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.

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.

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.

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.

The risk of insomnia symptoms was highest in High Work-Family Conflict.

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.

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.

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.

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.

Owing to the coronavirus disease 2019 pandemic, being exposed to work from home and work during nonwork time simultaneously can lead to sleep disturbance; however, their combined effect is unclear. We aimed to investigate the combined effect of work from home and work during nonwork time on sleep disturbance.

This study used data from the Sixth Korean Working Condition Survey and included 27,473 paid workers. Logistic regression analysis was conducted to investigate the relationship between work from home, work during nonwork time, and sleep disturbance according to sex. We re-classified participants into 4 groups based on their working from home (No/Yes) and working during nonwork time (No/Yes). The relative excess risk due to interaction was calculated to examine the effect of exposure to both telecommuting and non-regular work hours on sleep disturbance.

Workers exposed to work from home and work during nonwork time had significantly higher risks of sleep disturbance for all, men, and women workers (OR [95% CI]: 1.71 [1.46–2.02], 1.79 [1.43–2.23], and 1.64 [1.29–2.08] for work from home and 3.04 [2.70–3.42], 3.61 [3.09–4.22], and 2.41 [2.01–2.90] for work during nonwork time, respectively). Compared to those who were not exposed to both factors, when workers had both job factors, the ORs (95% CI) of sleep disturbance for all, men, and women were 3.93 (2.80–5.53), 5.08 (3.21–8.03), and 2.91 (1.74–4.87), respectively. The relative excess risk due to interaction of work from home and work during nonwork time was not significant for sleep disturbance.

Work from home and work during nonwork time were each associated with sleep disturbance, but the interaction between the two factors on sleep disturbance was not observed in both men and women.

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.

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.

The aim of this study was to investigate the association between insomnia and hearing impairment among workers exposed to occupational noise.

This study included 809 male workers exposed to occupational noise. The participants underwent audiometric testing, and their insomnia was examined based on the Insomnia Severity Index test. Hearing impairment was defined as hearing threshold >25 dB hearing level in the range of 1–4 kHz.

According to analysis of covariance, it was observed that pure tone audiometry thresholds at 1–2 kHz in the right ear and at 1 kHz in the left ear were significantly higher among workers with insomnia compared to those with no insomnia. Multiple logistic regression analysis of insomnia for hearing impairments was performed, which showed the odds ratio was 1.806 (95% confidence intervals: 1.022–3.188, p = 0.042) after adjustment for age, working period, noise level, snoring, use of protection devices, diabetes mellitus, hypertension, smoking, alcohol consumption, regular exercise, waist circumference, total cholesterol, triglyceride and high density lipoprotein cholesterol.

Insomnia could be associated with hearing impairment in workers who are exposed to occupational noise. Additionally, insomnia may be associated with decreased hearing at low frequencies. Especially, more efforts are required to improve the quality of sleep for workers who are exposed to loud occupational noise. Further well- designed prospective studies are needed to clarify the relationship between insomnia and hearing impairment.

Aircraft noise is a major environmental noise problem. This study was conducted in order to investigate the relationship between sleep disturbance and exposure to aircraft noise on the residents who are living near an airport.

There were 3308 residents (1403 in the high exposure group, 1428 in the low exposure group, and 477 in the non-exposure group) selected as the subjects for this study. The Insomnia severity Index (ISI) and Epworth Sleepiness Scale (ESS) questionnaires were used to evaluate sleep disturbance.

The mean ISI and ESS scores were 6.9 ± 6.4 and 5.5 ± 3.7, respectively, and the average scores were significantly greater in the aircraft noise exposure group, as compared to the non-exposure group. The percentage of the abnormal subjects, which were classified according to the results of the ISI and ESS, was also significantly greater in the noise exposure group, as compared to the control group. The odd ratios for insomnia and daytime hypersomnia were approximately 3 times higher in the noise exposure group, as compared to the control group.

The prevalence of insomnia and daytime hypersomnia was higher in the aircraft noise exposure group, as compared to the control group. Further study is deemed necessary in order to clarify the causal relationship.