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Background Individuals with early or intermediate stages of age-related macular degeneration (AMD) make up a large and growing segment of our elderly population. To advise these high-risk patients regarding preventive measures, we evaluated anthropomorphic, behavioral, and medical factors associated with progression to the advanced stages of AMD associated with visual loss. Methods The design was a prospective cohort study in a hospital-based retinal practice. The 261 participants were 60 years or older, with some sign of nonadvanced AMD and visual acuity of 20/200 or better in at least 1 eye. The average follow-up time was 4.6 years, and the total person-years of follow-up was 1198. Factors associated with rates of progression to advanced AMD were assessed by the Cox proportional hazards model. Outcome Measures Progression to geographic atrophy and neovascular disease. Results Higher body mass index (calculated as weight in kilograms divided by the square of height in meters) increased the risk for progression to the advanced forms of AMD. Relative risk (RR) was 2.35 (95% confidence interval[CI], 1.27-4.34) for a body mass index of at least 30, and 2.32 (95% CI, 1.32-4.07) for a body mass index of 25 to 29, relative to the lowest category ( P = .007 for trend). Higher waist circumference was associated with a 2-fold increased risk for progression (RR for the highest tertile compared with the lowest, 2.04; 95% CI, 1.12-3.72), with a significant trend for increasing risk with a greater waist circumference ( P = .02). Higher waist-hip ratio also increased the risk for progression (RR, 1.84; 95% CI, 1.07-3.15) for the highest tertile compared with lowest ( P = .02 for trend). More physical activity tended to be associated with a reduced rate of progression (25% reduction for 3 times per week vigorous activity vs none, P = .05 to P = .07). Relative risks for smoking ranged from 1.48 to 1.99, but were not statistically significant. Conclusions Results provide new information regarding modifiable factors for individuals with the early or intermediate stages of this disease. Overall and abdominal obesity increased the risk for progression to advanced AMD, and more physical activity tended to decrease risk. These preventive measures deserve additional research and greater emphasis.