KSE
Articles
- Page Path
- HOME > Epidemiol Health > Volume 44; 2022 > Article
- Original Article Long working hours and the risk of hypothyroidism in healthy Korean workers: a cohort study
-
Yesung Lee1
, Woncheol Lee1
, Hyoung-Ryoul Kim2
-
Epidemiol Health 2022;44e2022104-0
DOI: https://doi.org/10.4178/epih.e2022104
Published online: November 8, 2022
- 1,010 Views
- 148 Download
- 0 Crossref
- 0 Scopus
2Department of Occupational and Environmental Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea
-
Corresponding author:
Hyoung-Ryoul Kim,
Email: cyclor@catholic.ac.kr
Abstract
OBJECTIVES
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.
METHODS
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.
RESULTS
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.
CONCLUSIONS
This large-scale cohort study demonstrated the association between long working hours and an increased risk of incident hypothyroidism with a dose-response relationship.
Cited
