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

Association between long working hours and metabolic dysfunction-associated steatotic liver disease: a nationwide population-based study in Korea

OBJECTIVES

Long working hour is a known risk factor for metabolic diseases. We explored the association between working hours and metabolic dysfunction-associated steatotic liver disease (MASLD).

STUDY DESIGN

Data on working hours among 22,818 workers (11,999 females) from the Korea National Health and Nutrition Examination Survey (2013-2021) were used for this study.

METHODS

MASLD was defined as a combination of hepatic steatosis combined with one or more of cardiometabolic risk factors (overweight/obesity, prediabetes/diabetes, raised blood pressure, hypertriglyceridemia, low high-density lipoprotein cholesterol). Hepatic steatosis was assessed using the hepatic steatosis index. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

The overall prevalence of MASLD was 30.4% in men and 18.1% in women. Among male workers, 20.2% worked ≥55 h/week, whereas among female workers, 10.1% worked ≥55 h/week. Compared with working 35-40 h/week, working ≥55 h/week was positively associated with overweight/obesity (OR: 1.21; 95% CI: 1.05-1.40), pre-diabetes mellitus (pre-DM)/DM (OR: 1.20; 95% CI: 1.04-1.38), raised blood pressure (OR: 1.17; 95% CI: 1.02-1.35), and presence of any cardiometabolic risk factors (OR: 1.56; 95% CI: 1.21-2.02). The adjusted OR (95% CI) of the association between working hours and MASLD was 1.27 (1.09-1.47) for ≥55 h/week compared with working 35-40 h/week in male workers. In female workers, long working hours were not clearly associated with cardiometabolic risk factors and MASLD.

CONCLUSION

Long working hours are positively associated with MASLD among Korean male workers. Policy interventions are needed to mitigate the adverse metabolic effects of prolonged working hours.

Relationship between long working hours and smoking behaviors: Evidence from population-based cohort studies in Korea

OBJECTIVES

Long working hours and overwork are growing public health concerns in the Western-Pacific region. We explored the relationship between working hours and smoking behaviors of Korean workers.

METHODS

This study included 284 782 observations (50 508 workers) from four nationwide cohort studies in Korea. Using generalized estimating equations, we estimated the associations of working hours with current smoking status, smoking initiation, and smoking cessation within each cohort. Cohort-specific estimates were combined through random-effect meta-analysis. Effect sizes were presented as odds ratios (OR) and 95 confidence intervals (CI).

RESULTS

The overall smoking prevalence was 26.8% within the cohorts. The adjusted OR (95% CI) of the association between working hours and current smoking were 1.01 (0.94-1.08) for <35 hours/week, 1.04 (1.01-1.09) for 41-48 hours/week, 1.06 (1.01-1.10) for 49-54 hours/week, and 1.07 (1.04-1.10) for ≥55 hours/week compared with 35-40 hours/week. The adjusted OR (95% CI) of the association between working hours and smoking cessation in the follow-up were 0.93 (0.85-1.02) for <35 hours/week, 0.89 (0.83-0.96) for 41-48 hours/week, 0.87 (0.81-0.95) for 48-54 hours/week, and 0.91 (0.85-0.98) for ≥55 hours/week compared with 35-40 hours/week. No clear associations were observed between working hours and smoking initiation.

CONCLUSION

Long working hours are associated with high current smoking risk and reduced likelihood of smoking cessation among Korean workers. Policy interventions are required to promote smoking cessation and reduce excess overwork for individuals experiencing long working hours.

Long working hours, work-life imbalance, and poor mental health: a cross-sectional mediation analysis based on the sixth Korean Working Conditions Survey, 2020-2021

Background There has been growing concern about the negative mental health impact of long working hours and overwork. Our study examined how work-life imbalance (WLI) could be a mediator between working hours and poor mental well-being.Methods We included 34,968 individuals from a nationwide cross-sectional survey in Korea. Self-reported working hours per week was collected, and mental health was assessed by the WHO-5 Well-Being Index. Counterfactual-based mediation models were employed to disentangle the total effects into a direct effect (work hour - poor mental health) and an indirect effect (work hour - WLI - poor mental health).Results Out of 34,968 participants, 52.6% worked 35-40 h/week, 20.0% worked 41-48 h/week, 11.7% worked 49-54 h/week, and 15.6% worked ≥55 h/week. The odds ratios (ORs) of the total impact of working hours on poor mental health were 1.08 (95% CI: 1.01-1.16) for 41-48 h/week, 1.28 (1.17-1.39) for 49-54 h/week, and 1.60 (1.48-1.74) for ≥55 h/week in comparison to 35-40 h/week. The ORs of the indirect effects were 1.04 (1.03-1.05) for 41-48 h/week, 1.08 (1.07-1.09) for 49-54 h/week, and 1.14 (1.12-1.16) for ≥55 h/week, accounting for 51%, 31%, and 28% of the total effects.Conclusion: Our findings suggest that WLI can partially mediate the association of long working hours with mental health deterioration. Policy efforts are required to mitigate the adverse mental health effects of overwork.

