Dietary glycemic index and carbohydrate in relation to early age-related macular degeneration.

Background: Several dietary factors have been linked to age-related maculopathy (ARM), the early form of age-related macular degeneration, and there is reason to think that dietary carbohydrate may play a role in the development of ARM.
Objective: The purpose of the present study was to examine the relation between dietary carbohydrate quality, as measured by dietary glycemic index (GI) or total carbohydrate intake, and ARM.
Design: From the Nurses' Health Study, 1036 eyes from 526 Boston-area participants without a previous ARM diagnosis were included in the present study. The presence and degree of ARM were classified by the Age-Related Eye Diseases Study system. Long-term dietary information was based on data from an average of 4 food-frequency questionnaires collected over a 10-y period before the assessment of ARM. With eyes as the unit of analysis, we used a generalized estimating approach to logistic regression to estimate the odds ratios for ARM in a manner that accounted for the lack of independence between the 2 eyes from the same subject.
Results: After multivariate adjustment, dietary GI was related to ARM (specifically to retinal pigmentary abnormalities), whereas total carbohydrate intake was not. The odds ratio for ARM being in the highest tertile of dietary GI (> or =77.0) versus the lowest (<74.6) was 2.71 (95% CI: 1.24, 5.93; P for trend = 0.01). Neither dietary GI nor total carbohydrate intake was related to drusen.
Conclusion: Our results suggest that dietary GI may be an independent risk factor for ARM.