Prospective study of zinc intake and the risk of age-related macular degeneration

PURPOSE: Zinc is found in high concentrations in the retina and is hypothesized to reduce the risk of age-related macular degeneration (AMD). Any long-term benefit associated with dietary zinc intake has nor been evaluated. METHODS: We followed 66,572 women and 37,636 men who were greater than or equal to 50 years old and had no diagnosis of AMD or cancer. Zinc intake from food, multivitamins, and supplements was assessed with a semiquantitative food-frequency questionnaire at baseline (in 1984 for women and in 1986 for men) and repeated during follow-up (twice for women, once for men). RESULTS: During 10 years of follow-up for women and 8 years of follow-up for men, we confirmed 384 incident cases of AMD (195 cases of the early form and 189 cases of the late form) associated with a visual acuity loss of 20/30 or worse. After multivariate adjustment for potential risk factors, the pooled relative risk was 1.13 (95% confidence interval [CI], 0.82 to 1.57; p-value, test for trend, 0.74) among participants in the highest quintile of total zinc intake (energy-adjusted median; 25.5 mg/day for women and 40.1 mg/day for men) compared with those in the lowest quintile (energy-adjusted median; 8.5 mg/day for women and 9.9 mg/day for men). The relative risk for highest compared with lowest quintile was 1.04 (95% CI, 0.59 to 1.83; e-value, test for trend, 0.54) for zinc intake from food. Subjects who took zinc supplements had a pooled multivariate relative risk of 1.04 (95% CI, 0.75 to 1.45). CONCLUSIONS: In these two large prospective studies, moderate zinc intake, either in food or in supplements, was not associated with a reduced risk of AMD. Ann Epidemiol 2001;11:328-336, (C) 2001 Elsevier Science Inc. All rights reserved.