Risk Assessment of Senile Cataract Incidence in a Cohort of Nuclear Workers of Mayak Production Association

Purpose: To estimate incidence risk for senile cataracts in a cohort of workers employed at nuclear production facility, that were occupationally exposed to radiation taking into account non-radiation risk factors. Material and methods: Senile cataract incidence (cataracts) is studied in the cohort of Mayak PA workers first employed at one of the main facilities (reactors, radiochemical or plutonium production plants) during 1948–1982 (22,377 individuals). All members of the study cohort were occupationally exposed to gamma-rays or neutrons over a prolonged period. Absorbed doses from external and/or neutron exposure used in the study were provided by MWDS-2008. Relative risk (RR) and excess relative risk per unit dose (ERR/Gy) were estimated based on maximum likelihood using AMFIT module of EPICURE software. Results: 4159 cataract diagnoses were verified in the study cohort of workers during 482217 person-years of follow-up. The majority of cataracts were diagnosed in cohort members included in the age group 61–70 years old in both males and females. The mean age at cataract diagnosis was 63.1 ± 0.2 years in males and 64.8 ± 0.2 years in females, respectively. RR of cataract incidence was statistically significant in all dose categories when compared to a reference category (0–0.25 Gy) and increased with increasing dose from external gamma-rays and was the highest in workers exposed to external gamma-rays at doses exceeding 2.0 Gy (1.61 95 % CI: 1,41–1,83). Significant linear association of cataracts with dose from external gamma-rays was observed with ERR/Gy = 0.28 (95 % CI: 0.20, 0.37). The risk estimate varied slightly with inclusion of additional adjustments for different non-radiation factors (smoking status and alcohol consumption, smoking index, hypertension, body mass index, severe myopia diagnosed). After adjusting for dose from neutrons ERR/Gy of external gamma-rays for cataracts increased considerably (0.31; 95 % CI: 0.22, 0.40). Significant ERR/Gy of external gamma-rays for senile cataract was revealed in both male and female workers of the study cohort, however the variations between the sexes were insignificant (p = 0.09). ERR/Gy of external gamma-rays for senile cataract was significant in all age groups except for workers under 40 years, but the differences among the age groups were insignificant (p > 0.5). Conclusion: Risk of senile cataract incidence in the cohort of Mayak PA workers, occupationally exposed to radiation over prolonged periods, was significantly associated with dose from external gamma-rays.