Objective: To provide 9-year incidence estimates of age-related macular degeneration (AMD) in a population of African descent.
Design: Population-based cohort study.
Participants: Two thousand seven hundred ninety-three participants (81% of eligible) after 9 years' follow-up.
Main outcome measures: Nine-year incidence of AMD-related features, based on fundus photographic gradings and/or clinical examinations.
Results: The overall incidence rate of early AMD was 12.6% (95% confidence interval [CI], 11.0%-14.1%), and that of late AMD was 0.7% (95% CI, 0.4%-1.1%). Both increased with age (P<0.05). For early AMD, incidence ranged from 10.7% at 40 to 49 years of age to 16.8% at > or =70 years. For late AMD, incidence increased from 0.1% to 2.3% in the same age groups. Late AMD was more likely to develop in eyes with pigment changes (risk ratio [RR], 5.8; 95% CI, 2.0-16.8) and retinal pigment epithelial atrophy (RR, 5.4; 95% CI, 1.9-15.8) at baseline. Crude RRs indicated significant associations of late AMD to elevated systolic blood pressure and diabetes history, but only the diabetes relationship was suggested after adjusting for age, with borderline statistical significance (age-adjusted RR, 2.7; P = 0.054).
Conclusions: Nine-year data on natural history indicate that early AMD is common in this population of African origin, although late AMD is infrequent. These long-term observations provide further evidence for the lower AMD risk in black populations compared with white populations.