Risk of death from circulatory diseases in a cohort of patients exposed to chronic radiation

Abstract

To assess mortality from circulatory diseases (CD) in a cohort of workers exposed occupationally to chronic radiation in relation to external and internal exposure, by taking into account known non-radiation risk factors (RFs), such as smoking (including smoking index), alcohol consumption, hypertension, and body mass index. Mortality from CD (ICD-10: I00 - I99) was studied in a cohort of 22,377 nuclear power plant («Mayak» Production Association) workers exposed occupationally to chronic radiation. The study was based on the individual dose estimates of external and internal exposure taken from the new Mayak workers dosimetry system 2008 (MWDS-2008). The quantitative characteristics of smoking (smoking index) were used for the first time to assess the risk for CD in the cohort of workers exposed to chronic radiation. There was a statistically significant linear relationship between CD mortality and external gamma-dose after adjusting for the non-radiation RFs; the excess relative risk per unit dose (ERR/Gy) was 0.05 (95% confidence interval (CI): 0 to 0.11). Introducing an additional adjustment for internal alpha-dose resulted in a twofold increase in ERR/Gy=0.10 (95% CI: 0.02 to 0.21). There was a statistically significant increasing trend in CD mortality with the elevated absorbed dose from internal alpha-radiation in the liver (ERR/Gy=0.27; 95% CI: 0.12 to 0.48). However, ERR/Gy decreased and lost its statistical significance after adjusting for external gamma-dose. The results of this study are in good agreement with risk estimates obtained in the Japanese cohort of atomic bomb survivors and in the cohorts of occupationally exposed workers.