Dietary carbohydrate and the progression of age-related macular degeneration: a prospective study from the Age-Related Eye Disease Study.
BACKGROUND: Cross-sectional studies indicate that diets that provide a higher dietary glycemic index (dGI) are associated with a greater risk of age-related macular degeneration (AMD). No prospective studies have addressed this issue.
OBJECTIVE: The objective was to prospectively evaluate the effect of baseline dGI on the progression of AMD.
DESIGN: dGI was calculated as the weighted average of GIs from foods and was evaluated as being above or below the sex median (women: 77.9; men: 79.3) for 3977 participants aged 55-80 y (58% women) in the Age-Related Eye Disease Study. The 7232 eligible eyes without advanced AMD were classified into 1 of 3 AMD categories: group 1 (nonextensive small drusen), group 2 (intermediate drusen, extensive small drusen, or pigmentary abnormalities), or group 3 (large drusen or extensive intermediate drusen). With the use of multifailure Cox proportional-hazards regression, we modeled the time to the maximal progression to evaluate the relation between dGI and the risk of AMD.
RESULTS: Overall, the multivariate-adjusted risk of progression over 8 y of follow-up (x: 5.4 y) was significantly higher (risk ratio: 1.10; 95% CI: 1.00, 1.20; P = 0.047) in the high-dGI group than in the low-dGI group. The risk of progression for groups 1, 2, and 3 eyes was 5%, 8%, and 17% greater, respectively (P for trend < 0.001). The latter gives an estimate that 7.8% of new advanced AMD cases would be prevented in 5 y if people consumed the low-dGI diet.
CONCLUSION: Persons at risk of AMD progression, especially those at high risk of advanced AMD, may benefit from consuming a smaller amount of refined carbohydrates.