 1.01 to 1.10 for moderate-to-late preterm births). The father's manual occupation was associated with a higher risk of preterm birth (aOR, 1.09; 95% CI, 1.05 to 1.13 for moderate-to-late preterm) than managerial occupations. When both parents had high-risk occupations, the risk of preterm birth was higher than in cases where only the mother or neither of the parents had a high-risk occupation. CONCLUSIONS: Paternal occupation was associated with preterm birth regardless of maternal employment and occupation and modified the effect of maternal occupation. Detailed occupational environment data are needed to identify the paternal exposures that increase the risk.

Risk of adverse pregnancy outcomes by maternal occupational status: A national population-based study in South Korea.

OBJECTIVE: This study examined the association between maternal occupational status and adverse pregnancy outcomes in the general South Korean population. METHODS: We analyzed 1 825 845 employed and non-employed women with a diagnostic code for pregnancy in the National Health Insurance Service (NHIS) database (2010-2019) of South Korea. Based on their employment status and type of occupation, we calculated risk ratios for three adverse outcomes: early abortive outcomes (miscarriage, ectopic pregnancy, and molar pregnancy), stillbirth, and no live birth (diagnosis of pregnancy with no record of live birth thereafter, which include early abortive outcomes and stillbirth) with adjusting for covariates. RESULTS: Overall, 18.0%, 0.7%, and 39.8% ended in early abortive outcomes, stillbirths, and no live births, respectively. The risk of early abortive outcomes and stillbirths was higher in non-employed women than in employed women, while no live births were more frequent in employed women. Those in the health and social work industry showed the highest risk of no live births. Manufacturing jobs (1.030, 95% CI: 1.013, 1.047) and health/social work (1.029, 95% CI: 1.012, 1.046) were associated with an increased risk of early abortive outcomes compared with financial and insurance jobs. Consistently higher risks of no live births were observed in the manufacturing, wholesale/retail trade, education, health/social work, and public/social/personal service occupation. CONCLUSION: Employment during pregnancy and several occupation types were associated with a higher risk of pregnancy loss. Additional research using detailed job activity data is needed to determine specific occupational causes of adverse pregnancy outcomes.

Relationship between chronotype and depressive symptoms among newly hired hospital nurses in the Republic of Korea.

Background: This study was conducted to examine the relationship between chronotype and depressive symptoms to provide grounded knowledge in establishing nurses' health promotion strategies. Methods: The subjects of this study were 493 newly hired nurses working in 2 general hospitals within the university from September 2018 to September 2020. Sociodemographic and work-related characteristics were collected from a medical examination database and a self-reported questionnaire. These included sex, age, marital status, living situation, education level, alcohol consumption, physical activity, prior work experience before 3 months, workplace, and departments. To analyze the associations between the chronotype and depressive symptoms, multiple logistic regression analyses were performed to calculate odds ratios (ORs). Results: Among participants, 9.1% had depressive symptoms and 16.4% had insomnia. The subjects are divided into morningness (30.2%), intermediate (48.7%), and eveningness (21.1%). The multiple logistic regression analysis controlling for age, living status, education level, alcohol consumption, physical activity, workplace, prior work experience before 3 months, and insomnia, revealed that the OR of depressive symptoms in the eveningness group was 3.71 (95% confidence interval [CI]: 1.50-9.18) compared to the morningness group, and the R2 value was 0.151. It also can be confirmed that insomnia symptoms have a statistically significant effect on depressive symptoms (OR: 2.16, 95% CI: 1.03-4.52). Conclusions: Our findings suggest that evening-type nurses are more likely to have depression than morning-type nurses. We should consider interventions in a high-risk group such as the evening type nurses to reduce depressive symptoms in nurses.

Social distancing attitudes, national context, and health outcomes during the COVID-19 pandemic: Findings from a global survey.

