Weekend work and depressive symptoms among Korean employees.

The purpose of this study was to quantify the association between weekend work and depressive symptoms in a representative sample of Korean employees. Subjects were 29 171 employees of companies in Korea. Data were obtained as part of the 2011 Korean Working Conditions Survey. Depressive symptoms were measured as a score of ≤7 on the World Health Organization Well-being Index. The association between weekend work and depressive symptoms was quantified using logistic regression, controlling for sociodemographic and work-related factors including the number of hours worked per week and stratified by gender. The prevalence of depressive symptoms was higher in employees who reported working at least one weekend day in the past month than in employees who reported working no weekend days in the past month. After controlling for confounders, including the number of hours worked per week, 1-4 days of weekend work in the past month (odds ratio [95% confidence interval] of 1.36 [1.18-1.57] in males and 1.32 [1.12-1.58] in females) and >4 days of weekend work in the past month (odds ratio [95% confidence interval] of 1.45 [1.19-1.78] in males and 1.36 [1.07-1.73] in females) were significantly associated with depressive symptoms. Weekend work was related with a significant increase in the prevalence of depressive symptoms in Korean workers.

Circadian Disruptions of Heart Rate Variability among Weekly Consecutive-12-hour 2 Shift Workers in the Automobile Factory in Korea.

OBJECTIVE: The objective of this study is to compare the circadian patterns of heart rate variability assessed by 24-hour ambulatory electrocardiographic (ECG) recordings during day shift and night shift among the workers in the 5 days-concecutive- 12-hour shift in an automobile factory in Korea. METHODS: The study population consisted 300 workers, who were randomly selected among the 8700 total workers in one car factory. To analyse circadian variation, the 24-hour ECG recordings (Marquette) were measured during day shift (08: 00-20: 00 h) and night shift (20: 00-08: 00 h). Analysis was performed for all time and frequency domain measures of HRV. 233 workers completed taking 24-hour ECG recordings. RESULTS: This study shows that the 24 hourcircadian variation mainly follows work/sleep cycle rather than day/night cycle among shift workers. This study also shows that among the night shift, the circadian variation between work and sleep cycle decreased compared to the work/sleep cycle among day shift workers. All time and frequency domain parameters (except LF/HF ratio) show significantly different between work and sleep in the day shift and night shift. CONCLUSIONS: These changes in heart rate variability circadian rhythms reflect significant reductions in cardiac parasympathetic activity with the most marked reduction in normal vagal activity among the shift workers. Especially, it suggests the circadian rhytm has blunted among the night workers. The quantification of the circadian variation in HRV can be a surrogates of workers' potential health risk, as well as suggests possible mechanisms through which the shift works compromise workers' health.