(05-11-08) Dietary glycemic index and the risk of age-related macular degeneration 1,2,3

Shweta Kaushik, Jie Jin Wang, Victoria Flood, Jennifer Sue Ling Tan, Alan W Barclay, Tien Y Wong, Jennie Brand-Miller and Paul Mitchell
1 From the Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia (SK, JJW, VF, JSLT, and PM); the Centre for Eye Research Australia, University of Melbourne, Australia (JJW and TYW); the Human Nutrition Unit, Department of Molecular and Microbial Biosciences, University of Sydney, Sydney, Australia (VF, AWB, and JB-M); and the Department of Ophthalmology, National University of Singapore, Singapore, Republic of Singapore (TYW)

Background: Dietary factors are known risk factors for age-related macular degeneration (AMD)?the leading cause of visual loss among persons aged 65 y. High-glycemic-index diets have been hypothesized as a risk factor for AMD, but prospective data are unavailable.
Objective: The objective was to examine the association between dietary glycemic index and the 10-y incidence of AMD in the Blue Mountain Eye Study population.
Design: This was a population-based cohort study with 3654 participants ( 49 y) examined at baseline (1992?1994); 2335 patients were reexamined after 5 y and 1952 after 10 y. The Wisconsin System was used to grade 10-y incident early and late AMD from retinal photographs. A food-frequency questionnaire was used to collect dietary information at baseline, and an Australian database was used to calculate the mean glycemic index.
Results: Over 10 y, 208 of 1810 persons (cumulative incidence: 14.1%) developed early AMD. After age, smoking, other risk factors, and dietary constituents were adjusted for, a higher mean dietary glycemic index was associated with an increased 10-y risk of early AMD in a comparison of quartiles 1 and 4 [relative risk (RR): 1.77; 95% CI: 1.13, 2.78; P for trend = 0.03]. Conversely, a greater consumption of cereal fiber (RR: 0.68; 95% CI: 0.44, 1.04; P for trend = 0.05) and breads and cereals (predominantly lower glycemic index foods such as oatmeal) (RR: 0.67; 95% CI: 0.44, 1.02; P for trend = 0.03) was associated with a reduced risk of incident early AMD. No relation was observed with late AMD.
Conclusions: A high-glycemic-index diet is a risk factor for early AMD?the recognized precursor of sight-threatening late AMD. Low-glycemic-index foods such as oatmeal may protect against early AMD.

Source: American Journal of Clinical Nutrition, Vol. 88, No. 4, 1104-1110, October 2008

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