This study analyzes global health consequences of the new coronavirus disease by focusing on the roles of normative beliefs on social distancing and country-level factors, i.e., mobility estimate and globalization index. We fitted mixed effects models to examine the associations between two outcome measures, depression and self-rated health, and their multilevel determinants using a subset of Global Behaviors and Perceptions in the COVID-19 Pandemic, an online survey consisting of more than 100,000 participants from 67 nations. Results show that both personal beliefs and general beliefs significantly predict depression and poor health. There is also a contextual effect of globalization on depression. In addition, the relationship between general beliefs and depression is stronger in countries with lower rates of mobility. With respect to poor health, the effect of general beliefs similarly varies inversely with the level of globalization. Our study indicates that one's own beliefs and the perception of others' regarding social distancing, along with contextual factors (measures of mobility and globalization), critically shape mental and physical health. Subjective and objective factors should be considered, in other words, in properly understanding the differential impact of COVID-19 across the world.

The Change of Self-Rated Health According to Working Hours for Two Years by Gender.

OBJECTIVE: The aim of this study was to confirm the association between working hours and self-rated health, and to find the degree of changes in health level by working hours according to gender. METHODS: This study was based on the 929 workers (571 men and 358 women) from the Korean Labor and Income Panel Study during 2004⁻2006. To minimize the healthy worker effects, the study subjects included only those who did not have any chronic diseases, and who answered their health status as "moderate" or above in the baseline. Logistic regression analysis was used to confirm the associations between working hours and self-rated health. RESULTS: In men, working hours per week of 47⁻52 h, 53⁻68 h, and >68 h were associated with 1.2, 1.3, and 1.1 times increases, respectively, in the odds ratio on worsened self-rated health, compared with the reference group (40⁻46 h). On the other hand, the risks were 1.0, 2.2, and 2.6 times increases in women. However, the results were different according to gender in the group with less than 40 h. The men with less than 40 h had a 0.9 times odds ratio on worsened self-rated health. For the women with less than 40 h, the odds ratio on self-rated health was 5.4 times higher than the reference group. CONCLUSIONS: Working more than 52 h per week had a negative effect on health, regardless of gender. However, in the group with less than 40 h, the negative association between working hours and self-rated health were shown only in women. Health outcomes due to working hours may differ by gender. Therefore, further studies are needed to explore the causes of these results.

Working hours and depressive symptoms: the role of job stress factors.

BACKGROUND: South Korea is one of the countries with the longest working hours in the OECD countries. The aim of this study was to evaluate the effect of working hours on depressive symptoms and the role of job stress factors between the two variables among employees in South Korea. METHODS: This study used data from the Korea Working Conditions Survey in 2014. Study subjects included 23,197 employees aged 19 years or older who work more than 35 h per week. Working hours were categorized into 35-39, 40, 41-52, 53-68, and more than 68 h per week. Depressive symptoms were assessed using the WHO's Well-Being Index with a cut-off score of 13. We calculated prevalence ratios of depressive symptoms according to working hours using log-binomial regression. Through the percentage change in prevalence ratios, we identified the extent of the role of job stress factors that explain depressive symptoms. RESULTS: The risks of depressive symptoms were significantly higher in people who worked 35-39 h per week (PR: 1.09, CI: 1.01-1.18), 53-68 h/week (PR: 1.21, CI: 1.16-1.25), and more than 68 h/week (PR: 1.14, CI: 1.07-1.21) than 40 h/week, after adjusting for confounding variables. Job stress explained the effects of long working hours on depressive symptoms in about 20-40% of the groups working more than 40 h/week. Among the factors of job stress, social support was 10-30%, which showed the highest explanatory power in all working hours. Reward explained 15-30% in the more than 52 h working group, and reward was the most important factor in the working group that exceeded 68 h. CONCLUSIONS: We showed the working hours could be an independent risk factor for depressive symptoms in employees. To improve workers' mental health, it is important to strengthen social support in the workplace, to provide adequate rewards as they work, and ultimately to regulate the appropriate amount of working hours.

