This study aimed to examine the impact of chronotype on depressive symptoms and explore the mediating effects of sleep quality, pre-sleep cognitive arousal, and social jetlag in a sample of wage earners.

A total of 3,917 waged workers were surveyed online in July 2022. Logistic regression and mediation analysis were used to assess the relationship between chronotype (morningness, intermediate, and eveningness) and depressive symptoms (Patient Health Questionnaire ≥ 5), and the mediating effects of Insomnia Severity Index (ISI), Pittsburgh Sleep Quality Index (PSQI), and Pre-Sleep Arousal Scale (PSAS). All analyses were adjusted for age, education level, income level, marital status, coffee consumption, alcohol consumption, physical activity, occupation, employment status, and working hours to calculate odds ratios (ORs).

The chronotypes of all the participants were divided into morningness (4.7%), intermediate (93.5%), and eveningness (1.8%). Multiple logistic regression analysis showed an increased risk of depression in the eveningness chronotype (OR: 2.96; 95% confidence interval [CI]: 1.51, 5.86). Regarding the mediation analysis, ISI mediated 28.44% (95% CI: 16.39–40.5), PSQI for 31.25% (95% CI: 19.36, 43.15), and PSAS-Cognitive Score (PSAS-C) for 23.58% (95% CI: 10.66, 36.50) of the association between chronotype and depressive symptoms. However, social jetlag did not significantly mediate this relationship. (percentage mediated = 0.75%, 95% CI: −3.88, 5.39)

Evening chronotypes exhibit an increased risk of depressive symptoms, which ISI, PSQI, and PSAS-C partially mediated. This suggests that interventions to improve sleep quality and maintain adequate sleep habits may effectively prevent and treat depression in employees with an eveningness chronotype.

In Korea, little research has focused on the relationship between discrimination in the workplace and sleep health. Thus, this study aims to investigate the association between such discriminatory experiences and insomnia, a common sleep disorder, using Korean employees’ data.

This study used data from the 6th Korea Working Conditions Survey. Discrimination experiences due to age, ethnic background, nationality, race, sex, religion, disability, sexual orientation, educational level, hometown, and employment status were investigated. The Minimal Insomnia Symptom Scale estimated insomnia symptoms. The association between discrimination experience and insomnia symptoms were analyzed using survey-weighted logistic regression analysis.

Based on experiences of discrimination over the past 12 months, insomnia symptoms were associated with discrimination experience due to religion (odds ratio [OR]: 3.70; 95% confidential interval [CI]: 1.58–8.69), sex (OR: 2.51; 95% CI: 1.87–3.37), age (OR: 2.30; 95% CI: 1.88–2.81), hometown (OR: 2.07; 95% CI: 1.44–2.97), employment status (OR: 1.69; 95% CI: 1.37–2.10), and educational level (OR: 1.67; 95% CI: 1.31–2.14). Furthermore, the prevalence of insomnia symptoms increased with the number of discrimination experiences.

In this study, discrimination experiences due to religion, sex, age, hometown, employment status, and educational level were significantly associated with insomnia symptoms. Furthermore, as the number of discrimination experiences increased, so did the prevalence of insomnia. Preventing workplace discrimination may improve workers’ sleep health.

In Korea, few studies clarify insomnia and its association and absenteeism or presenteeism. Therefore, this study aims to examine the association between insomnia and absenteeism/presenteeism using the sixth Korean Working Conditions Survey.

Insomnia was evaluated by the Minimal Insomnia Symptoms Scale (MISS). Absenteeism and presenteeism were assessed by asking if the employee had experienced absence or working despite being ill for the prior 12 months at the point of the survey. Multiple logistic analyses were conducted to explore insomnia and its association with absenteeism and presenteeism.

The odds ratios of insomnia for absenteeism and presenteeism were 3.48 (95% confidence interval [CI]: 2.76–4.39) and 3.68 (95% CI: 3.18–4.26) in the fully adjusted model. As the MISS scores increased, absenteeism and presenteeism showed the increasing trend that odd ratios increased accordingly from the first to the fourth quartile.

