Epidemiology and Health

Systematic Review

Confounding and the healthy worker survivor effect in studies of medical radiation workers: a systematic review of methodological approaches: Eun Jung Park, Kyoungyeol Yuk, Jaeho Jeong, Won Jin Lee; Epidemiol Health. 2026;48:e2026009. Published online February 4, 2026; DOI: https://doi.org/10.4178/epih.e2026009

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Abstract

Confounding and the healthy worker survivor effect (HWSE) represent major methodological challenges in epidemiology, particularly in studies of low-dose exposures, where effect sizes are small and risk estimates can be readily distorted by bias. This systematic review aimed to summarize the methods used to adjust for confounding and the HWSE in studies of medical radiation workers. We systematically searched PubMed and Embase for studies of medical radiation workers from inception through June 30, 2025. Studies reporting excess risk estimates for any health outcomes associated with occupational radiation exposure were included. Study selection followed the PECO (Population, Exposure, Comparator, Outcome) criteria, and data were synthesized descriptively. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in PROSPERO (CRD42024589851). Sixteen eligible studies from 3 countries were identified, all of which were rated as high quality. To control for confounding, regression was used in all studies, followed by stratification (62.5%) and restriction (18.8%). Age, sex, and birth year were adjusted for in all models, with smoking being the next most frequently controlled variable. To mitigate the HWSE, only a single approach, adjustment for employment characteristics, was identified, and it was applied in 3 studies (18.8%). No other approaches, including restriction or g-methods, were employed. Although confounding is generally addressed using conventional analytical approaches, the HWSE has rarely been considered in studies of medical radiation workers. More comprehensive strategies that explicitly account for the HWSE are needed to improve the validity of risk estimates, particularly in low-dose occupational studies.

Summary

Korean summary
교란 및 건강근로자 생존효과는 역학 연구에서 해결해야 할 중요한 과제이며, 특히 저노출 연구에서는 효과 크기가 상대적으로 작아 이러한 영향에 더욱 취약하다. 연구 결과, 의료방사선종사자 연구에서 교란은 회귀분석 및 층화와 같은 전통적인 방법을 통해 적절히 보정되고 있지만, 건강근로자 생존효과를 줄이기 위한 방법은 대부분의 연구에서 적용되지 않고 있다. 향후 역학 연구에서는 보다 정확한 위험도 평가를 위해 건강근로자 생존효과를 줄이기 위한 다양한 방법의 적용이 필요하다.

Key Message
Confounding and the healthy worker survivor effect (HWSE) are major methodological challenges in epidemiology, particu- larly in studies involving low-dose exposure. Although confounding is generally considered to have only a limited impact in occupational epidemiology, a variety of analytical methods have nonetheless been applied to control it. In contrast, the HWSE, despite being widely recognized as a major source of bias, has rarely been mitigated in practice. More comprehensive strat- egies that explicitly account for the HWSE are needed to improve the validity of risk estimates.

Citations

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Cardiovascular composite events and the healthy worker effect among noise-exposed workers: a retrospective cohort study
Jiahui Liu, Qi Li, Jiamin Liu
Frontiers in Public Health.2026;[Epub] CrossRef

Cohort Profile

Cohort study profile: a cohort of Korean atomic bomb survivors and their offspring: Hamin Lee, Jin-Wu Nam, Mi Kyung Kim, Inah Kim, Yu-Mi Kim, Boyoung Park; Epidemiol Health. 2024;46:e2024089. Published online November 18, 2024; DOI: https://doi.org/10.4178/epih.e2024089

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Abstract

The Korean Atomic Bomb Survivor Cohort (K-ABC) study was designed to investigate the health impacts of atomic bomb exposure on Korean survivors and to explore whether these effects are passed down genetically to their descendants. This paper outlines the study’s design, data collection methods, baseline socio-demographic characteristics, exposure status, and disease prevalence among the participants, based on survey responses and health examinations. From 2020 to 2024, a total of 2,544 individuals, comprising 1,109 atomic bomb survivors (G1), 1,193 children of G1 (G2), and 242 grandchildren of G1 (G3), consented to participate in the study. Of these, 1,828 participants (659 in G1, 927 in G2, and 242 in G3) completed the survey and underwent health examinations, representing a participation rate of 71.9%. Exposure information was gathered using a questionnaire and verified through records from the Korean Red Cross and a handbook issued by the Japanese government. Disease prevalence was determined based on participants’ self-reported physician diagnoses. This study presents details about the K-ABC study and provides baseline data on the participants recruited. These data will be valuable for interpreting the results of future K-ABC studies.