Toxic Effects of Methanol among Illegally Dispatched Workers at Aluminum CNC Cutting Process in Small-Scale, Third-Tier Subcontractor Factories of Smartphone Manufacturers in the Republic of Korea.

An outbreak of occupational methanol poisoning occurred in small-scale, third-tier factories of large-scale smartphone manufacturers in the Republic of Korea in 2016. To investigate the working environment and the health effects of methanol exposure among co-workers in the methanol poisoning cases, we performed a cross-sectional study on 155 workers at five aluminum Computerized Numerical Control (CNC) cutting factories. Gas chromatography measured air and urinary methanol concentration. In the medical examination, symptom surveys, ophthalmological examinations, and neurobehavioral tests were done. Multiple logistic regression analyses controlling for age and sex were conducted to reveal the association of employment duration with symptoms. Air concentrations of methanol in factory A and E ranged from 228.5 to 2220.0 ppm. Mean urinary methanol concentrations of the workers in each factory were from 3.5 mg/L up to 91.2 mg/L. The odds ratios for symptoms of deteriorating vision and central nervous system (CNS) increased according to the employment duration after adjusting for age and sex. Four cases with an injured optic nerve and two cases with decreased neurobehavioral function were founded among co-workers of the victims. This study showed that the methanol exposure under poor environmental control not only produces eye and CNS symptoms but also affects neurobehavioral function and the optic nerve. The role of subcontracting production and dispatched work under poor environmental control was discussed.

Air pollution exposure during pregnancy and ultrasound and birth measures of fetal growth: A prospective cohort study in Korea.

Few studies have examined the effects of air pollution on fetal growth based on ultrasound measures during pregnancy. More data is needed to evaluate the windows of special vulnerability. Our aim was to investigate the association of ambient air pollution during pregnancy with fetal and neonatal characteristics in a cohort of Korean women. Maternal exposure to particulate matter with an aerodynamic diameter<10µm (PM10) and nitrogen dioxide (NO2) was estimated using land-use regression models based on residential address. The biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) were evaluated via ultrasonography, and birth weight (BW), birth length (BL), and head circumference at birth (BHC) were obtained from medical records. The multiple linear regression model was used to adjust for confounders, and the mixed-effect model was used to evaluate longitudinal effect. The negative effects for NO2 and PM10 were estimated; in the adjusted analyses the decreases of BPD were -0.26mm (95% confidence interval [CI]=-0.41 to -0.11, with a 10µg/m3 increase) in the second trimester for NO2, and -0.30mm (95% CI=-0.59 to -0.03, with a 10µg/m3 increase) in the third trimester for PM10. Both NO2 and PM10 levels (10µg/m3) during third trimester were inversely associated with BHC, and NO2 level was inversely associated with BL in all exposure windows. No significant associations for AC, FL, and EFW were observed. The longitudinal analyses showed inverse association of NO2 exposure with head and length growth (P<0.001). Our findings suggest that ambient air pollution is associated with impaired fetal head size from mid-gestation onwards.

Associations of Shift Work and Its Duration with Work-Related Injury among Electronics Factory Workers in South Korea.

This study aimed to explore the association between shift work and work-related injuries. We collected data on workers from an electronics factory. This cross-sectional study included 13,610 subjects, who were assessed based on a self-reported questionnaire about their shift work experiences, work-related injuries, and other covariates. Multiple logistic regression models were used to evaluate the associations between shift work and work-related injuries and were estimated using the odds ratio. We found that the current and past shift workers, compared to non-shift workers, were associated with a 2.7- and 1.7-fold higher risk of work-related injury. There was a dose-response relationship between shift work duration and work-related injury among current female shift workers. Shift work increased the risk of work-related injuries, and the impact could be different depending on gender.

