Purpose: To describe the 6-year incidence of early and late age-related macular degeneration (AMD) and its associated factors in a representative large rural Chinese population.
Methods: A population-based longitudinal study was conducted in rural China from 2006 to 2007. In total, 6830 persons aged 30 years or older participated in the study. The 6-year follow-up study was performed between 2012 and 2013. The modified Wisconsin Age-Related Maculopathy Grading System (WARMGS) protocol in the Blue Mountains Eye Study was used as the AMD grading standard.
Results: Excluding 509 deceased subjects, 5394 (follow-up rate 85.3%) completed the follow-up. Among them, 5048 participants had gradable photographs of at least one eye at both examinations. The incidence of early and late AMD over 6 years was 4.2% (95% CI, 3.8%-4.7%) and 0.2% (95% CI, 0.2%-0.3%), respectively. In the multivariable analysis, per-year increase in age (P < 0.001; OR = 1.06; 95% CI, 1.04-1.07), male sex (P = 0.006; OR = 0.64; 95% CI, 0.47-0.88), and per-millimeter increase in axial length (P = 0.010; OR = 0.78; 95% CI, 0.63-0.94) at baseline were significantly associated with incident early AMD. Early AMD was not associated with systolic blood pressure, diastolic blood pressure, hypertension, diabetes, history of stroke, history of heart disease, body mass index, total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides, smoking status, refractive error, or corneal curvature radius. There were too few cases of late AMD for a valid statistical analysis of the risk factors.
Conclusions: The incidence of early and late AMD over 6 years in a rural Chinese population was 4.2% (95% CI, 3.8%-4.7%) and 0.2% (95% CI, 0.2%-0.3%), respectively. Age, sex, and axial length are relevant risk factors for early AMD in rural China.