Summary

Korean summary
한국인 원폭피해자 코호트 연구는 1945년 일본에서 원자폭탄에 피폭된 원폭 피해자 1세와 이들의 자녀인 2세, 3세의 건강과 질병 위험도을 장기적으로 조사한다. 이를 위해 2020년부터 2023년까지 설문조사를 통해 정보를 수집하였고, 이후 설문조사와 함께 건강보험공단, 국립암센터, 통계청 등 공공 기관에서 보유하고 있는 데이터를 연계하여 추적관찰을 수행해 나갈 예정이다.

Key Message
The Korean atomic bomb survivor’s cohort study investigates the long-term health and disease risks of first generation atomic bomb survivors exposed in Japan in 1945, as well as their second generation and third generations. From 2020 to 2023, information was collected through surveys. Follow-up will be conducted through surveys and secondary data linkage from public institutions such as the National Health Insurance Service, the Korea Central Cancer Registry, and Statistics Korea.

Citations

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Inherited Trauma Across Generations: The Lived Experiences of Korean Second-Generation Atomic Bomb Survivors
Youngsub Yoon, Sihyun Park
Qualitative Health Research.2026;[Epub] CrossRef
Assessment of Health Status in Populations Living in the Semipalatinsk Nuclear Test Site Region: Results of Screening
Altay Dyussupov, Galiya Alibayeva, Dariya Shabdarbayeva, Lyudmila Pivina, Nailya Chaizhunussova, Andrey Orekhov, Meruyert Massabayeva, Assel Baibussinova, Alexandra Lipikhina, Zhanargul Smailova, Gulnara Batenova, Saulesh Apbassova, Murat Lepesbayev, Saul
Healthcare.2026; 14(13): 1988. CrossRef
Validation of self-reported cancer diagnoses in the Korean Atomic Bomb Survivor Cohort study
Hamin Lee, Jin-Wu Nam, Mi Kyung Kim, Inah Kim, Yu-Mi Kim, Boyoung Park
Cancer Epidemiology.2025; 97: 102817. CrossRef

Editorial

Lessons from radiation epidemiology: Won Jin Lee; Epidemiol Health. 2018;40:e2018057. Published online November 14, 2018; DOI: https://doi.org/10.4178/epih.e2018057

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Abstract

Radiation epidemiology has developed as a specialized field and has unique characteristics compared to the other fields of epidemiology. Radiation exposure assessment is highly quantified and health risk assessment can yield precise risks per unit dose in each organ. At the same time, radiation epidemiology also emphasizes the uncertainty of the estimated doses and risks. More radiation epidemiologists work in radiation societies rather than those of epidemiology. This specialization deepens the research of radiation studies but also results in fragmentation from general epidemiology. In addition to continued involvement with radiation-related sciences, therefore, more efforts to communicate with the other fields of epidemiology are necessary for radiation epidemiology.

Summary

Korean summary
방사선 역학은 역학의 세부 전공분야로서 다른 역학 분야와 구별되는 특성들이 있다. 노출 및 건강영향 평가에서의 정량화된 접근방법을 비롯하여 방사선 역학의 많은 장점들은 다른 역학분야에서도 응용될 필요가 있다. 이러한 전문화는 역학 연구의 내용을 깊게 발전시키는데 큰 역할을 하고 있는 반면, 일반 역학 분야와 분열되는 단점도 있다. 따라서 기존 방사선 관련 학문들과의 지속적인 교류뿐 아니라 다른 역학분야와의 활발한 교류를 통해 방사선 역학 및 전체 역학분야를 발전시키는 것이 중요하다.

