Cataract incidence in the cohort of occupationally exposed workers

Abstract

Objective: To assess cataract incidence in the cohort of workers occupationally exposed to prolonged radiation. Material and Methods: Cataract incidence was studied in the cohort of workers of the first Russian nuclear enterprise — the Mayak, who were firstly employed at one of the main facilities (reactors, radiochemical and plutonium production plants) in 1948‑1958 and followed up to the end of 2008 (12210 persons). Total of 3100 cataract cases were registered in the study cohort. All cataract cases were reviewed and verified by experts; the study included only confirmed senile cataracts. All workers of the study cohort were exposed to external gamma-rays; mean cumulative dose from external gamma-rays was 0.91±0.01 Gy in males and 0.65±0.01 Gy in females. Statistical analysis provided non-standardized and standardized incidence rates per 100 000 workers. Standardization by sex and age was performed by indirect method using internal reference.Results: 2523 cases of senile cataract were included in the study. Mean age of cataract diagnosis was 62.88±0.26 years in males and 64.88±0.28 years in females. Standardized incidence rates of cataract in females were significantly higher as compared to males and increased with workers age. Comparison between the subcohorts of workers with / without diagnosed cataracts demonstrated that among workers with cataracts the proportions of the following groups of workers were significantly higher: workers employed before 1954; workers employed at reactors; smoking workers; workers with the smoking index exceeding 20 pack*years; workers who consumed alcohol; workers with excessive body weight; workers with glaucoma and arterial hypertension. Moreover the mean cumulative dose from external gamma-rays and / or neutron exposure was significantly higher in the subcohort of workers diagnosed with cataracts than that in the subcohort of workers free of the disease. The highest cataract incidence rates were revealed in workers of both sexes aged 60 and above. The cataract incidence rate was significantly associated with non-radiation risk factors (smoking, concomitant glaucoma and / or high myopia). No effect modification by body mass index, arterial hypertension and alcohol consumption status was observed for cataract incidence among members of the study worker cohort. Cataract incidence was significantly increased in workers exposed to external gamma-rays at cumulative dose > 1.0 Gy as compared to workers exposed at lower doses.Conclusion: The study revealed that cataract incidence in the cohort of occupationally exposed workers was associated with both non-radiation (sex, attained age, concomitant ocular pathology) and radiation (external gamma-rays) factors.

Keywords

• senile cataract
• incidence rates
• risk factors
• external radiation exposure