Risk of various types of cataracts in a cohort of Mayak workers following chronic occupational exposure to ionizing radiation

Abstract

This study is the first to report cataract type specific risks in a cohort of Russian Mayak Production Association workers following chronic occupational exposure to ionizing radiation. In this retrospective cohort study, 22,377 workers (females 25.4%) first employed in 1948-1982 were followed up till the end of 2008. All cataract subtypes were significantly dependent on sex, attained age, diabetes mellitus, myopia and glaucoma. For each of posterior subcapsular (PSC), cortical and nuclear cataracts, the risk of cataract incidence significantly linearly increased with increasing radiation dose. Excess relative risk per unit effective dose (ERR/Sv) from external γ-rays based on the linear model was 0.91 [95% confidence intervals (CIs) 0.67, 1.20] for PSC, 0.63 (95% CIs 0.49, 0.76) for cortical, and 0.47 (95% CIs 0.35, 0.60) for nuclear cataracts. For all three types of cataracts, exclusion of an adjustment for neutron dose as well as inclusion of additional adjustments for body mass index and smoking index decreased ERR/Sv of external γ-rays. Inclusion of an additional adjustment for glaucoma, however, modestly increased incidence risks for cortical and nuclear cataracts, but not PSC cataracts. Inclusion of an adjustment for diabetes mellitus decreased ERR/Sv of external γ-rays only for PSC incidence. Both males and females had increased risks for all three types of cataracts, but ERR/Sv was significantly higher in females than in males (p < 0.001), particularly for PSC cataracts. The results suggest that chronic occupational radiation exposure significantly increases risks of PSC, cortical and nuclear cataracts, and that such risks are higher in females than in males.

Keywords: Chronic ionizing radiation exposure; Cortical cataract; Gender difference; Mayak workers; Nuclear cataract; Posterior subcapsular cataract.