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Hyoung-Ryoul Kim 2 Articles
Long working hours and the risk of hypothyroidism in healthy Korean workers: a cohort study
Yesung Lee, Woncheol Lee, Hyoung-Ryoul Kim
Epidemiol Health. 2022;44:e2022104.   Published online November 8, 2022
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AbstractAbstract PDF
Long working hours have been reported to cause various health problems, but are currently practiced in many countries. Building upon a previous cross-sectional study, the authors aimed to elucidate the causal relationship between long working hours and hypothyroidism through a longitudinal study.
Data were collected at baseline from 45,259 participants without thyroid disease and with consistent weekly working hours (36-40, 41-52, 53-60, and >60 hours) during the follow-up period. Hypothyroidism was defined using the reference limits of serum thyroid-stimulating hormone and free thyroxine levels. By estimating hazard ratios (HRs) and 95% confidence intervals (CIs) using Cox proportional hazards regression analysis, the risk of incident hypothyroidism was evaluated with 36-40 hours of work per week as the reference.
During 138,261.7 person-years of follow-up, 2,914 participants developed hypothyroidism (incidence density, 2.11/102 person-years). The multivariable-adjusted HRs of incident hypothyroidism for 41-52 hours, 53-60 hours, and >60 hours of work per week were 1.13 (95% CI, 1.03 to 1.24), 2.53 (95% CI, 2.17 to 2.95), and 2.57 (95% CI, 2.09 to 3.15), respectively. In dose-response analyses, long working hours had an approximately linear relationship with hypothyroidism incidence. The risk of incident hypothyroidism in those who worked 53-60 hours and >60 hours per week compared with the reference group was significantly higher among the older age group (≥36 years, stratified by median age), men, and daytime workers.
This large-scale cohort study demonstrated the association between long working hours and an increased risk of incident hypothyroidism with a dose-response relationship.
Korean summary
Key Message
Association of Subway Driver's Depressive Symptoms and Experience of Work-Related Problems
Sun-Jin Jo, Hyeon Woo Yim, Hyoung-Ryoul Kim, Kang Sook Lee, Jong-Ik Park, Sung Man Chang
Epidemiol Health. 2010;32:e2010010.   Published online December 3, 2010
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  • 8 Citations
AbstractAbstract PDF

Subway drivers experience various types of work-related problems during their driving, and those experiences can act as risk factors for depressive symptoms. This study was conducted to investigate the association between work-related problems and subway driver's depressive symptoms.


We recruited all of the 961 current subway drivers of a subway company located in Seoul, South Korea and conducted a survey of their socio-demographic and vocational characteristics, hospital visits as an outpatient or inpatient, and work-related problem experiences during the last year. Work-related problems included an accident resulting in death or injury, a conflict with a customer, a sudden stop from an emergency bell, or a near accident. Depressive symptoms were measured with the Center for Epidemiologic Studies-Depression (CES-D) instrument. The survey was performed using a self-report questionnaire from April 16 to July 13, 2007. The data of 827 drivers (86.2%) were analyzed.


Experience of a conflict with a passenger (p=0.011), a sudden stop from an emergency bell (p=0.001), or a near accident (p=0.001) increased the prevalence of depressive symptoms among subway drivers. A multiple logistic regression analysis revealed that a sudden stop from an emergency bell increased the risk of depressive symptoms significantly (OR=2.59, p=0.026). Near accidents were marginally associated with a higher risk for depressive symptoms (OR=1.62, p=0.062).


The experience of a sudden stop from an emergency bell increased subway driver's depressive symptoms, and near accidents may increase the risk of depressive symptoms. Therefore, interventions for the drivers who had experienced these work-related problems are needed.

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Citations to this article as recorded by  
  • Research on the Evaluation Method of the Railroad Drivers’ Safety Psychology
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    Advances in Psychology.2022; 12(02): 352.     CrossRef
  • Relationships of social support, coping styles, perceived stress, and quality of life: The difference between metro drivers and station attendants in Xi’an, China
    Bo Liu, Xiaoyang Xin, Quan Xu, Yue Han, Ying Li, Xuqun You
    Current Psychology.2022;[Epub]     CrossRef
  • Posttraumatic stress reactions of underground drivers after suicides by jumping to arriving trains; feasibility of an early stepped care outpatient intervention
    Giancarlo Giupponi, Heike Thoma, Dorian Lamis, Alberto Forte, Maurizio Pompili, Hans-Peter Kapfhammer
    Journal of Trauma & Dissociation.2019; 20(5): 495.     CrossRef
  • Factors associated with suicide ideation among subway drivers in Korea
    Junsu Byun, Hyoung-Ryoul Kim, Hye-Eun Lee, Se-Eun Kim, Jongin Lee
    Annals of Occupational and Environmental Medicine.2016;[Epub]     CrossRef
  • Sickness absence of LU train drivers after track incidents
    S. Chavda
    Occupational Medicine.2016; 66(7): 571.     CrossRef
  • Systematic Review of the Impact of Suicides and Other Critical Incidents on Railway Personnel
    Cécile Bardon, Brian L. Mishara
    Suicide and Life-Threatening Behavior.2015; 45(6): 720.     CrossRef
  • The association between psychiatric disorders and work-related problems among subway drivers in Korea
    Se-eun Kim, Hyoung-Ryoul Kim, Jong-Ik Park, Hae Woo Lee, Jongin Lee, Junsu Byun, Hyeon Woo Yim
    Annals of Occupational and Environmental Medicine.2014;[Epub]     CrossRef
  • Comments on Jo and Colleagues' Paper (2010) "Association of Subway Driver's Depressive Symptoms and Experience of Work-Related Problems"
    Jae-Min Kim
    Epidemiology and Health.2011; 33: e2011002.     CrossRef

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