Association between long working hours and the development of suicidal ideation among female workers: An 8-year population-based study using the Korean Longitudinal Survey of Women & Family (2012-2020)

Long working hours and overwork have recently emerged as pressing public health concerns. We explored the association between long working hours and suicidal ideation in female workers. A total of 8017 women (24,331 observations) from the fourth to eighth waves of the Korean Longitudinal Survey of Women and Families (2012-2020) were analyzed. To address the repeated measurements within each participant, we employed a generalized estimating equation to estimate the odds ratio (OR) and 95% confidence intervals (CIs). The prevalence of suicidal ideation was 1.9% for those working 35-40 h/week and 4.4% for those working ≥55 h/week. Compared to individuals working 35-40 h/week, those working ≥55 h/week were more likely to experience concurrent suicidal ideation (OR [95% CI]:1.85 [1.43-2.39]). The OR (95% CI) of the association between long working hours and onset of suicidal ideation in the subsequent wave was 1.69 (1.20-2.38) for ≥55 h/week. In subgroup analysis, this association was pronounced among workers with low-income levels (OR [95% CI]: 1.97 [1.29-3.02]) and blue-collar occupations (OR [95% CI]: 2.27 [1.41-3.66]). Policy efforts are required to protect the mental health of female workers exposed to long working hours.

Association between long working hours and engagement in preventive healthcare services in Korean workers: Findings from the Korean National Health and Nutrition Examination Survey

BACKGROUND

Engagement in preventive healthcare services is crucial for preventing diseases. We explored how working hours are associated with engagement in preventive healthcare services, with a focus on gender differences.

METHODS

This cross-sectional study used data from the 2007-2012 Korean National Health and Nutrition Examination Survey. The dependent variable was engagement in each of the five preventive healthcare services (health check-ups, influenza vaccination, and stomach, breast, and cervical cancer screenings). We estimated the prevalence ratios (PRs) and 95% confidence intervals (CIs) using robust Poisson regression.

RESULTS

The study analyzed 19,819 workers (9119 women). The adjusted PRs (95% CI) of the association between working ≥55 h per week and engagement in preventive healthcare services among men were 0.95 (0.90-1.00) for health check-ups, 0.86 (0.77-0.96) for influenza vaccination, and 0.95 (0.87-1.03) for stomach cancer screening compared to working 35-40 h per week. Among women, the adjusted PRs (95% CI) of the association between working ≥55 h per week and engagement in preventive healthcare services were 0.84 (0.78-0.91) for health check-ups, 0.82 (0.73-0.92) for influenza vaccination, and 0.88 (0.80-0.97) for stomach, 0.85 (0.78-0.94) for breast, and 0.82 (0.74-0.91) for cervical cancer screenings.

CONCLUSION

Long working hours were negatively associated with engagement in preventive healthcare services, and the association was pronounced among female workers. Efforts to promote preventive healthcare participation among individuals with long working hours are necessary, and it is essential to consider the unique vulnerabilities of women when developing such policies.

Effect of long working hours on psychological distress among young workers in different types of occupation

BACKGROUND

We investigated how the association between long working hours and psychological distress varies across different employment and occupation types in young workers.

