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M Cusick, EY Chew, TE Clemons, R Klein, BE K Klein, LD HubbardAREDS Research Group; Effect of Antioxidant and Zinc Supplements on Development of Diabetic Retinopathy in the Age-Related Eye Disease Study (AREDS) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1909.
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Purpose: To determine the effect of high-dose antioxidant and zinc supplements on diabetic retinopathy. Methods: Participants in AREDS were randomly assigned to receive daily tablets containing (1) antioxidants (500 mg vitamin C, 400 IU vitamin E, and 15 mg beta carotene); (2) 80 mg zinc as zinc oxide and 2 mg copper as cupric oxide; (3) antioxidants plus zinc; or (4) placebo. Participants with diabetes at enrollment were included in this analysis. Diabetic retinopathy, assessed from 3-field stereo color fundus photographs by an independent photograph reading center, was defined as the presence of at least hemorrhages and/or microaneurysms. Eyes with diabetic retinopathy or advanced age-related macular degeneration at baseline were excluded. The Cox proportional hazards model was used to explore the relationship between use of the AREDS supplements and the development of diabetic retinopathy. Results: 257 participants were eligible for analysis. Median follow-up was 6.0 years. The mean age of participants at baseline was 68.9 years (SD 4.8), the mean duration of diabetes was 9.6 years, and 43% were female. Thirty-seven percent of the eligible participants developed diabetic retinopathy. The 5-year Kaplan-Meier estimates for development of diabetic retinopathy were 35% for placebo, 32% for antioxidants alone, 32% for zinc alone and 28% for antioxidants plus zinc. The risk ratios (RR), adjusted for baseline AMD category, for treatment versus placebo were: antioxidants alone, RR= 0.86 (95% CI: 0.49-1.52); zinc alone, RR= 0.91 (95% CI: 0.50-1.65); and antioxidants plus zinc, RR=0.76 (95% CI: 0.42-1.37). An analysis adjusted for age, sex, race, baseline smoking status, and duration of diabetes did not materially alter the size or direction of these RR estimates. Conclusion: Although not statistically significant, relative risk estimates are all in the direction of decreased risk of development of diabetic retinopathy in persons with diabetes assigned to high-dose antioxidant/zinc supplements, suggesting further investigation is warranted.
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