Nine-year incidence and risk factors for age-related macular degeneration in a defined Japanese population the Hisayama study.

PURPOSE: To estimate the 9-year incidence and risk factors for age-related macular degeneration (AMD) in a general Japanese population.

DESIGN: Population-based, cohort study.

PARTICIPANTS: In 1998, a total of 1775 Hisayama residents aged >or=40 years underwent a baseline eye examination. Of those, 1401 subjects (78.9%) took part in the follow-up eye examination in 2007 and were enrolled in the present study.

METHODS: At both time points, the characteristics of AMD were determined by grading color fundus photographs using the Wisconsin Age-Related Maculopathy Grading System.

MAIN OUTCOME MEASURES: Incident early and late AMD.

RESULTS: The age-standardized, 9-year cumulative incidence of early AMD was 10.0%, and that of late AMD was 1.4%. Men were found to have a significantly higher incidence of late AMD than women (age-adjusted odds ratio [OR], 2.97; 95% confidence interval [CI], 1.25-7.09). The incidence of both early and late AMD increased significantly with age. Multiple logistic regression analysis showed that older age (per 1 year; OR, 1.10; 95% CI, 1.05-1.16), smoking habits (OR, 3.98; 95% CI, 1.07-14.7), and higher circulating white blood cell (WBC) count (per 1000 cells/mm(3)) (OR, 1.38; 95% CI, 1.07-1.79) were significantly associated with the development of late AMD.

CONCLUSIONS: Our findings suggest that the 9-year incidences of late AMD are lower among the Japanese than among white people in Western countries, and it is higher than among black people. Smoking habits and higher circulating WBC count are significant risk factors for the development of late AMD in the Japanese.