Annals of Occupational and Environmental Medicine

  • Volume 35
  • /
  • Pages.41.1-41.11
  • /
  • 2023
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  • 1225-3618(pISSN)
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  • 2052-4374(eISSN)
The Korean Society of Occupational & Environmental Medicine (대한직업환경의학회)
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Association between shift work and the risk of hypothyroidism in adult male workers in Korea: a cohort study

  • Seonghyeon Kwon (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Yesung Lee (Medical Support Division, Pyeongchang Country Public Health Clinic) ;
  • Eunhye Seo (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Daehoon Kim (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Jaehong Lee (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Youshik Jeong (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Jihoon Kim (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Jinsook Jeong (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine) ;
  • Woncheol Lee (Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine)
  • Received : 2023.07.17
  • Accepted : 2023.10.06
  • Published : 2023.12.31
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Abstract

Background: Shift work has been reported to have several harmful effects on the human body. However, a small number of studies have evaluated the association between shift work and adverse effects on the thyroid. In our longitudinal study, we examined the causal association between shift work and the risk of hypothyroidism. Methods: A Kangbuk Samsung Cohort Study was conducted on 112,648 men without thyroid disease at baseline who were followed up at least once between 2012 and 2019. Shift work status and shift schedule types were categorized using standardized questionnaires. Hypothyroidism was defined using the reference ranges of serum thyroid-stimulating hormones and free thyroxine levels. Hazard ratios (HRs) and 95% confidence intervals (CIs) for incident hypothyroidism were estimated using Cox proportional hazards regression analyses with the daytime work group as the reference. Results: During the 501,237 person-years of follow-up, there were 6,306 incident cases of hypothyroidism (incidence density, 1.26 per 100 person-years). The multivariable-adjusted HR of incident hypothyroidism for the shift work total group that included all shifts compared with the daytime work group was 1.27 (95% CI: 1.15-1.40). For the fixed evening, fixed night, rotating shift, and other shift workers, the multivariable-adjusted HRs (95% CI) were 1.11 (0.76-1.61), 2.18 (1.20-3.93), 1.39 (1.23-1.56), and 1.00 (0.82-1.22), respectively. In subgroup analyses by age, the association between shift work and hypothyroidism was more pronounced in younger participants (< 40 years; HR: 1.31; 95% CI: 1.16-1.47). Conclusions: Our large-scale cohort study showed an association between shift work and the incidence of hypothyroidism, especially in younger workers with night shifts.

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