This study observed that insomnia was related to both absenteeism and presenteeism among Korean employees.

Occupational injury has been a serious social problem steadily. Sleep disturbance is a risk factor for occupational injury. However, there were few researches studied on the linking between sleep disturbance and occupational injury in general working population of Korea. Therefore, we explored the association between sleep disturbance and occupational injury among Korean workers.

This study used data from the 5th Korean Working Conditions Survey. Occupational injury was assessed by asking work related injury for 12 months prior to the point of the survey. Sleep disturbance was assessed using the Minimal Insomnia Symptoms Scale (MISS). To analyze the association between sleep disturbance and occupational injury, multiple logistic regression analysis was conducted.

The odds ratio (OR) of sleep disturbance group for occupational injury was 2.57 (95% confidence interval [CI]: 1.68–3.93) in the fully adjusted model. For the association between MISS score and occupational injury, it showed increasing trend that ORs increase from the 1st to the 4th quartiles. The OR of 2nd quartile was 1.10 (95% CI: 0.60–2.01), the OR of 3rd quartile was 2.27 (95% CI: 1.53–3.38) and the OR of 4th quartile was 2.80 (95% CI: 1.84–4.26).

Sleep disturbance was associated with occupational injury. In addition, increasing trend was observed between MISS score and occupational injury. These findings imply that developing of intervention programs to manage sleep disturbance and fatigue may be necessary to prevent occupational injury.

To investigate the risk of injury for indirect employment in Korea, we compared work environment, workplace exposure, and injury risk according to the type of employment contract between Korea and European Union (EU) countries.

We analyzed data of blue-collar workers from the fourth Korean Working Conditions Survey (2014) and the sixth European Working Conditions Survey (2015) and compared workplace risk factors and preventive factors for occupational injuries. Multiple logistic regression analysis was conducted to identify the relationship between occupational injury and the type of employment contract after adjusting for age and sex.

For descriptive characteristics, a relatively older age, lower income, lower proportion of full-time work, greater proportion in small-sized companies, and fewer unionizations were noted in indirect employment in Korea than in direct employment. Workplace exposure was significantly higher in indirect employment in both Korea and Europe. Among safety-related factors, indirect employment in both Korea and Europe lacked the support of company education, coworkers, and supervisors. Indirectly employed blue-collar workers had a significantly higher risk of occupational injury than those directly employed in Korea (odds ratio [OR]: 1.876), whereas there was no significant difference between directly and indirectly employed workers in EU countries (OR: 1.038).

Indirectly employed blue-collar workers have an increased risk of occupational injury in Korea.

The organizational justice model can evaluate job stressor from decision-making process, attitude of managerial or senior staff toward their junior workers, and unfair resource distribution. Stress from organizational injustice could be harmful to workers' mental health. The purpose of this study is to explore the association between organizational justice and depressive symptoms in a securities company.

To estimate organizational justice, a translated Moorman's organizational justice evaluation questionnaire (Korean) was employed. Cronbach's α coefficient was estimated to assess the internal consistency of the translated questionnaire. To assess depressive symptoms, the Center for Epidemiologic Studies Depression (CES-D) scale was used. The link between the sub-concepts of the organizational justice model and depressive symptoms was assessed utilizing multiple logistic regression models.

The risk of depressive symptoms was significantly higher among workers with higher levels of all subcategory of organizational injustice. In the full adjusted model odds ratio (OR) of higher level of procedural injustice 2.79 (95% confidence interval [CI], 1.58–4.90), OR of the higher level of relational injustice 4.25 (95% CI, 2.66–6.78), OR of higher level of distributional injustice 4.53 (95% CI, 2.63–7.83) respectively. Cronbach's α coefficient of the Korean version was 0.93 for procedural justice, 0.93 for relational justice, and 0.95 for distributive justice.

A higher level of organizational injustice was linked to higher prevalence of depressive symptoms among workers in a company of financial industry.