Risk of Various Types of Cataracts in a Cohort of Mayak Workers Following Chronic Occupational Exposure to Ionizing Radiation

Abstract

Purpose: To assess cataract type specific risks in a cohort of workers occupationally exposed to ionizing radiation over prolonged periods. Material and methods: The present retrospective cohort study included 22,377 workers first employed at a nuclear production facility in 1948–1982 and followed up till the end of 2008. By the end of the follow-up period in the study worker cohort 3123 cases of cortical cataract, 1239 cases of posterior subcapsular cataract (PSC) and 2033 cases of nuclear cataracts were registered over 486,245, 489,162, 492,004 person-years of follow-up, respectively. Results: The incidence of PSC, cortical and nuclear cataracts was significantly linearly associated with the cumulative radiation dose. The excess relative risk per unit dose of external gamma-ray exposure (ERR/Sv) was 0.91 (95 % CI: 0.67–1.20) for PSC, 0.63 (95 % CI: 0.49–0.76) for cortical cataracts and 0.47 (95 % CI: 0.35–0.60) for nuclear cataracts. Exclusion of an adjustment for neutron dose and inclusion of additional adjustments for body mass index and smoking index reduced ERRs/Sv for all types of cataracts. However, an additional adjustment for glaucoma increased the incidence risks of cortical and nuclear cataracts just modestly (but not for PSC). Inclusion of an adjustment for diabetes mellitus reduced the ERR/Sv of external gamma-ray exposure only for PSC incidence. Increased incidence risks of all cataract types were observed in both males and females of the study cohort, but ERR/Sv was significantly higher in females (p < 0.001), especially for PSC. Conclusion: The incidence of various types of cataracts in the cohort of workers occupationally chronically exposed to ionizing radiation was associated with the cumulative dose of external gamma-ray exposure.