Associations of prenatal and early childhood mercury exposure with autistic behaviors at 5years of age: The Mothers and Children's Environmental Health (MOCEH) study.

BACKGROUND: Although mercury is an established neurotoxin, only few longitudinal studies have investigated the association between prenatal and early childhood mercury exposure and autistic behaviors. METHODS: We conducted a longitudinal cohort study using an ongoing prospective birth cohort initiated in 2006, wherein blood mercury levels were measured at early and late pregnancy; in cord blood; and at 2 and 3years of age. We analyzed 458 mother-child pairs. Autistic behaviors were assessed using the Social Responsiveness Scale (SRS) at 5years of age. Both continuous SRS T-scores and T-scores dichotomized by a score of ≥60 or <60 were used as outcomes. RESULTS: The geometric mean of mercury concentrations in cord blood was 5.52µg/L. In adjusted models, a doubling of blood mercury levels at late pregnancy (ß=1.84, 95% confidence interval [CI]: 0.39, 3.29), in cord blood (ß=2.24, 95% CI: 0.22, 4.27), and at 2years (ß=2.12, 95% CI: 0.54, 3.70) and 3years (ß=2.80, 95% CI: 0.89, 4.72) of age was positively associated with the SRS T-scores. When the SRS T-scores were dichotomized, we observed positive associations with mercury levels at late pregnancy (relative risk [RR]=1.31, 95% CI: 1.08, 1.60) and in cord blood (RR=1.28, 95% CI: 1.01, 1.63). CONCLUSION: We found that blood mercury levels at late pregnancy and early childhood were associated with more autistic behaviors in children at 5years of age. Further study on the long-term effects of mercury exposure is recommended.

Neurological Complications Resulting from Non-Oral Occupational Methanol Poisoning.

Methanol poisoning results in neurological complications including visual disturbances, bilateral putaminal hemorrhagic necrosis, parkinsonism, cerebral edema, coma, or seizures. Almost all reported cases of methanol poisoning are caused by oral ingestion of methanol. However, recently there was an outbreak of methanol poisoning via non-oral exposure that resulted in severe neurological complications to a few workers at industrial sites in Korea. We present 3 patients who had severe neurological complications resulting from non-oral occupational methanol poisoning. Even though initial metabolic acidosis and mental changes were improved with hemodialysis, all of the 3 patients presented optic atrophy and ataxia or parkinsonism as neurological complications resulting from methanol poisoning. In order to manage it adequately, as well as to prevent it, physicians should recognize that methanol poisoning by non-oral exposure can cause neurologic complications.

Two cases of methyl alcohol intoxication by sub-chronic inhalation and dermal exposure during aluminum CNC cutting in a small-sized subcontracted factory.

BACKGROUND: Methyl alcohol poisoning has been mainly reported in community. Two cases of methyl alcohol poisoning occurred in a small-sized subcontracted factory which manufactured smartphone parts in Korea. CASE PRESENTATION: One young female patient presented with dyspnea and visual disturbance. Another young male patient presented with visual disturbance and myalgia. They treated with sodium bicarbonate infusion and hemodialysis for metabolic acidosis. In addition, he received ethyl alcohol per oral treatment. Her and his urinary methyl alcohol concentration was detected as 7.632 mg/L, 46.8 mg/L, respectively, although they were treated hemodialysis. Results of the working environment measurement showed that the concentration of methyl alcohol (1030.1-2220.5 ppm) in the air exceeded the time weighted average (200 ppm). They were diagnosed with optic neuropathy due to methyl alcohol poisoning and still have visual impairment. CONCLUSIONS: Workers who hired as dispatched employees in a small-sized subcontracted factory were exposed to high concentrations of methyl alcohol. The workplace had poor ventilation system. In addition, workers did not wear proper personal protect equipment. Working environment measurement and annual chekups for workers were not performed. They were in a blind spot to occupational safety and health. More attention is needed to protect vulnerable workers' health.