Abstract
Purpose: :
To determine the effect of high-dose oral supplements of antioxidant vitamins and zinc, and age-related macular degeneration (AMD) on diabetic retinopathy (DR).
Methods: :
This analysis includes 235 participants (464 eyes) with diabetes enrolled in the Age-Related Eye Disease Study (AREDS). Persons with greater than 10 micro aneurysms and/or small retinal hemorrhages were excluded at baseline. Participants with varying stages of AMD were randomly assigned to receive: 1. antioxidants (vitamins C, E and beta carotene); 2. zinc (zinc oxide) and copper (cupric oxide); 3. antioxidants plus zinc; or 4. placebo. Treatment in this analysis is defined as AREDS formulation consisting of antioxidants, zinc or both. DR severity was measured by an independent photographic reading center using the Early Treatment Diabetic Retinopathy Study (ETDRS) severity scale. A non linear mixed effects model with a logit function incorporating the generalized estimation equations methodology was used to explore the relationship between the AREDS supplements and AMD severity with DR at the end of the AREDS clinical trial.
Results: :
In total, 398 (50%) had diabetes at baseline and 403 (50%) developed diabetes during follow-up. The median follow-up of the 235 participants included in this preliminary analysis was 5.3 years. The mean age of participants is 68.2±5 years at baseline and 47% are female. Of the 428 eyes with no DR at baseline, 33 (8%) developed DR (20 or worse on the DR severity scale) by the end of the clinical study. The odds of progression to DR was reduced yet did not reach statistical significance for those randomized to AREDS treatment compared to placebo (OR: 0.30; 95% CI: 0.08 - 1.14). The odds of progression was statistically significantly reduced for those with geographic atrophy (GA) or neovascular (NV) AMD compared to those with no or mild AMD (OR: 0.06; 95% CI: 0.005 - 0.85). Of the 464 eyes, 13 (3%) had a 2-step change on the DR severity scale by the end of the clinical trial. The odds for a 2-step progression were reduced but did not reach statistical significance for AREDS treatment and presence of GA or NV AMD (OR: 0.11; 95% CI: 0.01 - 1.22 and OR: 0.13; 95% CI: 0.005 - 3.19, respectively).
Conclusions: :
Although not reaching statistical significance, these preliminary results suggest an association between high-dose vitamin/mineral use and AMD with DR. Further analyses will be conducted and presented once the final fundus photographic gradings for all 801 participants with diabetes are completed.
Clinical Trial: :
www.clinicaltrials.gov NCT00000145
Keywords: diabetic retinopathy • antioxidants • age-related macular degeneration