Risks of Circulatory Diseases among Korean Radiation Workers Exposed to Low-dose Radiation

High-dose radiation has been widely recognized as a risk factor for circulatory diseases. There is increasing evidence for risk of circulatory diseases in response to low and moderate radiation doses in recent years, but the results are not always consistent. We aimed to evaluate the associations between low-dose radiation exposure (<0.1 Gy) and the incidence of circulatory disease in a large cohort of Korean radiation workers. We collected data from a cohort of 187,001 radiation workers monitored for personal radiation dose since 1984 and linked with the National Health Insurance Service data from 2002 to 2021. Excess relative risks (ERRs) per 100 mGy were calculated to quantify the radiation dose-response relationship. The mean duration of follow-up was 13.3 years. A total of 12,705 cases of cerebrovascular disease (CeVD) and 19,647 cases of ischemic heart disease (IHD) were diagnosed during the follow-up period (2002-2021). The average cumulative heart dose was 4.10 mGy, ranging from 0 to 992.62 mGy. The ERR per 100 mGy with 10-year lagged cumulative heart doses was estimated at -0.094 (95% CI -0.248, 0.070) for CeVD and -0.173 (95% CI -0.299, -0.041) for IHD. The ERRs were not significantly changed after adjusting for confounding factors such as smoking, income, blood pressure, body mass index, and blood glucose level. A linear quadratic model was found to provide a better fit for the ERR of CeVD and IHD than a linear model (P = 0.009 and 0.030, respectively). There were no statistically significant variations in ERR/100 mGy estimates for either CeVD or IHD in terms of sex, attained age, and duration of employment; however, heterogeneity in the ERR/100 mGy estimates for CeVD among occupations was observed (P = 0.001). Our study did not find conclusive evidence supporting the association between occupational low-dose radiation and an increased risk of circulatory diseases. The significant negative ERR estimates for IHD need further investigation with a more extended follow-up period.