Micronucleus Abnormalities and Sex Differences in Medical Staff Exposed to Occupational Ionizing Radiation: A Retrospective Cohort Study

Gaiyan Du^1*Yuanling Wu¹Huiqin Zhang¹Zhenxin Guo¹Jingyi Wu¹Bozheng Zhang²Junyan Zhang¹Jing Wang¹Junkang Zhao¹Rui-Juan Zhang¹Ruonan Duan¹Fang Gao^1*

• ¹Shanxi Bethune Hospital, Shanxi Medical University, Taiyuan, China
• ²Emory University Emory College of Arts and Sciences, Atlanta, United States

Background: Long-term occupational exposure to low-dose ionizing radiation increases the risk of genetic damage among medical staff. Micronucleus (MN) frequency is a sensitive biomarker of chromosomal damage and genomic instability, but the influence of sex on MN responses to chronic radiation exposure remains insufficiently understood. Objective: This study aimed to assess sex – related differences between male and female healthcare workers in MN frequency abnormalities among those chronically exposed to ionizing radiation and to explore potential biological and occupational determinants underlying these differences. Methods: This retrospective cohort study included 102 medical staff (65 males, 37 females) from Shanxi Bethune Hospital, who had documented occupational radiation exposure for at least 10 years (2012–2024). According to the Chinese national standard, a micronucleus frequency of ≥6‰, that is, ≥6 micronuclei per 1,000 binucleated lymphocytes, was classified as abnormal, indicating elevated chromosomal damage. Poisson regression analysis was performed to examine predictors of MN abnormalities, adjusting for age, cumulative radiation dose, and occupational category. Results: Females had a significantly higher rate of MN frequency abnormalities than males (11.0 vs. 5.6 per 100 person-years, p = 0.008). In the multivariate Poisson regression analysis, female sex remained significantly associated with MN abnormalities (adjusted Coef. = 0.636, 95% CI: 0.176 – 1.096, p = 0.007). However, interpreting female sex as a strictly biological risk factor is limited by its correlation with occupational roles, most notably, the higher proportion of nurses among females. Furthermore, the absence of smoking and alcohol use data in the female subgroup complicates the assessment of behavioral confounding. In contrast, cumulative radiation dose during the study period was not significantly associated with MN abnormalities in the multivariate model (p > 0.05). Conclusion: After adjustment for measurable confounders, female healthcare workers exhibited significantly higher levels of cytogenetic damage. This association may reflect a combination of biological susceptibility, unmeasured occupational exposures, and behavioral factors—rather than cumulative physical radiation dose alone. These findings support including sex as a biological variable in occupational radiation safety protocols to improve risk stratification. They also highlight the need for future research to disentangle biological sex effects from correlated occupational and lifestyle determinants.