Analysis of the Influence of Radiation Exposure on Multimorbidity Among Liquidators of the Consequences of the Accident at the Chernobyl Nuclear Power Plant

Purpose: To give a general idea of the most common combinations of diseases in the male population of the Russian Federation and to identify the combinations of diseases, the development of which could be influenced by ionising radiation. Material and methods: Cohort study of the influence of external gamma irradiation on multimorbidity of the Chernobyl accident liquidation participants according to the data of the National Radiation Epidemiological Registry. Multimorbidity was defined as the presence in one participant of the cohort of two or more diseases from the list consisting of ten groups of diagnoses: diseases of lower respiratory tract, diseases of musculoskeletal system, diseases of endocrine system, mental disorders, oncology, neurology, diseases of digestive organs, diseases of cardiovascular system, diseases of genitourinary system, diseases of sense organs. The cohort consisted of men born between 1919 and 1969 who worked in the accident zone from 1986 to 1987 and had a documented whole-body external gamma dose. Cohort follow-up period: 1992–2021. The cohort size at the beginning of the follow-up was 59 290 people. The study participants were divided into two groups according to external gamma dose: up to 150 mGy – 34602 individuals, 150 mGy and more – 24 688 individuals. For all possible combinations of diagnoses, relative radiation risk was calculated as a measure of the association of exposure with diseases. The relative radiation risk was considered statistically significant if the left border of the one-sided 95 % confidence interval was greater than 1. Statistical analyses were performed using the R programming language for statistical computing and the R arules package. Results: During 30 years of follow-up, multimorbidity was noted in 62 % of individuals. The most common combinations of chronic diseases were combinations of cardiovascular diseases with digestive diseases (23 % of the original cohort), with lower respiratory diseases (22 %) and with musculoskeletal diseases (18 %). A combination of all four diagnosis groups was identified in 5 % of individuals. Nineteen multimorbid combinations with statistically significant relative radiation risk in the range (1.07–1.23) were identified. Conclusions: No effect of radiation exposure on the number of individuals with multimorbidity was found, but in the studied cohort there are individuals with cardiovascular diseases, endocrine diseases, oncology and combinations of these groups of diagnoses with diseases of other body systems may be caused by radiation exposure. The statistically significant relative radiation risk for combinations of diagnoses is, in general, greater than for the individual diseases that make up these combinations.