Risk of death from ischemic heart disease in the cohort of Chernobyl liquidators, nuclear energy employees

The article presents cohort study of risk of death from ischemic heart disease (IHD; ICD-10: I20-I25.9) in Chernobyl liquidators (clean-up workers), employees of nuclear energy. For the study the dataset of the Industry registry of persons exposed to radiation as the result of the Chernobyl accident was used. Chernobyl liquidators (12,663 males) included in the cohort study had worked inside the Chernobyl 30-km area from 1986 through 1990, the follow-up covered 20-year period (1995-2015). Some of them (1,327 men) previously were occupationally exposed to radiation and received additional radiation dose. Personal dosimetry and medical information used in the study included records on personal verified external radiation dose accumulated for the whole period of exposure inside the Exclusion 30-km zone around the Chernobyl NPP, occupationally exposed workers had additional, occupational, radiation dose accumulated for the whole period of their work with sources of ionizing radiation. Rough relative risk (ERR) of death from IHD was estimated in five dose groups formed on the basis of internal control. On the next stage of the study all data were stratified by age, radiation dose and follow-up period. To estimate excess relative risk of death from IHD with software package EPICURE (module AMFIT) data under study were grouped by age, with 10-year interval; the follow-up period (1995-2015) was divided on 5-year cycles, dose strata were formed. The relationship between dose and ERR value was examined. The study resulted in estimating radiation associated risk of death from ischemic heart disease. There is statistically reliable increase in death cases from IHD among Chernobyl liquidators per unit dose (ERR/Sv=0.7). The obtained results can be used in the development of radiation safety regulations for employees working with radioactive substances and those, who are chronically exposed to radiation. The uniqueness of the cohort of liquidators to obtain direct assessments of the risk of long-term effects of radiation exposure at low and intermediate doses indicates the need for further observation of this contingent. Further research suggests an increase in the statistical power of the analysis by increasing the observation period, as well as carrying out work aimed at reducing uncertainties in dose estimates and at improving the completeness and quality of epidemiological data.