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The influence of revised ordinance on radiation protection management in Japanese hospitals: device deployment and involvement of radiology technologists
Arman Nessipkhan, Naoki Matsuda, Noboru Takamura, Noboru Oriuchi, Hiroshi Ito, Kazuo Awai, Takashi Kudo
Japanese Journal of Radiology.2025; 43(1): 117. CrossRef
The activation mode of a dirty-bomb can modify the health risk estimation profile
Rocco Pascale Neto, Vitor W. L. Silva, William H. S. Profeta, Andrew Collinson, Ricardo M. Stenders, Rodrigo C. Curzio, Hélio C. Vital, Edson R. Andrade
International Journal of Radiation Biology.2025; 101(2): 215. CrossRef
Testing and results of an open-source radiation epidemiology model using the Goiânia accident
Riccardo Quaranta, Gian Marco Ludovici, Luca Romano, Guglielmo Manenti, Andrea Malizia
The European Physical Journal Plus.2024;[Epub] CrossRef
A rapid radiation epidemiology tool for the analysis of the propagation of radiation following a radiological dispersal device explosion
Riccardo Quaranta, Gian Marco Ludovici, Luca Romano, Guglielmo Manenti, Andrea Malizia
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On the use of free code tools to simulate the propagation of radiation following dirty bomb explosions in sensible contexts
Riccardo Quaranta, Gian Marco Ludovici, Guglielmo Manenti, Pasqualino Gaudio, Andrea Malizia, A. Lyoussi, F. D’Errico, M. Carette, M. Joyce, R. Hodák, I. Jenčič, P. Le Dû, M. Morichi, S. Pospíšil, C. Reynard-Carette, L. Snoj, L. Vermeeren
EPJ Web of Conferences.2023; 288: 06009. CrossRef
The expression profile of redox genes in human monocytes exposed in vitro to γ radiation
Gina Manda, Cristian Postolache, Ionela Victoria Neagoe, Andreea Csolti, Elena Milanesi, Maria Dobre
Radiation Physics and Chemistry.2020; 170: 108634. CrossRef

Original Articles

Physician’s awareness of lung cancer screening and its related medical radiation exposure in Korea: Seri Hong, Suyeon Kim, Mina Suh, Boyoung Park, Kui Son Choi, Jae Kwan Jun; Epidemiol Health. 2018;40:e2018002. Published online January 20, 2018; DOI: https://doi.org/10.4178/epih.e2018002

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Abstract

OBJECTIVES
Through a survey on perception of lung cancer screening and accompanying medical radiation exposure in Korea, the present study was to investigate its current situations and evaluate various perception of physicians regarding it in order to propose measures for improvements.

METHODS

Medical specialists in national cancer screening institutions selected through stratified random sampling were subjected to face-to-face interview using a structured questionnaire. We investigated physicians’ perception on effectiveness of lung cancer screening depending on screening modality, selection criteria for subjects of screening, types of equipment used to screen, and perception for seriousness of adverse effects following the test. In addition, odds ratios to underestimate risk of radiation exposure from screening were calculated through logistic regression analysis.

RESULTS

Each response that chest X-ray is effective for lung cancer screening and that smoking history is not considered prior to screening recommendation accounted for more than 60% of respondents, suggesting the chance of unnecessary screening tests. Regarding adverse effects of lung cancer screening, about 85% of respondents replied that false positive, radiation exposure, and overdiagnosis could be ignored. About 70% of respondents underestimated radiation dose from lung cancer screening, and a low proportion of physicians informed patients of radiation exposure risk.

CONCLUSIONS

It was found that most physicians underestimated harms of lung cancer screening including radiation exposure and were lack of awareness regarding lung cancer screening. It should be noted that physicians need to have proper perceptions about screening recommendation and accompanying possible harms, for successful implementation of the screening program.

