Non-regular workers are steadily increasing on account of improving corporate productivity. They are classified as non-permanent, part-time, or non-typical workers. Non-regular work has a negative impact on workers' physical and mental health. This study analyzed the relationship between non-permanent, part-time and non-typical work and insomnia among Korean wage workers, and investigated the differences and interactions between different work patterns.

The Fifth Korean Working Conditions Survey was used in this study. Non-regular work patterns were classified into 7 types: type 1, sole non-permanent; type 2, sole part-time; type 3, sole non-typical; type 4, part-time-non-typical; type 5, non-permanent-non-typical; type 6, non-permanent-part-time; type 7, all inclusive. Insomnia was measured on a scale from “normal sleep” to “insomnia” based on the 3-item Minimal Insomnia Symptom Scale. Multiple logistic regression was used to analyze the association between non-regular work patterns and insomnia among wage workers.

After multivariate adjustment, a significantly increased odds ratio (OR) for insomnia was found in types 1, 2, 3, 4, 5, 6, and 7 of non-regular work patterns compared to regular work patterns. After stratification for shift and night work, the OR of the group with shift and night work was higher than that of the group without shift and night work.

Insomnia was significantly associated with non-regular work patterns. This association was prominent in workers with shifts and night work. This finding suggests that proper work patterns may be needed to reduce the risk of insomnia among Korean wage workers and workers who initially had insomnia should consider these results before placement.

This study was conducted to determine the association between work-life (WL) balance, effort-reward (ER) imbalance, and depressive mood in Korean wage workers when 2 models were considered simultaneously.

We analyzed 26,014 Korean workers including 13,471 men and 12,543 women from the 4th Korean Working Conditions Survey data. Multiple logistic regression was used to analyze the association between WL, ER status, and the depressive mood of Korean workers. We classified the subjects into a total of 4 groups as follows. Group 1: WL and ER status are both “balanced”, group 2: WL status is “imbalanced” and ER status is “balanced”, group 3: WL status is “balanced” and the ER status is “imbalanced”, group 4: WL and ER status are both “imbalanced.”

We found significantly increased odds ratios (ORs) for depressive mood in groups 2, 3, and 4 compared with group 1 after adjusting for the general and occupational characteristics of the subjects in both men and women. We also found that the trend of ORs increased gradually from groups 2 to 4 compared with group 1 in both men and women; group 2: OR: 1.23 (95% confidence interval [CI]: 1.12–1.35), group 3: OR: 1.40 (95% CI: 1.27–1.55), group 4: OR: 1.99 (95% CI: 1.74–2.28) compared with group 1 in men; group 2: OR: 1.28 (95% CI: 1.15–1.42), group 3: OR: 1.45 (95% CI: 1.31–1.59), group 4: OR: 2.04 (95% CI: 1.76–2.36) compared with group 1 in women.

As a result, we found the association between imbalanced WL, ER status, and depressive mood in Korean workers using 2 models simultaneously. It is important to provide a balanced WL and ER condition to improve the mental health of workers.

Workers spend most of their social lives at work and have relationships of varying nature with people in the workplace. Direct supervisors, in particular, have a direct and lasting impact on workers, which may influence workers' mental health. Depression is very prevalent worldwide, and social concern about the disease is on the rise. The aim of this study is to investigate the effect of direct supervisors' behavior on the depressive mood of Korean wage workers.

We used data from the 4th Korean Working Conditions Survey held in 2014; 22,212 participants were included in the analysis. The quality of a direct supervisor's behavior was categorized from 0 (= lowest) to 5 (= highest) points. The degree of depressive mood was measured on a scale from “normal mood” to “likely depression” based on the 5-item World Health Organization Well-Being Index (WHO-5) questionnaire. Multiple logistic regression was used to analyze the association between the quality of the direct supervisor's behavior and the depressive mood of wage workers.

After multivariable adjustment, significantly increased odds ratio (OR) for likely depression was found in the 4, 3, 2, 1, and 0 points of the quality of the direct supervisor's behavior compared to 5 points. After stratification for the level of satisfaction with working conditions, the OR of the unsatisfied groups was higher than that of the satisfied groups.

Likely depression was found to be significantly associated with a low quality of direct supervisor's behavior. This association was stronger in workers who were not satisfied with their working conditions. This study suggests that proper management of the direct supervisor's behavior is needed to reduce the risk of depression among Korean wage workers.