Epidemiology and Health

Original Article

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; DOI: https://doi.org/10.4178/epih.e2022104

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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.

Summary

Korean summary
대규모 코호트연구를 통해 장시간노동을 수행한 노동자들에서 갑상선기능저하증의 위험이 높아지는 것을 확인할 수 있었다. 특히 연령, 성, 교대근무 유무에 따라 층화하여 분석한 결과에서 고연령, 남성, 교대근무를 하지 않는 노동자에서 관련성의 크기가 증가하였다.

Key Message
This large-scale cohort study (The Kangbuk Samsung Health Study), which used 45,259 participants without thyroid disease at baseline and estimated hazard ratios (HRs) using Cox proportional hazards regression analysis, demonstrated the association between long working hours and an increased risk of incident hypothyroidism with a dose-response relationship especially in older age group, men, and daytime workers.

Citations

Citations to this article as recorded by

Association between shift work and the risk of hypothyroidism in adult male workers in Korea: a cohort study
Seonghyeon Kwon, Yesung Lee, Eunhye Seo, Daehoon Kim, Jaehong Lee, Youshik Jeong, Jihoon Kim, Jinsook Jeong, Woncheol Lee
Annals of Occupational and Environmental Medicine.2023;[Epub] CrossRef

MERS-Epidemiologic Investigation

Epidemiological investigation of the 119th confirmed Middle East Respiratory Syndrome coronavirus case with an indefinite mode of transmission during the Pyeongtaek outbreak in Korea: Jong Hyuk Choi, Byoungin Yoo, Soon Young Lee, Eun Gyu Lee, Moran Ki, Woncheol Lee, Jong Rak Jung, Kyujin Chang; Epidemiol Health. 2015;37:e2015054. Published online December 10, 2015; DOI: https://doi.org/10.4178/epih/e2015054

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Abstract Summary PDF Supplementary Material

Abstract

Since the first case was diagnosed on May 20, 2015, there were 186 confirmed cases of Middle East Respiratory Syndrome (MERS) until the end of outbreak in South Korea. Although medical institutions were the most identifiable sources of MERS transmission in South Korea, similar to other countries, in-depth epidemiological investigation was required for some confirmed cases with indefinite contact history or hospital visit records. The subject of epidemiological investigation in the present study was a 35 year-old male patient diagnosed with MERS (#119) who lived in Asan-city and worked in Pyeongtaek-city. Various potential sources of transmission were carefully investigated. While he could have been exposed to MERS through a friend from Saudi Arabia or confirmed MERS cases in his workplace, neighboring areas, and medical institutions, as well as contacts in his home, the chances of transmission were low; however, the potential for transmission through his local community could not be excluded. Practically, it was difficult to determine the modes of transmission for all outbreak cases in communicable disease that occurred in this short period of time. The investigation to identify the mode of transmission in this case was ultimately unsuccessful. However, the various data collected and analyzed to reveal modes of transmission provided detailed information that could not be collected using only interview surveys.

Summary

Korean summary
2015년 한국에서 유행한 메르스 환자들 중, 감염 경로가 불분명한 119번째 환자에 대한 심층 역학조사를 통해 다양한 감염경로의 가능성을 검토하였다. 감염경로를 명확하게 밝혀내지 못한 한계점이 있지만, 지역사회 전파에 대한 가능성을 제시하였다. 감염병 대유행시 효율적인 감염경로 파악을 위해서는 다방면의 자료에 대한 확보체계와 이를 신속히 분석하고 판단할 수 있는 전문 인력 확충이 필요하다.

Citations

Citations to this article as recorded by

A database of geopositioned Middle East Respiratory Syndrome Coronavirus occurrences
Rebecca E. Ramshaw, Ian D. Letourneau, Amy Y. Hong, Julia Hon, Julia D. Morgan, Joshua C. P. Osborne, Shreya Shirude, Maria D. Van Kerkhove, Simon I. Hay, David M. Pigott
Scientific Data.2019;[Epub] CrossRef

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