Age-related macular degeneration (AMD) is a major cause of blindness in the U.S., especially among individuals over age 65. Animal studies have suggested that antioxidants may play a role in preventing or retarding AMD. the goal of the proposed study is to test this hypothesis among humans as part of the ongoing Physicians' Health Study (PHS), a randomized, double-blind, placebo-controlled clinical trial of aspirin in reducing cardiovascular mortality and beta-carotene supplementation (50mg every other day) in reducing cancer incidence among 22,071 male U.S. physicians aged 40 to 84 years. The proposed study will utilize the PHS database to assess the effect of beta-carotene supplements on AMD development. Thus, it will be possible to provide a valid test of the beta-carotene-AMD hypothesis without the expense of funding a large clinical trial. Baseline information was collected on the participants in 1982, and beginning with the 84-month follow-up, annual questionnaires will request information on diagnoses of AMD. All reported diagnoses of AMD will be confirmed by medical record review. It is expected that by the end of the follow-up period (June, 1990), there will be approximately 600 incident cases of AMD. The primary analysis will be incidence of AMD in the beta-carotene and placebo groups. In addition, Cox proportional hazards models will be used to determine whether there is a difference in time to AMD diagnosis. The incidence of AMD will also be investigated prospectively for other antioxidants (vitamins A, E, C, selenium). Factors that have been suggested to increase risk of AMD and other potential risk factors will also be investigated using nested case-control methods, matching four controls (for age and time of randomization) to each AMD case. These factors include blood pressure, blood cholesterol, cigarette smoking, alcohol use, history of cardiovascular disease, diabetes, height, and body mass index, iris and skin color, and sunlight exposure.