Summary

Korean summary
전국 100여개 국가암검진 기관을 대상으로 폐암검진 관련 설문을 수행한 결과, 효과적인 폐암검진의 수단이나 방법에 대한 이해 및 검사에 수반되는 각종 부작용에 대한 의사들의 인식이 확연히 부족한 것으로 조사되었다. 그 중에서도 특히 의료방사선 노출에 대한 낮은 인지도는, 촬영 시 피폭량에 대한 전반적인 과소평가 및 방사선 노출 위험과 관련한 환자 교육의 부재를 통해 확인할 수 있었다. 인구집단 대상 선별검사의 도입에 따른 잠재적인 위해 가능성과 그 결과에 대한 고민은 반드시 필요하며, 이와 관련된 의료제공자들의 인식 개선을 촉구하는 본 연구는 정책 도입에 앞서 선결되어야 할 과제로서 공중보건학적 측면에서 중요한 의의를 지닌다.

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Assessment of radiation knowledge and awareness among radiology staff in tertiary hospitals: a study in Wuxi, China
J. Yuan, D. Liu, J. Ni
Radioprotection.2024; 59(3): 184. CrossRef
Why is the screening rate in lung cancer still low? A seven-country analysis of the factors affecting adoption
Charlotte Poon, Tim Wilsdon, Iqra Sarwar, Alexander Roediger, Megan Yuan
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Correlation Study on Clinical Laboratory Findings with Occupational Exposure to Low Dose Ionizing Radiation in Nuclear Workers in Korea.: Young Khi Lim, Keun Young Yoo; Korean J Epidemiol. 2001;23(2):8-18.

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Abstract PDF: Abstract
PURPOSE
Even though atomic energy and radioisotope had been made for a peaceful purpose, some of the public do't feel safe possibly due to potential exposure to ionizing radiation. While health effects of high level radiation are almost deterministic, the stochastic effects of the 'low-dose radiation' have not come to a correct conclusion. This correlation study was conducted to assess the health effect due to potential exposure th low-dose radiation in the nuclear power plants workers in Korea.
METHODS
The study subjects was selected among the nuclear workers. Among those who attend the epidemiologic survey for screening of any malignancies done by the study group of Seoul National University Hospital during 1992-1993, 1) those who had undertaken both the physical examination with clinical laboratory tests and the direct interview with questionnaire, 2) male workers, and 3) those with record on radiation dosimetry as well as employment records in the company. Correlation analysis with Pearson's correlation coefficients and quantitative analysis with normal ranges of various tests were done by the PC-SAS for window.
RESULTS
Total cumulative radiation doses was relatively low, ranging 1 mSv at the lowest to 391 mSv at the highest. Moreover, mostly 68.7% of the subjects was within lower limit of total cumulative doses under 10 mSv. Among the clinical laboratory test, statistical significant correlation was see in hemoglobin(HGB), creatinine(CRE), and carcinoembryonic antigen(CEA).
CONCLUSION
This study concluded that health effect of occupational exposure to low-dose ionizing radiation is minimal or, if any, extremely lower than expected in the nuclear power plants workers in Korea. Major limitation of this study is that the healthy worker effect could not excluded. A large-scale prospective epidemiologic study on the relationship between radiation exposure and health hazard is needed to draw a more valid conclusion.; Summary

A Study on Patterns of Dose for Radiation Workers in Korea.: Soo Yong Choi, Tae Hwan Kim, Cha Kwon Chung, Chul Koo Cho; Korean J Epidemiol. 1999;21(1):72-80.

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Abstract PDF: Abstract
This study presents data on the externally received doses for radiation workers who used the Korea Radioisotope Association's personal monitoring and dose record keeping service from 1984. Distributions of annual dose by age of worker and occupational category were given. The number of radiation workers registered was 23,257 in 1997. The trend of the number of radiation workers and their annual doses increased since 1984. The measured radiation dose were generally low. The collective annual dose and the mean annual dose were 33.45 Sv and 1.44 mSv, respectively. Very few workers(0.5%) exceeded 20 mSv(2 rem) and only 1 exceeded 50 mSv, the legal limit for dose.; Summary

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