METHODS

Examining a nationally representative sample of 7246 Korean workers (3621 women) aged 15 to 40, we analyzed 23,492 observations spanning from 2016 to 2020. Psychological distress was measured using the Brief Encounter Psychosocial Instrument. We employed a generalized estimating equation to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Of the total observations, 5.2% worked <35 h/week, 52.9% worked 35-40 h/week, 23.5% worked 41-48 h/week, 10.3% worked 49-54 h/week, and 8.2% worked ≥55 h/week. The OR (95% CI) of the association between long working hours and psychological distress was 1.38 (1.11-1.72) for <35 h/week, 1.47 (1.32-1.65) for 41-48 h/week, 1.74 (1.49-2.04) for 49-54 h/week, and 2.11 (1.75-2.55) for ≥55 h/week compared to 35-40 h/week. The OR (95% CI) of the association between working ≥55 h/week and psychological distress was significantly higher among wage workers (OR [95% CI]: 2.37 [1.94-2.89]) compared to self-employed workers (OR [95% CI]: 0.84 [0.52-1.36]). Additionally, the OR (95% CI) of the association between working ≥55 h/week and psychological distress was significantly higher among white-collar workers (OR [95% CI]: 3.24 [2.54-4.13]) compared to service/sales workers (OR [95% CI]: 1.22 [0.86-1.72]) or blue-collar workers (OR [95% CI]: 1.71 [1.10-2.67]). No clear gender differences were observed.

CONCLUSION

Psychological distress caused by long working hours can be pronounced among white-collar and wage workers.

Association between long working hours and the onset of problematic alcohol use in young workers: A population-based longitudinal analysis in South Korea

BACKGROUND

Long working hours can negatively impact mental health. We examined the association between long working hours and problematic alcohol use among young Korean workers.

METHODS

We included a nationally representative sample of workers below the age of 40 from the Youth Panel between 2016 and 2020 (N = 7846; observations: 27,646). The exposure variable was working hours per week. Problematic alcohol use was assessed using the CAGE questionnaire, and generalized estimating equations were used to account for repeated measurements.

RESULTS

Observations of the participants revealed that 5 % worked < 35 h/week, 51 % worked 35-40 h/week, 24 % worked 41-48 h/week, 11 % worked 49-54 h/week, and 9 % worked ≥55 h/week. The prevalence of problematic alcohol use among the workers was 2 % for <35 h/week, 2 % for 35-40 h/week, 3 % for 41-48 h/week, 4 % for 49-54 h/week, and 4 % for ≥55 h/week. The adjusted odds ratios (95 % confidence intervals) for the association between working hours per week and the onset of problematic alcohol use in the following year were 0.86 (0.45-1.66) for <35 h, 1.56 (1.22-1.99) for 41-48 h, 2.03 (1.49-2.75) for 49-54 h, and 1.68 (1.17-2.42) for ≥55 h, compared to 35-40 h.

LIMITATIONS

The observational design of the study prevented the establishment of a causal relationship between working hours and the onset of problematic alcohol use.

CONCLUSION

Long working hours were associated with the development of problematic alcohol use. Policy interventions should promote healthier drinking habits among workers with long work hours.

Association between long working hours and cigarette smoking, leisure-time physical activity, and risky alcohol use: Findings from the Korea National Health and Nutrition Examination Survey (2014-2021)

BACKGROUND

Long working hours cause adverse health outcomes; however, the precise mechanisms underlying this relationship remain unknown. We examined the association between long working hours and health behaviors, as well as gender differences in this association.

METHODS

A nationally representative sample of 26,385 Korean workers was analyzed. The exposure variable was self-reported weekly working hours. The outcomes examined were cigarette smoking, high-level physical activity (defined as engaging in ≥150 min/week of moderate-to-vigorous leisure-time physical activity), and risky alcohol use (defined as consuming seven glasses for men or five glasses for women of alcohol in a single sitting, twice or more per week). Logistic regression models were utilized, and gender differences were examined by incorporating interaction terms into the regression models.

RESULTS

Among 26,385 workers, 4,109 (16%) worked ≥55 h/week. The prevalence of cigarette smoking, high-level physical activity, and risky alcohol use was 19%, 18%, and 14%, respectively. The odds ratio (OR) (95% confidence interval [CI]) of the association between working ≥55 h/week and outcomes was 1.26 (1.12-1.43) for cigarette smoking, 0.73 (0.65-0.83) for high-level physical activity, and 0.95 (0.83-1.08) for risky alcohol use compared to working 35-40 h/week. A moderating effect of gender on the association between long working hours and risky alcohol use was observed. The OR (95% CI) of the association between working ≥55 h/week was 0.88 (0.76-1.02) in men and 1.51 (1.12-2.05) in women.

CONCLUSION

Our findings emphasize the need for policy interventions aimed at reducing excessive working hours and fostering healthy lifestyle behaviors among individuals engaged in long working hours.